Analytical Methods (v.5, #16)
Front cover (3763-3763).
Inside front cover (3764-3764).
Contents list (3765-3784).
The evolution of chemometrics by Richard G. Brereton (3785-3789).
Classification tools in chemistry. Part 1: linear models. PLS-DA by Davide Ballabio; Viviana Consonni (3790-3798).
The common steps to calibrate and validate classification models based on partial least squares discriminant analysis are discussed in the present tutorial. All issues to be evaluated during model training and validation are introduced and explained using a chemical dataset, composed of toxic and non-toxic sediment samples. The analysis was carried out with MATLAB routines, which are available in the ESI of this tutorial, together with the dataset and a detailed list of all MATLAB instructions used for the analysis.
Direct analysis of potentially genotoxic impurities by thermal desorption-field asymmetric waveform ion mobility spectrometry-mass spectrometry by Robert W. Smith; James C. Reynolds; Sze-Ling Lee; Colin S. Creaser (3799-3802).
Thermal desorption has been combined with field asymmetric waveform ion mobility spectrometry and mass spectrometry for the rapid, direct analysis of isobaric potentially genotoxic impurities (PGIs) in a surrogate active pharmaceutical ingredient. FAIMS-selected PGIs were detected with limits of quantification <0.2 ppm, below the threshold of toxicological concern, with %RSD <8.4%, at the 1 ppm level.
Platinum nanoflower-based catalysts for an enzyme-free electrochemical immunoassay of neuron-specific enolase by Xiaohong Fu; Rong Huang; Jiexue Wang; Xueru Feng (3803-3806).
Platinum nanoflowers (PtNFs) were for the first time employed as a label for a highly efficient, enzyme-free electrochemical immunoassay of neuron-specific enolase (NSE, as a model) by coupling a nanocatalyst-based electrocatalytic reaction with catalytic recycling of self-produced reactants.
Exhaled breath acetone for therapeutic monitoring in pneumonia using selected ion flow tube mass spectrometry (SIFT-MS) by Juzheng Huang; Sacheen Kumar; Aran Singanayagam; Peter M. George; Onn Min Kon; Masao Takata; George B. Hanna (3807-3810).
Exhaled breath analysis of volatile organic compounds (VOCs) has great potential in terms of measuring physiological response to treatment. Exhaled breath acetone was measured in patients with community acquired pneumonia for the duration of their in-hospital treatment using Selected Ion Flow Tube-Mass Spectrometry (SIFT-MS). A positive correlation was observed between exhaled breath acetone concentrations and same-day serum C-reactive protein (CRP) levels. Exhaled breath acetone concentrations and CRP levels decreased in the range of 76–90% and 67–80%, respectively, from the day of admission to the day of discharge. This proof of concept study demonstrates the potential of SIFT-MS exhaled breath analysis as a non-invasive tool for clinical therapeutic monitoring.
Nanoparticle modified QCM-based sensor for lipase activity determination by Margarita Stoytcheva; Roumen Zlatev; Zdravka Velkova; Gisela Montero (3811-3815).
A highly sensitive lipase activity sensor was developed and tested. It is based on the application of SiO2 nanoparticle loaded olive oil as a lipase substrate, deposited on a QCM crystal. The heavier nanoparticles’ release during the substrate enzymatic degradation causes a QCM frequency response enhancement proportional to the nanoparticle/substrate mass ratio.
Multiplexed quantification of surface-bound proteins on gold nanoparticles by Seol-Hye Hong; Min ji Kim; Joong-Hoon Ahn; Woon-Seok Yeo (3816-3818).
In this report, we present a simple, cost effective, and less laborious method for the absolute and multiplexed quantification of surface-bound proteins using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) and the isotope-labeled internal standards (ISs).
‘It's not easy being green’: a spectroscopic study of green pigments used in illuminated manuscripts by Paola Ricciardi; Anuradha Pallipurath; Kristine Rose (3819-3824).
This study explores the use of green pigments and mixtures in manuscript illumination, drawing upon experimental evidence derived from a non-invasive spectroscopic survey of green pigments used in 31 bound manuscripts and 23 manuscript cuttings or single folios in the collections of the Fitzwilliam Museum in Cambridge, UK. Analytical investigations were carried out on green-coloured areas by visible and near-infrared fibre optic reflectance spectroscopy (FORS), at times supplemented by X-ray fluorescence (XRF). FORS spectra can easily be acquired in great numbers and without subjecting the manuscripts to any physical strain, making this technique especially suitable for analytical surveys of valuable and fragile objects. Despite some drawbacks, its use in combination with XRF often provides a relatively complete characterisation of pigments and mixtures, particularly when FORS analysis is extended into the shortwave-infrared range (to 2500 nm). The experimental results are examined in light of the recipes for green pigments found in medieval technical treatises. The outcome is a contextualized study with a focus on French illumination between the 13th and the 16th century, but allowing for comparisons with contemporary materials of different geographic origin.
Determination of eight artificial sweeteners in wastewater by hydrophilic interaction liquid chromatography-tandem mass spectrometry by Maroula G. Kokotou; Nikolaos S. Thomaidis (3825-3833).
The development of a method for the simultaneous determination of eight artificial sweeteners, namely aspartame (ASP), alitame (ALI), neotame (NEO), acesulfame (ACS), saccharin (SAC), cyclamate (CYC), sucralose (SCL) and neohesperidin dihydrochalcone (NHDC), under hydrophilic interaction liquid chromatography (HILIC) conditions is presented herein. The ionization of all the compounds was achieved by negative electrospray. Two silica-based columns, a fully porous (XBridge HILIC) and a fused-core one (Kinetex HILIC), were compared. For HILIC optimization, the effect of the following parameters was studied: the mobile phase, column temperature, pH and ionic strength of the ammonium formate buffer. The optimized mobile phase was 5 mM ammonium formate buffer pH 3.5–methanol–acetonitrile (15/10/75 v/v), with a flow rate of 100 μL min−1 at 50 °C. The asymmetry factor of the peaks was lower on the Kinetex HILIC column than that on the XBridge HILIC. The predominant retention mechanism of all the analytes on silica columns seems to be partition to the aqueous layer. The method was validated in tap water and wastewater samples using Kinetex HILIC. Three deuterated internal standards were used, one for each category of sweeteners (dipeptides, sulfamates and sugars). The instrumental limits of detection ranged from 0.24 (SAC) to 4.4 (SCL) μg L−1. The recoveries in influent samples ranged from 39% (CYC) to 97% (NEO), while recoveries were better for the other two matrices. Inter-day precision (%RSD, n = 6) ranged from 4.2% (SAC) to 20% (ALI) in influent samples. The method was applied to influents and effluents from the wastewater treatment plant of Athens for seven consecutive days and high levels of sucralose and sulfamates were found.
Rapid electrochemical detection of ferulic acid based on a graphene modified glass carbon electrode by Yanli Zhang; Yanpei Liu; Zhongming Yang; Yingcai Yang; Pengfei Pang; Yuntao Gao; Qiufen Hu (3834-3839).
A graphene nanosheet modified glassy carbon electrode (GN/GCE) is proposed as a voltammetric sensor for ferulic acid with good sensitivity, selectivity and reproducibility. The sensor oxidizes ferulic acid in a surface-confined and quasi-reversible process, as revealed by cyclic voltammetry. The results show more favorable electron transfer kinetics than for a bare glassy carbon electrode (GCE). The linear response of the sensor is from 5 × 10−7 to 5 × 10−5 M with a detection limit of 2 × 10−7 M (S/N = 3). Graphene, as a single nanosheet, shows more favorable electrochemical activity and should be a more robust and advanced carbon electrode material, which provides a promising platform for electrochemical sensors and biosensors. The method was successfully applied to the detection of ferulic acid in pharmaceutical tablets with satisfactory results.
Applications of voltammetric ion selective electrodes to complex matrices by Alexander R. Harris; Jie Zhang; Robert W. Cattrall; Alan M. Bond (3840-3852).
The practical application of two different voltammetric ion selective electrodes (VISE) to measure ion activity in complex solutions has been explored. 7,7,8,8-tetracyanoquinodimethane (TCNQ) and tetrathiafulvalene (TTF) microcrystals adhered to an electrode surface act as a low selectivity voltammetric ion sensor. Resistance drop effects and pH artifacts were minimised by the addition of an “innocent” supporting electrolyte (buffer) to the analyte solution. In this format, addition of an ionophore to improve selectivity resulted in a reduction in current magnitude, due to competition for the ion. In contrast, voltammetry of a thin film containing a redox active species, electrolyte, ionophore and membrane solvent provides a highly selective ion sensor. Choice of ionophore was shown to affect the upper concentration detection limit. Use of ionic liquids as a combined membrane solvent and electrolyte was demonstrated. Methods to attach both VISE types to low-cost screen-printed electrodes have been explored. Various potential referencing techniques were also investigated. Both the microcrystal and thin film VISEs could be used to determine ion activity in complex solutions, as demonstrated in seawater, beverages, plasma and whole blood. Dissolved oxygen does not need to be removed, as it does not affect the response. However calibration methods are important for sensor accuracy and issues relating to electrode fouling must be addressed.
Fluorescent silver nanoclusters embedded with polymer nanoparticles for sensing copper ions by Yang Li; Xumei Wang; Gang Chen; Shuping Xu; Weiqing Xu (3853-3857).
Novel fluorescent silver nanoclusters prepared by core/shell polymer nanoparticles as templates were applied to detecting copper (Cu2+) ions in aqueous solution based on fluorescence quenching. Changes in fluorescence intensity allow a quick response and sensitive detection of Cu2+ ions at concentrations as low as 20.9 nM. Also, excellent selectivity of Cu2+ ions was observed in anti-interference experiments against other metal cations. These fluorescent silver nanoclusters embedded with the polymer nanoparticles have the advantage of long-term stability and good water solubility, which are suitable to be combined with microfluidic systems for real-time sensing of Cu2+ ions. Detection in real water samples by our method also presented good results in the experiments, showing the potential of silver nanoclusters embedded with polymer nanoparticles as a practical analytical tool.
NIR reflectance determination of warfarin in a solid preparation commercialized at different API mass proportions by J. Arruabarrena; J. Coello; S. Maspoch (3858-3863).
Due to the need of accurate control of their therapeutic doses, warfarin-containing medicines are marketed in preparations with low, but different warfarin contents. A single near infrared reflectance procedure is proposed for warfarin determination in four different doses of a commercial preparation, with PLS as multivariate calibration tool and with an active pharmaceutical ingredient proportion ranging from one to five per cent of mass tablet. A mixed calibration sample set, composed of commercial samples and laboratory compacted tablets was prepared. In order to achieve suitable accuracy and precision, the difference in scattering between laboratory and commercial tablets was reduced by studying the effect of the compaction pressure. Also a spectral pre-treatment was applied, consisting of a second derivative followed by the Standard Normal Variate (SNV) normalization of the derivative spectra. The wavelength range 1480–1560 nm had to be deleted since a shift of an absorption band of lactose was detected after tablet compaction under laboratory conditions. No significant differences were found between the NIR prediction and HPLC reference data of the validation sample set.
Nanodiamonds assisted-cloud point extraction for the determination of fluoranthene in river water by Encarnación Caballero-Díaz; Bartolomé M. Simonet; Miguel Valcárcel (3864-3871).
The classic cloud point extraction has been modified by the inclusion of nanodiamonds and applied to the extraction–preconcentration of fluoranthene from river water. The effects of ionic strength and surfactant concentration, process temperature, incubation time, nanoparticle type and concentration and elution conditions were investigated in depth. The effect of the carbon nanoparticles (CNPs) on the performance of the conventional cloud point scheme enabled the formation of two phases in a relatively short time and without temperature requirements. Experiments carried out under optimized conditions but in absence of nanoparticles were unsuccessful in terms of phase separation and consequently, the nanoparticles are indispensable to the analytical performance. The work developed here, confirms the versatility of the CNPs to be introduced in diverse sample treatment processes, resulting very interesting to investigate in each case their impact on the performance of the process. The application of the proposed method followed by fluorimetric detection enabled the determination of fluoranthene in spiked river water providing a good relative standard deviation (RSD) (6.6%, n = 3) and acceptable recovery values (>65%).
A layer-by-layer tyrosinase biosensor for assay of carboxylesterase and neuropathy target esterase activities in blood by Larisa V. Sigolaeva; Galina V. Dubacheva; Marya V. Porus; Arkadi V. Eremenko; Elena V. Rudakova; Galina F. Makhaeva; Rudy J. Richardson; Ilya N. Kurochkin (3872-3879).
A tyrosinase-based phenol biosensor was formed via layer-by-layer (LBL) deposition of poly(dimethyldiallylammonium chloride) (PDDA) and tyrosinase onto polished graphite, followed by glutaraldehyde (GA) crosslinking. The PDDA/tyrosinase/GA graphite-substrate biosensor exhibited good reproducibility (6% relative SD for 1 × 10−5 M phenol, n = 10) and high sensitivity (6 nM detection limit, S/N = 3). The low detection limit enabled phenol measurements in highly diluted blood samples, which also minimized interference from extraneous (non-analyte) substances in blood (e.g., adrenaline, ascorbate, glucose, l-tyrosine, and urate). Applicability of the biosensor to analysis of carboxylesterase (CaE) and neuropathy target esterase (NTE) activities in mouse and human blood was demonstrated, and parallel biosensor and spectrophotometric CaE analyses were carried out 1 h after intraperitoneal injection of mice with the model dialkylphosphate, (C2H5O)2P(O)OCH(CF3)2 (DEHFPP). Dose-related inhibition of CaE activity was observed, yielding ED50 values [mean (95% CI) (n)] of 25.5 (23.2, 28.0) mg kg−1 (6) and 21.1 mg kg−1 (18.9, 23.5) (4) for spectrophotometric and electrochemical assays, respectively. Although the ED50 values were significantly different from each other (p < 0.007), excellent correlation between biosensor and spectrophotometric measurements was found (r = 0.99), indicating that the differences between the two methods are systematic and providing validation of the biosensor assay.
Pyridyl- and benzimidazole-based ruthenium(iii) complex for selective chloride recognition through fluorescence spectroscopy by Hemant Sharma; Hernández J. Guadalupe; Jayanthi Narayanan; Herbert Hofeld; Thangarasu Pandiyan; Narinder Singh (3880-3887).
Three ruthenium(ii) and (iii) metal complexes of the compositions ([Ru(1)(Cl)(PPh3)]+ (4), ([Ru(2)(Cl)(PPh3)]+ (5) and ([Ru(3)(Cl)(H2O)]2+ (6) have been synthesized from oligodentate pyridyl-(1) and benzimidazole ligands (2–3) and structurally characterized. Our investigations revealed that if the coordination sphere of the metal ion carries a strong coordinating PPh3 ligand (complexes 4 and 5), the framework was not suitable for anion binding at all. However, when coordination of solvent (H2O) to the metal centre occurred instead (complex 6), a receptor for anion recognition through fluorescence spectroscopy could be generated. This allowed us to develop a sensor for the selective recognition of chloride over several other anions. In order to screen potential applications, the sensor was tested for the determination of chloride concentration in a series of four commercially available oral rehydration salts, giving excellent agreement with the values reported by the corresponding manufacturer. The detection limit was established to be 5 μM.
Biotin labeling and receptor analysis of huwentoxin-I by Yi-Zhong Yan; Hui Liu; Rong Lv; Sha Huang; Ji-Rong Wang; Tian-Yao Guo; Qiong Zhou; Xian-Chun Wang (3888-3894).
Huwentoxin-I (HWTX-I) is the highest content peptidic neurotoxin in the crude venom of spider Selenocosmia huwena. This toxin blocks the nerve–muscle conduction of isolated phrenic nerve–hemidiaphragm preparation reversibly, with the action site in the presynaptic membrane. In order to further investigate the action mechanism of HWTX-I, the present work optimized the experimental conditions for the biotin labeling of HWTX-I and used the site-selectively biotinylated toxin to affinity purify and identify its receptor proteins from the plasma membrane in rat phrenic nerve–diaphragm synapses. The experiments demonstrated that when the biotinylation reagent reacted with HWTX-I at a molar ratio of 2 : 1 on ice for 2 h, most HWTX-I molecules were labeled by a single biotin group, with a yield of 57%. Tandem mass spectrometry and electrophysiological experiments indicated that the single biotin labeling occurred at the Lys13 residue of HWTX-I and this biotinylation did not significantly affect the bioactivity of HWTX-I. After the affinity purified protein fraction was ultrafiltered, digested with trypsin and analyzed by CapLC-MS/MS, several membrane proteins including voltage-gated calcium channel proteins that HWTX-I potentially interacted with were identified and their roles in the action mechanism of HWTX-I were discussed.
Sensitive voltammetric sensor for bergenin based on poly(l-lysine)/graphene modified glassy carbon electrode by Yinfeng Li; Jie Liu; Ge Song; Kunjing Li; Kai Zhang; Baoxian Ye (3895-3902).
A sensitive and novel electrochemical sensor for detection of bergenin by linear sweep voltammetry (LSV) is presented. This sensor was fabricated by dripping well-dispersed graphene onto glassy carbon electrode (GCE) surface firstly, and then poly(l-lysine) films were subsequently electropolymerized on it to prepare poly(l-lysine)/graphene/GCE. The dynamic detection range of this sensor to bergenin was 4.0 × 10−8 to 5.0 × 10−6 mol L−1 and 6.0 × 10−6 to 1.7 × 10−5 mol L−1, with the detection limit of 1.0 × 10−8 mol L−1. A new voltammetric method for determination of bergenin was erected and shows high sensitivity and selectivity, wider linear relationship, very easy surface update and good stability. The proposed sensors were tested for bergenin detection in pharmaceutical tablets with high accuracy and satisfactory recovery results was obtained. In addition, the oxidation mechanism is proposed and discussed, which could be a reference for the pharmacological action of bergenin in clinical studies.
Magnetic solid-phase extraction to preconcentrate ultra trace amounts of lead(ii) using modified-carbon nanotubes decorated with NiFe2O4 magnetic nanoparticles by Ali A. Ensafi; Sedigheh Rabiei; Behzad Rezaei; Ali R. Allafchian (3903-3908).
Here, multiwalled carbon nanotubes decorated with NiFe2O4 nanoparticles were synthesized by a simple reaction. Then, the nanoparticles were modified with 3-(trimethoxysilyl)-1-propanthiol. The modified-multiwalled carbon nanotubes decorated with NiFe2O4 nanoparticles were applied as a solid-phase extraction (SPE) sorbent for the extraction of ultra trace amounts of Pb(ii) from water samples. Detection in this technique was performed by flame atomic absorption spectrometry. The influences of effective parameters on the extraction efficiency were studied. The best results were obtained at pH 6.0 (acetate–borate buffer) with 2.0 mL eluent solution of 1.5 mol L−1 nitric acid and an extraction time of 30 min. The detection limit was 0.5 ng mL−1 Pb(ii) with a precision of 2.3–4.1%. The effects of matrix ions present in natural waters and some transition metals on the recoveries of the analyte ions were also examined in model solutions. Finally, the proposed method was used for the measurement of Pb(ii) in water from the Shiraz Khoshk river (Shiraz, Iran), food, and industrial waste water from Isfahan's Mobarakeh Steel Company.
An efficient fluorescence turn-on probe for Al3+ based on aggregation-induced emission by Tian-Tian Wei; Jing Zhang; Guo-Jiang Mao; Xiao-Bing Zhang; Zhao-Jin Ran; Weihong Tan; Ruqin Yu (3909-3914).
Aggregation-induced emission (AIE) dyes show different emission mechanism from traditional dyes, which were found to be nonluminescent in the solution state and emissive in the aggregate state, and have been well employed to design turn-on fluorescent probes for various targets. In this paper, we report for the first time a tetraphenylethylene-based AIE probe 1 for Al3+, which employed two diethylenetriamine units as the recognition ligand for Al3+. In the presence of Al3+, a large fluorescence enhancement was achieved for probe 1, which together with the low background fluorescence of free probe 1 allow for high sensitivity for Al3+, with a dynamic range from 2.0 × 10−6 to 1.1 × 10−5 M observed, and a detection limit of 5 × 10−7 M for Al3+. The proposed probe shows high selectivity to Al3+. UV-vis absorption spectra experiments and dynamic light scattering measurements were performed to verify the AIE sensing mechanism of probe 1. Moreover, a 1 : 1 stoichiometry was estimated for the 1–Al3+ complex via fluorescence Job's method.
Electrocatalytic oxidation of formaldehyde on direct electrodeposited graphene–platinum nanoparticles composites electrode by Yanan Chen; Xiaohui Liu; Wen Zhang; Yao Zhang; Lijun Li; Zhenzhu Cao; Hong Wang; Gan Jia; Yanfang Gao; Jinrong Liu (3915-3919).
The one-step electrochemical deposition of highly dispersed platinum nanoparticles on graphene to fabricate a new Pt/EG/GC modified electrode for formaldehyde determination in aqueous solution. Catalyst surface morphology was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM), the composition analysis was carried out on energy-dispersive X-ray spectroscopy (EDS). The electrochemical performances of the electrode were investigated by cyclic voltammetry, and clear amperometric responses were obtained in the scan process. The correlation coefficient was 0.998 of the linear relation between current values and concentrations, the Pt/EG/GC electrode exhibited a low limit of detection (0.04 mM), high sensitivity (0.0162 mA mM−1) and long working life. These characteristics make the Pt/EG/GC electrode appropriate for the formaldehyde determination based on formaldehyde electric catalytic oxidation.
Ultrasound-assisted cloud point extraction for the determination of sulfonamides in honey samples by fluorescence spectrophotometry by Fang Yu; Chang Liu; Yuhong Guo; Yaling Yang (3920-3926).
An ultrasound-assisted cloud point extraction (UA-CPE) method using nonionic surfactant nonylphenol ethoxylate (NP-7) as the extractant was developed for determination of two sulfonamides (SAs, sulfadiazine sodium and sulfamerazine) in honey samples. The procedure was based on the derivatization SAs in honey with fluorescamine yielding fluorescent complexes, which were extracted into the surfactant-rich phase and analyzed by molecular fluorescence spectrophotometry. The polar of SAs of derivatives was reduced and strong fluorescence was produced at λex = 410 nm. Variable parameters affecting the derivatization and UA-CPE procedure were evaluated and optimized. The calibration graph was linear from 10 to 10 000 ng mL−1 with coefficient of determination more than 0.9991. The limits of detection (LOD) were 0.5 ng mL−1 for sulfadiazine sodium and 5.0 ng mL−1 for sulfamerazine with the relative standard deviations of the method ranging from 2.2% to 4.1%. Recoveries of the compounds on spiked honey samples at fortified level of 1 μg mL−1 were 92.2% for sulfadiazine sodium and 84.1% for sulfamerazine, respectively. Therefore, the developed method is practical and reliable, with potential application to determine the content of SAs in honey samples.
Label-free selective detection of coralyne due to aptamer–coralyne interaction using DNA modified SiO2@Au core–shell nanoparticles as an effective SERS substrate by Yilin Lu; Qing Huang (3927-3932).
A label-free approach to the detection of coralyne using aptamer modified silica–Au/core–shell nanoparticles (denoted as SiO2@Au core–shell nanoparticles) through surface enhanced Raman scattering (SERS) spectroscopy was proposed. The silica–Au/core–shell colloids were synthesized and immobilized on a quartz substrate, and a single-stranded DNA (ssDNA) oligonucleotide designed as an aptamer for coralyne, namely, 5′-SH-(CH2)6-AAAAAAAAAAAAAAAA-3′, was covalently attached onto the Au nanoshells. The aptamer, with one end on the Au surface, changed conformation upon conjugation with target coralyne, which correspondingly caused changes in the intensity of the Raman band at 1376 cm−1 and the ratio of the Raman intensity at 736 cm−1 to the Raman intensity at 1319 cm−1. The intensity ratio increased with the amount of coralyne added, which therefore allowed the measurement coralyne in a selective and quantitative way, reaching a detection limit as low as 0.1 µM.
A sensitive, rapid chemiluminescence ELISA for the detection of 1, 4-bisdesoxycyadox residue in chicken muscle and liver by Jianying Fu; Yanying Wang; Juan Cao; Ziniu Yu; Jibin Zhang (3933-3941).
A rapid system for 1, 4-bisdesoxycyadox (Cy4) detection in chicken breast muscle and liver using a highly sensitive luminol hydrogen peroxide-based chemiluminescence enzyme-linked immunosorbent assay (CL-ELISA) was developed. Cy4-specific monoclonal antibodies (Mab) were prepared. The Cy4 Mab dilution ratios, coating antigen (Cy4–OVA) concentration, blocking concentration, immunoreaction time and CL reaction time were optimized. The specificity of the assay was assessed by determining the cross-reactivity with the Cy4 parent drug Cyadox (CYX) and its related analogues and metabolites. For this method, the limit of detection was 0.007 ng mL−1, the linear range (IC20–IC80) was 0.027–67.673 ng mL−1, the intra-assay and inter-assay precisions were <10% and <15%, respectively, and the recovery was 65.46–101.33%. When chicken breast muscle and liver were examined by CL-ELISA and high performance liquid chromatography, the results of the two techniques correlated well, indicating that the CL-ELISA method was suitable for the screening and quality detection of veterinary drug residues in animal tissues.
BSA-protected gold nanoclusters as fluorescent sensor for selective and sensitive detection of pyrophosphate by Jia-Ming Liu; Ma-Lin Cui; Shu-Lian Jiang; Xin-Xing Wang; Li-Ping Lin; Li Jiao; Li-Hong Zhang; Zhi-Yong Zheng (3942-3947).
Gold nanoclusters (AuNCs) protected by bovine serum albumin (BSA) can emit red photoluminescence under illumination by ultraviolet light. The luminescence of the BSA–AuNCs was quenched when Cu2+ chelated with glycine in the BSA chain and generated BSA–AuNCs–Cu2+, while the luminescence of the BSA–AuNCs restored when pyrophosphate ion (P2O74−, PPi) was added and chelated with Cu2+, resulting in Cu2+ being removed from the surface of BSA–AuNCs. Bearing this in mind, herein we present a novel BSA–AuNCs–Cu2+ fluorescent sensor for PPi detection. This environmentally-friendly, simple, rapid and selective fluorescent sensor possesses a wide linear range (0.16–78.1 μM) and a high sensitivity (the limit of detection (LD) is 0.083 μM), which could also determine PPi in the effluent of copper plating with the results consistent with those obtained by absorptiometry. Furthermore, the morphologies of BSA–AuNCs, BSA–AuNCs–Cu2+ and BSA–AuNCs–Cu2+-PPi were characterized by high resolution transmission electron microscopy (HRTEM). The mechanism of the proposed assay for PPi detection has been discussed.
Urine adulteration: can bleach be used to mask MDMA use? by Annie Q. N. Pham; Tamsin Kelly; Shanlin Fu (3948-3955).
Concerns regarding specimen integrity have long been a major issue of urine drug testing due to acts of urine adulteration. At a high concentration, in vitro urine adulteration using sodium hypochlorite (bleach) produced false-negative results for 3,4-methylenedioxymethamphetamine (MDMA) in CEDIA® immunoassay screening with strong negative readings. However, these strong negative readings may act as a warning sign for further investigation of the sample where the detection of a unique marker in the form of N-chloroMDMA will suggest urine adulteration via bleach. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) identified N-chloroMDMA is a major product formed between hypochlorite and MDMA in urine. N-ChloroMDMA was found stable at 4 °C for at least 10 h, but decomposed over time at room temperature (20 °C) with MDMA being identified as one of its main decomposition products.
Regional discrimination of oysters using laser-induced breakdown spectroscopy by Charlemagne A. Akpovo; Jorge A. Martinez Jr; Dawn E. Lewis; John Branch; Alexander Schroeder; Maurice D. Edington; Lewis Johnson (3956-3964).
It is well known that eastern oysters (Crassostrea virginica) are bio-indicators and can be used to determine the elemental composition of an estuarine system. Laser-induced breakdown spectroscopy (LIBS) has been successfully used for the detect of trace elements in various environmental matrices. In this work, LIBS was used to characterize oysters collected from a total of six sites in two different coastal estuarine reserves – Grand Bay, Mississippi (4 sites) and Apalachicola Bay, Florida (2 sites). Multiple ionic and neutral elemental species of Al, C, Ca, Cu, Fe, K, Mg, Na, Si, Sr, and Zn were observed through LIBS spectral analysis of the harvested oysters. Principal component analysis, discriminant function analysis, and hierarchical cluster analysis were applied to a data matrix of identified elemental lines resulting in intra- and inter-site clustering of the oysters according to their geographical origin.
Naked-eye detection of Cys using simple molecular systems of curcumin and Hg2+ by Fenghua Geng; Yongxiang Wang; Peng Qu; Yintang Zhang; Hui Dong; Maotian Xu (3965-3969).
A sensing ensemble for cysteine was assembled conveniently by simply mixing curcumin (Cur) and Hg2+ in buffered acetonitrile/HEPES (10 mM, 7/3, v/v, pH 7.4) solutions. In the ensemble, Hg2+ serves as the receptor, and Cur functions as the indicator in sensing the analyte. The detection can be performed either spectroscopically, by the decrease of the UV-Vis absorbance at 430 nm and the increase of the UV-Vis absorbance at 355 nm, or visually by the color change from colorless to yellow upon addition of an aqueous solution of the analyte to the solution of the ensemble.
Development of a HPLC-MS/MS confirmatory method for the simultaneous determination of amphenicols in baby formulas using molecularly imprinted polymers by Rocío Barreiro; Mónica Díaz-Bao; Patricia Regal; José M. Miranda; Alberto Cepeda (3970-3976).
Chloramphenicol (CAP) is a broad-spectrum bacteriostatic antibiotic commonly used in veterinary medicine. However, toxic effects in humans such as Grey syndrome, bone marrow suppression, and fatal aplastic anaemia have been described. As a consequence, the use of CAP in foodstuffs has been banned within the European Union since 1994 and no maximum residue limit (MRL) has been established in animal-derived foods. On the other hand, thiamphenicol (TAP) and florfenicol (FLP) are allowed but different MRLs have been set in foodstuffs of animal origin. In this work, precipitation polymerisation has been used and different MIP sorbents were tested and optimized for the solid-phase extraction (MISPE) of a group of three, structurally related amphenicols in milk powder. Recoveries were calculated using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) working in negative mode. The proposed confirmatory method was validated according to the Commission Decision 2002/657/EC, resulting in CCα ranging from 0.06 to 10.5 ng mL−1 and reaching the required working levels. The applicability of these polymers for the extraction of amphenicols in spiked samples of baby formulas has been tested.
A coprecipitation procedure for the determination of some metals in food and environmental samples by flame atomic absorption spectroscopy by Coşkun Özdemir; Şerife Saçmacı; Şenol Kartal (3977-3983).
A novel, rapid, and simple preconcentration procedure based on the coprecipitation of Cr(iii), Cu(ii), Fe(iii), Pb(ii), Pd(ii) and Zn(ii) ions with Ni(ii)–α-benzoin oxime precipitate was developed prior to flame atomic absorption spectrometric determination. The optimum values of the important analytical parameters influencing the quantitative coprecipitation of the analytes were as follows: pH 8.5, amount of α-benzoin oxime: 100 mg, amount of Ni(ii) as carrier element: 0.25 mg, time duration: 10 min. The effects of alkali (4000–15 000 mg L−1) and alkaline earth (1000–4000 mg L−1) metals on the recovery were also studied. The alkali metal ions (K+ up to 4000 and Na+ up to 15 000 mg L−1) and alkaline earth metal ions (Mg2+ up to 1000 and Ca2+ up to 4000 mg L−1) did not show any interference effect on the recovery of the analytes. Under the optimized conditions, the detection limits (3s, N = 10) for the analytes were in the range of 0.1–5.3 μg L−1. The accuracy of the presented coprecipitation method was checked by the analysis of certified reference materials. The method was applied to the determination of the analytes in real samples such as natural water and food samples, and good results were obtained (relative standard deviation <5%, recovery >95%).
Preparation of Fe3O4@TiO2/graphene oxide magnetic microspheres for microchip-based preconcentration of estrogens in milk and milk powder samples by Miaomiao Tian; Wei Feng; Juanjuan Ye; Qiong Jia (3984-3991).
We reported new magnetic microspheres as the adsorbent of estrogens. They were prepared by coating Fe3O4 particles with a composite made from titanium dioxide and graphene oxide (Fe3O4@TiO2/GO). The beads were loaded into a microfluidic chip and used to adsorb estrone (E1), estradiol (E2), and estriol (E3). The estrogens were then eluted from the beads with methanol and submitted to high performance liquid chromatography (HPLC) determination. Effects of sample volume, sample flow rate, sample pH value, and eluent flow rate were optimized. The limits of detection for estrogens were in the range of 4.3–7.5 ng mL−1, and recoveries ranged from 70.6% to 94.5%. Intra-day and inter-day relative standard deviations were less than 2.5% and 3.2%, respectively. The results indicated that the method was successfully applied to the determination of estrogens in milk and milk powder samples.
Fabrication of a CuS/graphene nanocomposite modified electrode and its application for electrochemical determination of esculetin by Xiaojuan Zhao; Fengyuan Zhang; Daban Lu; Yongling Du; Weichun Ye; Chunming Wang (3992-3998).
In this paper, a CuS/graphene nanocomposite modified glassy carbon electrode (GCE) was successfully constructed and used for determination of esculetin. The electrochemical behavior of esculetin was studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results indicated that the synergistic effect between CuS nanoparticles (NPs) and graphene enhanced the electrochemical response of esculetin. Under optimal conditions, the DPV peak current increased linearly with the esculetin concentration in the range from 1.0 × 10−7 to 1.0 × 10−4 mol L−1, and the detection limit (S/N = 3) was 5.8 × 10−8 mol L−1. Furthermore, a good selectivity with high sensitivity was obtained for the determination of esculetin in real samples.
Magnetic retrieval of an extractant: fast ultrasound-assisted emulsification liquid–liquid microextraction for the determination of polycyclic aromatic hydrocarbons in environmental water samples by Niya Wang; Rui Shen; Zhihong Yan; Hui Feng; Qingyun Cai; Shouzhuo Yao (3999-4004).
A novel two-step extraction technique combining ultrasound-assisted emulsification liquid–liquid microextraction with magnetic retrieval has been developed and applied to the analysis of six polycyclic aromatic hydrocarbons in environmental water samples coupled with high-performance liquid chromatography. The technique involves an initial extraction of the target analytes by ultrasound-assisted emulsification liquid–liquid microextraction into fine droplets of an organic extractant; and a retrieval and separation process of the organic phase from the aqueous solution with highly hydrophobic magnetic particles. In this way, the organic phase containing the analytes is the target of the magnetic retrieval step rather than the analytes directly. A noteworthy feature of the method is the introduction of highly hydrophobic magnetic particles with hierarchical structure for the magnetic retrieval of an extractant. Under the optimized conditions, good linearity ranging from 0.016 to 80 μg L−1 was obtained in spiked water samples with correlation coefficients (R2) ranging from 0.9962 to 0.9998 and low limits of detection ranging from 2.0 to 19.5 ng L−1. The proposed method has been validated in the analysis of real water samples with recoveries in the range of 75.4% to 110.5% and relative standard deviations of less than 9.9%.
Methylphosphonic acid as a 31P-NMR standard for the quantitative determination of phosphorus in carbonated beverages by Marek Kõllo; Marina Kudrjašova; Maria Kulp; Riina Aav (4005-4009).
Methylphosphonic acid (MPA) is introduced as an internal standard for the determination of the phosphorus content of carbonated beverages (cola drinks) by quantitative 31P-NMR analysis. Phosphorus in cola beverages was analyzed as phosphate in ten commercially available drinks. Phosphate concentration in the studied samples was in the range of 3.5 to 6.1 mM. The preparation of the samples included: degassing of commercially available beverages, addition of MPA as an internal standard, D2O for signal locking and a solution of NaOH to ensure a basic environment in the sample. The calibration graphs of the MPA standard and analyte showed a linear response in the concentration range of interest. The measured values of the phosphoric acid standard solutions lay within the confidence limits of the MPA, showing that these compounds give a similar response in NMR analysis. The measured concentrations of phosphorus were in good agreement with the values detected by the traditional spectrophotometric method. The presented 31P-NMR method using MPA as an internal standard is reliable and simple for the determination of the phosphorus content of cola type beverages.
Long-range memory patterns in variations of environmental radon in soil by Ermioni Petraki; Dimitrios Nikolopoulos; Anaxagoras Fotopoulos; Dionisios Panagiotaras; Constantinos Nomicos; Panayiotis Yannakopoulos; Sofia Kottou; Athanasios Zisos; Anna Louizi; John Stonham (4010-4020).
This paper addresses issues of long-range memory and self-organisation in variations of radon in soil in Greece. The methods of rescaled-range, roughness-length, variogram, fractal dimension and block entropy were employed through lumping. Sliding was utilised with the wavelet spectral fractal technique. Antipersistent Hurst exponents in the range 0 < H < 0.5 were mainly identified. Persistent exponents (0.5 < H < 1) were also detected. Switching between persistency and antipersistency was observed and considered consistent with an underlying geo-environmental long-memory self-organisation. Fractal dimensions were in the range 1.2 < D < 2. The anomalous parts of the 2008 radon signal presented significantly lower fractal dimensions. Value ranges of Shannon, Shannon-per-letter, conditional, Tsallis and normalised Tsallis block entropies were 0.67 ≤H(n) ≤ 2.73, 0.2 ≤h(n)≤ 0.7, 0.2 ≤h(n)≤ 0.6, 0.36 ≤Sq≤ 1.11, 0.50 ≤Ŝq≤ 9.55 respectively. The entropy values were affected by the block-size n. The entropic index values of the radon anomalies were significantly lower indicating long-memory underlying patterns. Underlying sources are discussed. The asperity-model is proposed.
Determination of Brilliant Blue FCF in food and cosmetic samples by ionic liquid independent disperse liquid–liquid micro-extraction by Jingbo Guo; Hao Wu; Liming Du; Yunlong Fu (4021-4026).
A novel, relatively fast and simple method of ionic liquid independent disperse liquid–liquid micro-extraction (IL-IDLLME) coupled with UV-Visible spectroscopy was developed and applied to determination of the synthetic dye Brilliant Blue FCF (E133) in six different kinds of food and cosmetic samples, namely soft drinks, candy, jelly, kiwi fruit (Actinidia chinensis) pieces, roasted pea, ice cream, eau de toilette and shampoo. The samples were dissolved in water and preconcentrated simply by using 1-decyl-3-methylimidazolium tetrafluoroborate ([C10MIM][BF4]) without a dispersive solvent, heat, ultrasonication or additional chemical reagents. The effects of different parameters such as the volume of [C10MIM][BF4], pH, KCl concentration, micro-extraction temperature, incubation time and centrifugation time on the micro-extraction of E133 (0.12 μg mL−1) were investigated and optimum conditions were established. A linear calibration curve was obtained in the range of 1.5–150 μg L−1 for E133 under optimum conditions. The limit of detection (LOD) based on 3Sb was 0.34 μg L−1 (n = 11). The relative standard deviation (R.S.D.) for 5 and 140 μg L−1 of E133 was 0.43% and 0.82% (n = 10), respectively. The method is therefore recommended for use by the quality control departments of food and cosmetic producers using E133.
Combined microporous membrane-based liquid–liquid–liquid microextraction and in situ differential pulse voltammetry for highly sensitive detection of trimipramine by Ali A. Ensafi; Sedigheh Rabiei; Behzad Rezaei; Mehdi Jafari-Asl (4027-4033).
In this paper, a microporous membrane-based liquid–liquid–liquid microextraction and electrochemical analysis are used to purify, preconcentrate and detect ultra-trace amounts of trimipramine in biological fluids such as plasma and urine. For the microextraction of trimipramine, a porous polyethylene membrane was saturated with isoamyl benzoate. A phosphoric acid solution and an alkaline solution were used as the acceptor and source phase, respectively. The influence of effective parameters on both extraction efficiency and peak current of trimipramine on a multiwall carbon nanotube-modified carbon paste electrode was studied. The best results were obtained in a sample solution of 0.06 mol L−1 NaOH and an acceptor phase of 0.06 mol L−1 phosphoric acid at a rotation rate of 1200 rpm and a temperature of 65 °C over an extraction time of 20 min. The analyte was extracted from the source phase quantitatively with an enrichment factor of 16.3. Because of the memory effect, a new membrane was used for each extraction. The detection limit was 2.0 nmol L−1 trimipramine with an RSD of 4.3%. The method was found to be highly selective and sensitive for detecting trimipramine in biological fluids.
Simultaneous determination of aconitine, mesaconitine, hypaconitine, bulleyaconitine and lappaconitine in human urine by liquid chromatography-electrospray ionization-tandem mass spectrometry by Mei Li; Zongwei Cai (4034-4038).
Aconitine, hypaconitine, mesaconitine, bulleyaconitine and lappaconitine are Aconitum alkaloids that have been proved to be neurotoxic and cardiotoxic. A method with liquid–liquid extraction and liquid chromatography coupled with electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) was developed and validated for the quantification of the five Aconitum alkaloids in human urine. Upon the successful chromatographic separation, the alkaloids were determined by ion trap tandem mass spectrometry. The precursor and major product ions of aconitine at m/z 646 → 586, mesaconitine at m/z 632 → 572, hypaconitine at m/z 616 → 556, bulleyaconitine at m/z 644 → 586 and lappaconitine at m/z 585 → 535 were monitored in positive ion mode. Linear calibration curves were generated from 0.02–5 μg mL−1 with coefficients of greater than 0.99. The method was validated with the intra-day and inter-day precisions represented by relative standard deviation of less than 7% in urine, and the recoveries from spiked urine samples varied from 89.8% to 96.4% for lappaconitine, 87.4–96.3% for hypaconitine, 81.5–90.6% for mesaconitine, 82.6–90.0% for aconitine and 82.2–88.7% for aconitine. Stability of aconitine was assessed under acidic, neutral and alkaline conditions. Aconitine hydrolysis was not observed during the urine sample pretreatment under neutral and weak acidic conditions.
Multivariate calibration to implement green ETAAS methods when analysing Cu in lubricating oils by J. M. Andrade; S. Carballo-Paradelo; J. Terán-Baamonde; A. Carlosena; R. M. Soto-Ferreiro; D. Prada-Rodríguez (4039-4046).
The quantification of metals in lubricating oils is relevant to trace machinery wearing and to evaluate potential environmental effects related to their disposal. Electrothermal atomic absorption spectrometry (ETAAS) is a common choice to measure metal content and despite efforts being made to reduce the amount of organic materials in the measurement aliquot (e.g., using emulsions), potential interferents still remain there. Therefore, quantification of the analyte is a highly difficult task. In this work a general-purpose methodology based on multivariate partial least squares regression (PLS) is presented to address interferences when difficult organic materials are analysed by ETAAS. It is shown that such a methodology yields powerful quantification models and requires less staff dedication, shorter turnaround times and lower expenses than traditional approaches. Besides, it is totally compatible with green analytical chemistry principles. Further, figures of merit which consider the risk of false negatives and false positives were calculated following the latest ISO and European guidelines: critical level (decision limit), minimum detectable value (detection capability), trueness and precision, multivariate sensitivity and sample-specific confidence interval. They have not been used in the atomic spectrometry field. The case study is about quantifying Cu in lubricating oils as a tracer of machine weathering.
Optimisation of asymmetrical flow-field fractionation for the characterisation of gum arabic (Acacia sengal var senegal) and comparison with gel permeation chromatography by Marina Andres-Brull; Saphwan Al-Assaf; Glyn O. Phillips; Kevin Jackson (4047-4052).
Asymmetrical flow field-flow fractionation (AF4) linked to three detection systems (multi angle laser light scattering, refractive index and UV) was used to determine the molecular weight and molecular distribution of the component Acacia sengal var senegal (henceforth referred to as gum arabic). The effects of sample concentration and applied field strength (cross-flow) were examined to determine the optimum fractionation conditions in comparison with the behaviour of a monodispersed polysaccharide (Pullulan-100). The results using AF4-MALLS are in good agreement with those using GPC-MALLS.
Selenium speciation by liquid chromatography-particle beam/mass spectrometry (LC-PB/MS): application to a yeast reference material and synthetic urine by Joaudimir Castro; M. V. Balarama Krishna; Geovannie Ojeda; R. Kenneth Marcus (4053-4059).
Presented here is the comprehensive speciation of organic and inorganic selenium species via liquid chromatography-particle beam/electron impact mass spectrometry (LC-PB/EIMS). Two different matrices (SELM-1 selenium-enriched yeast certified reference material and synthetic urine) were analyzed for the content of methionine and selenium species utilizing this analytical tool. An ion-paring reversed-phase chromatographic separation using a linear gradient of water and methanol (each containing 0.1% trifluoroacetic acid), at 0.9 mL min−1 with an analysis time of less than 20 minute, was employed for the selenium speciation. Electron ionization mass spectra yielded clear and simple fragmentation patterns of the chemical species eluting from the chromatographic column. Quantification by a standard addition method was accomplished for methionine (m/z = 149 Da) and selenomethionine (m/z = 196 Da) with recoveries of 93% (9% RSD, n = 4) and 97% (11% RSD, n = 4), respectively. Absolute limits of detection on the nanogram level were obtained for each of the targeted species.
Multivariate analysis of pyrolysis-GC/MS data for identification of polysaccharide binding media by Chiara Riedo; Dominique Scalarone; Oscar Chiantore (4060-4067).
The method of Thermally assisted Hydrolysis and Methylation (THM) was applied to the analysis of plant gums that can be found in artistic and archaeological objects. The main products obtained by THM of gums arabic, cherry, tragacanth, ghatti and karaya are permethylated and partially methylated 3-deoxyaldonic acids, characteristic products obtained from alkaline hydrolysis of monosaccharides. These markers allowed only a preliminary distinction between the different gums because they are not representative of the entire monosaccharides profile. As classification on the basis of sugars quantification is impossible, multivariate data analysis was employed, using the peak areas of THM products as variables. Calculations were performed on several different sets of data, enhancing the capability of the method to differentiate gums, also when submitted to accelerated ageing treatments. A case study on samples coming from ancient Egyptian cartonnage funerary masks is presented.
A direct competitive inhibition time-resolved fluoroimmunoassay for the detection of unconjugated estriol in serum of pregnant women by Yong-ping Tang; Su-qing Zhao; Ying-song Wu; Jian-wei Zhou; Ming Li (4068-4073).
Unconjugated estriol (uE3) is one of the most important serum markers for prenatal screening. The abnormally low content of uE3 is used as an indicator of fetal DS (Down syndrome) during the second trimester in pregnant women. In the present study, we developed a time-resolved fluoroimmunoassay to detect uE3 by employing microtiter plates with pre-captured primary antibodies. E3-3-CME-BSA (estriol-3-carboxymethyl ether-bovine serum albumin) conjugates served as labels and Eu3+ (europium) as the probe for signal detection. The detection limit of this assay was 0.35 nmol L−1. The within-run and between-run imprecision values for serum control detection were less than 5.0% and 6.0% respectively. The mean recovery was 102.6%. The long-term stability (2–8 °C, 15 months) and thermostability (37 °C, 10 days) were excellent. The uE3 concentrations measured by the present assay in 1168 Chinese maternal serum samples correlated well with those obtained by the chemiluminescence immunoassay assay (r = 0.948). The reference range in normal singleton pregnancies in Southern China was established which provided reference data to adjust the uE3 medians for biochemical screening.
Multivariate data analysis of impedimetric biosensor responses from Salmonella typhimurium by Giyoung Kim; Ji-Hea Moon; Mark Morgan (4074-4080).
A multivariate data analysis was performed on responses of an impedimetric biosensor to quantify Salmonella typhimurium. To develop the impedimetric biosensor, an interdigitated microelectrode (IME) was fabricated by using a semiconductor fabrication process. Anti-Salmonella antibodies were immobilized based on streptavidin–biotin binding on the surface of the IME to form an active sensing layer. The impedance spectra of the biosensor were measured at frequencies ranging between 10 Hz and 1 MHz with different concentrations of S. typhimurium in PBS and pork samples. Partial-least squares (PLS) regression models were developed and evaluated as a multivariate data analysis method. The best PLS regression model developed from impedance spectra that were acquired with different individual biosensors had the correlation coefficient of determination (R2) 0.75 and 0.59 for PBS and pork samples, respectively. The PLS models estimated the concentration of S. typhimurium with 1.49 and 1.96 Log CFU mL−1 of root mean square of error in prediction (RMSEP) for PBS and pork samples, respectively. The PLS model built with impedance data from the same biosensor improved R2 to 0.85 and 0.89, and reduced the RMSEPs to 1.13 and 1.02 Log CFU mL−1 for PBS and pork samples, respectively. This study showed the feasibility of quantifying S. typhimurium by performing multivariate analysis on responses from the impedimetric biosensor.
Potential barrier modulation in ZnO nanostructures and their CO sensing properties by Prabhakar Rai; Yeon Tae Yu (4081-4087).
Colloidal ZnO nanostructures were synthesized by using a high-temperature solution-phase hydrolysis approach. ZnO nanoparticles (NPs) with ∼25 nm particle size were synthesized in ethylene glycol (EG), whereas ZnO nanospheres with an average diameter of ∼500 nm (composed of 10–15 nm ZnO NPs) were formed in polyethylene glycol (PEG). The effect of solvents on the morphology of ZnO nanocrystal clusters was investigated. UV-visible absorption band of both samples was blue-shifted as compared to bulk ZnO. ZnO NPs showed strong UV emission and weak green emission, whereas ZnO nanospheres displayed strong green emission, along with UV emission, in the photoluminescence (PL) spectrum. As prepared ZnO nanostructures were applied for CO sensing, where ZnO NPs exhibited higher response than ZnO nanospheres, although the grain size of ZnO NPs was almost double that of ZnO nanospheres. A relationship between sensing layer microstructure and inter-electrode gap was established. It was demonstrated that the arrangement of grains in the sensing layer between the electrodes plays an important role in gas sensing.
Preparation and chemical characterisation of an Asian mineral dust certified reference material by Masataka Nishikawa; Dashdondog Batdorj; Miyuki Ukachi; Kaoru Onishi; Kimiyo Nagano; Ikuko Mori; Ichiro Matsui; Tomoharu Sano (4088-4095).
Surface soil was collected from 4 locations in the southern Gobi Desert in Mongolia and the pooled material was subjected to coarse sieving, cyclone classification, refinement and homogenisation, yielding 1.2 kg of a fine dust of particle diameter below 10 μm. For certification, elemental analyses were performed by thirteen independent laboratories and, after statistical assessment of the data, 11 elements, Na, Mg, Al, K, Ca, Ti, Fe, Mn, Zn, Sr and Ba, were certified. A further 11 elements, Si, P, Sc, Cr, Co, Ni, Cu, La, Pb, Th and U, were given reference-only values. This certified reference material (CRM) has been designated NIES no. 30 “Gobi Kosa Dust”. We estimate the aerodynamic diameter (median diameter) of the dust to be about 4 μm, which is within the range of median diameters (3–5 μm) of Asian mineral dust (termed kosa in Japanese) that is wind-borne to Japan. The mineral composition of the dust based on the ratio of elemental concentration to Al concentration is very similar to those for eleven kosa dust samples collected in Japan. This new CRM also contains clay minerals and calcite that are characteristic of kosa dust. Carbonate carbon, derived from calcite, was estimated to account for about 50% of the total carbon content (2.16%) of the material. The amount of calcium extracted by 5% acetic acid solution represented about 90% of the total Ca content of the CRM. Assuming that Ca was all in the form of calcium carbonate, the carbonate carbon content was calculated to be 1.1%; this value being in good agreement with direct analysis. NIES no. 30 is considered to be a useful material for quality control purposes as well as for verification of experiments concerned with environmental behaviour of Asian mineral dust.
Assessment of a sequential extraction procedure for arsenic partitioning and application to samples from different pollution sources by Raquel Larios; Rodolfo Fernández-Martínez; Isabel Rucandio (4096-4104).
In this paper, a seven-step sequential extraction procedure (SEP) is proposed to evaluate As fractionation in environmental solid samples of concern. The protocol covers the most relevant As-bearing phases in soils and sediments, stressing the importance of the most mobilizable fractions, in accordance with their potential environmental hazards. The considered fractions are (1) readily soluble As, (2) strongly adsorbed As onto mineral surfaces, (3) As associated with Al oxyhydroxides, (4) As bound to organic matter, (5) As incorporated into amorphous Fe oxyhydroxides, (6) As associated with poorly crystalline Fe (hydr)oxides and (7) As coprecipitated with refractory minerals. Although this protocol is suitable for all kinds of environmental solid samples, it was especially designed for those that are highly polluted. Hence, optimization of some operational parameters in every extraction step such as the extraction time and solid-to-solution ratio was carried out by using highly polluted solids as control samples. The selectivity of the selected agents for every extraction step was assured through experiments with natural and synthetic matrices of As-bearing minerals and As-spiked materials. The validation of the proposed method was accomplished with five certified materials of soils and sediments covering a diverse range of As contents. The results of its application to As-contaminated samples from different geological origins and within a wide range of As contents revealed As fractionation to be largely in accordance with the pollution source of samples and with their geochemical composition, which confirmed this methodology to be suitable for fractionation assessment of As in environmental solid samples of different nature. In addition, one of the strengths of this method is that the simplicity of its steps would easily allow for its automation.
Frontal elution paper chromatography for ambient ionization mass spectrometry: analyzing powder samples by Yun-Qing Huang; Jin-Qing You; Yupeng Cheng; Wenjian Sun; Li Ding; Yu-Qi Feng (4105-4111).
We developed a convenient method by coupling frontal elution paper chromatography with desorption corona beam ionization mass spectrometry (FEPC/DCBI-MS) for rapid analysis of powder samples. In this method, the powder was deposited directly onto a coarse strip near the base of a triangular paper sheet, and then a strong elution solvent was pipetted onto the base of the paper sheet in the open air for developing. The sample zone migrated at the solvent front under strong elution conditions. Target analytes were finally condensed at the V-shaped tip which was then placed under the visible plasma beam of DCBI for ionization. Steps of solvent extraction and developing were performed on a paper sheet simultaneously. The overall procedure requires less than two minutes. Signal intensities of target analytes were improved significantly due to analyte condensation at the tip and matrix effect reduction. Fundamentals and applications of FEPC/DCBI-MS were demonstrated by analysis of chlorphenamine in herbal medicines, clenbuterol in pig feed powder and nicotine in house-hold dust. The limits of detection ranged from 0.35 μg g−1 to 1.5 μg g−1 (0.52–2.2 ng, absolute) in full-scan positive-ion mode. The linear range was 5.0 μg g−1 to 5.0 × 102μg g−1 with satisfactory linear coefficient (R2 = 0.885–0.956). Good reproducibility was achieved with relative standard deviations (RSDs) less than 20% and the recoveries ranged from 70 to 90%. The results demonstrate that the improved FEPC-DCBI-MS method is satisfactory for semi-quantitative evaluation of analytes in powder samples.
A practical and rapid method for the simultaneous isolation, purification and quantification of geniposide from the fruit of Gardenia jasminoides Ellis by MSPD extraction and UFLC analysis by Yan Gao; Ying Sun; Yuanpeng Wang; Jia Zhang; Bo Xu; Hanqi Zhang; Daqian Song (4112-4118).
A practical, simple and rapid method based on matrix solid phase dispersion (MSPD) extraction and ultrafast liquid chromatography (UFLC) was developed and validated for the simultaneous isolation, purification and quantification of geniposide from the fruit of Gardenia jasminoides Ellis. The experimental parameters such as the type of dispersing sorbent and elution solvent, the volume of elution solvent, the ratio of sorbent/sample and the particle size of sample were first studied separately by a univariate method. Then relevant parameters were evaluated by orthogonal screening to determine the optimal operation conditions. The optimal conditions were 0.5 g of fruit of Gardenia jasminoides Ellis, 0.75 g of Celite (diatomaceous earth) as dispersing sorbent and a volume of 25 mL of aqueous solutions containing 70% methanol as the elution solvent. The feasibility of the method was evaluated by investigating linearity, accuracy, precision, real sample analysis, limit of detection (LOD) and limit of quantification (LOQ). The LOD and LOQ were 0.026 and 0.087 μg mL−1, respectively. The recoveries ranged from 87.9% to 104.8% at two spiking levels with relative deviations (RSDs) ranging from 0.6% to 3.9%. Compared with the conventional extraction methods, such as ultrasound-assisted extraction (UAE) and Soxhlet extraction (SE), the proposed method is quicker and more effective.
Simultaneous determination of ascorbic acid and acetaminophen at the pre-anodized inlaying ultrathin carbon paste electrode by Jianling Wang; Jing'e Huo; Jing Li; Enbo Shangguan; Quanmin Li (4119-4125).
A pre-anodized inlaying ultrathin carbon paste electrode (PAIUCPE) was constructed using simple and fast electrochemical pretreatment for the simultaneous determination of ascorbic acid (AA) and acetaminophen (ACOP). The effect of pH on peak current and peak potential for the oxidation of AA and ACOP was discussed in detail. The results showed that the size of ip of AA and ACOP was closely related to the degree of oxygen reduction reaction at the auxiliary electrode. In pH 5.00 phosphate buffer solution, a linear relationship between oxidation peak current and concentration of AA and ACOP was obtained in the range of 1.0 × 10−5 to 1.5 × 10−3 mol L−1 and 3.0 × 10−7 to 2.0 × 10−4 mol L−1, and the detection limits were estimated to be 3.10 × 10−7 mol L−1 and 2.28 × 10−8 mol L−1, respectively. The constructed electrode exhibited excellent reproducibility and stability. Moreover, this method was employed to determine AA and ACOP in Vitamin C Yinqiao Tablets with satisfactory results.
Liquid crystal based sensors for the detection of cholic acid by Sihui He; Wenlang Liang; Colleen Tanner; Kung-Lung Cheng; Jiyu Fang; Shin-Tson Wu (4126-4130).
The concentration level of cholic acid is a biomarker for the early diagnosis of liver and intestinal diseases. We present a biosensor platform based on the anchoring transition of 4-cyano-4′-pentylbiphenyl (5CB) liquid crystals at surfactant-laden 5CB/aqueous interfaces for the detection of cholic acid (CA) in aqueous solution. In the biosensor platform, the competitive adsorption of CA at the surfactant-laden 5CB/aqueous interfaces can trigger a homeotropic-to-planar anchoring transition of the 5CB at the interface, which can be easily observed using a polarizing optical microscope. We find that the detection limit of the 5CB based biosensors for CA depends on the pH and ionic strength of the aqueous phase and the headgroup of the surfactants.
A simplified method for determination of organic mercury in soils by Rodolfo Fernández-Martínez; Isabel Rucandio (4131-4137).
Monitoring levels of organic mercury species at very low concentrations in the environment is of concern due to their high toxicity. However, conventional methods for organic mercury determination are usually expensive and time consuming because they involve many preparation steps and require instrumentation which is not available in most laboratories. In order to make it easier the organic mercury determination this paper presents a simple, fast and reliable extraction method for isolating and quantifying the organic mercury fraction in soil samples. The proposed method is based on one single digestion stage using a CuBr2 solution in HCl to release the organic mercury compounds from the solid matrix and their simultaneous and selective extraction into dichloromethane. After the separation of the organic phase, reextraction into aqueous media using N-acetyl-l-cysteine solution allows the determination of the extracted organic mercury by electrothermal atomic absorption spectrometry with the direct mercury analyzer DMA-80. Experimental and instrumental variables were optimized by the analysis of synthetic samples of methylmercury dispersed in pulverized silica. The method was validated by the analysis of the certified CRM 580 reference material. The detection limit of the procedure is 9.6 ng of organic mercury per gram of dry soil. The applicability of the proposed method to real samples was demonstrated through recovery studies of methylmercury in spiked soils. In addition, the influence of the TOC (Total Organic Carbon) content in soils was studied. The recoveries obtained under optimal experimental conditions ranged from 90% to 105% for all tested samples, indicating the suitability of the proposed method for determination of the organic mercury fraction in soils.
Development of narrow-band TLC plates for TLC/FTIR analysis by Fang Wang; Haijun Wu; Qing Zhu; Kun Huang; Yongju Wei; Cuige Liu; Yanjun Zhai; Zhanlan Yang; Shifu Weng; Yizhuang Xu; Isao Noda; Jinguang Wu (4138-4144).
The present paper focuses on the development of narrow-band thin-layer chromatography (TLC) coupled with Fourier transform Infrared spectroscopy (FTIR) technique. We adopted a new method to prepare a narrow-band TLC plate by using silver iodide as stationary phase. The narrow-band TLC plate exhibits a variety of advantages: the preparation time is about 20 minutes, while 3–7 days are needed to prepare a common TLC plate suitable for TLC/FTIR analysis by using “settlement volatilization method”. Furthermore, the usage of stationary phase in narrow-band TLC plates decreases by about one order of magnitude in comparison with that of common TLC plates. This is very important for an expensive stationary phase such as silver iodide. In addition, experimental results of TLC/FTIR analysis on mixed samples containing rhodamine B and bromocresol green demonstrate the detection limit significantly improves by using the narrow-band TLC technique.
Simple and direct potentiometric determination of potassium ions in biodiesel microemulsions at a glassy carbon electrode modified with nickel(ii) hexacyanoferrate nanoparticles by Graziela Cristina Sedenho; Leonardo Lataro Paim; Nelson Ramos Stradiotto (4145-4151).
Considering the great importance of the determination of inorganic ions present in fuels, particularly in relation to potassium, the scope of this work was to develop a potentiometric method using a chemically modified electrode with nanoparticles of nickel hexacyanoferrate for the determination of potassium ions in a microemulsion of biodiesel. The electrochemical studies showed the possibility of electrochemical measurements in biodiesel microemulsion and the good stability of the modified electrode in this medium. The modified electrodes (surface excess of 16.1 ± 1.6 nmol cm−2) in a microemulsion composed of biodiesel : propan-1-ol : aqueous phase (5 : 70 : 25 in volume) exhibited a detection limit for potassium ions of 5.3 × 10−5 mol L−1 and a slope of 58 mV, with a linear response in the concentration range of 5.0 × 10−5 mol L−1 to 1.0 × 10−2 mol L−1. The recoveries obtained were between 91 and 106%. Thus, the proposed method using the preparation of a microemulsion of the samples proved to be an efficient method for the determination of potassium in biodiesel.
Raman based detection of Staphylococcus aureus utilizing single domain antibody coated nanoparticle labels and magnetic trapping by Philip Drake; Pei-Shin Jiang; Hong-Wen Chang; Siou-Cing Su; Jamshid Tanha; Li-Lin Tay; Peilin Chen; Yuh-Jiuan Lin (4152-4158).
Nanoparticle labels were used to detect the pathogenic bacteria Staphylococcus aureus. Two different labels were employed. These consisted of nanoparticles based on iron-oxide for magnetic trapping and isolation of the bacteria and surface enhanced Raman spectroscopy (SERS) active gold nanoparticles (AuNPs) coated with 4-mercaptobenzoic acid for the detection and quantification of the bacteria. Both types of nanoparticles were conjugated with single domain antibodies that selectively bind to protein A on the surface of S. aureus. Transmission electron microscopy (TEM) image analysis showed the iron-oxide nanoparticles to have magnetic core diameters of 20 nm ± 3 nm and the gold nanoparticles to be 51 nm ± 2 nm in diameter. A response curve was obtained displaying a logarithmic dependency between the 1073 cm−1 peak intensity in the SERS spectra of the AuNPs and the concentration of S. aureus cells in the initial sample. The overall detection limit was estimated to be 1 S. aureus cell mL−1 in less than 10 min without culturing.
Label-free electrochemical immunosensors for the detection of zeranol using graphene sheets and nickel hexacyanoferrate nanocomposites by Xiaodong Xue; Dong Wei; Rui Feng; Huan Wang; Qin Wei; Bin Du (4159-4164).
In this study, a novel label-free electrochemical immunosensor has been developed by immobilizing graphene sheets (GS) and nickel hexacyanoferrate nanocomposites (NiNPs) for the detection of zeranol (ZER). NiNPs were used as electron transfer mediators, and electroactivity was greatly enhanced in the presence of GS, which was ascribed to the good electron-transfer ability of GS. The modification procedure was characterized by cyclic voltammetry (CV). The detection is based on the current change of the modified electrode before and after the antigen–antibody reaction. Under optimum conditions, the detection of ZER demonstrated that the immunosensor exhibited a wide linear range of 0.05–10.0 ng mL−1 with a low detection limit of 6 pg mL−1. The proposed immunosensor also showed good performances such as high sensitivity, good selectivity and stability. The reliability of the developed immunosensor has been proved by the detection of ZER in river water samples with satisfactory results.
A glucose biosensor based on cytochrome c and glucose oxidase co-entrapped in chitosan–gold nanoparticles modified electrode by Yonghai Song; Hongyu Liu; Yu Wang; Li Wang (4165-4171).
A glucose biosensor was developed based on cytochrome c (Cyt c) and glucose oxidase (GOD) co-entrapped on gold nanoparticles (AuNPs)–chitosan (CHIT) nanocomposites which were constructed on glassy carbon electrode (GCE) by one-step electrodeposition. The surrounding Cyt c around GOD provided a biocompatible microenvironment to keep GOD's biological activity. Simultaneously, the AuNPs–CHIT nanocomposites provided a roughened surface with large surface-to-volume ratio to greatly amplify the surface coverage of GOD–Cyt c molecules and good conductivity to realize the direct electron transfer (DET) of GOD. The biosensor showed a wide detection range, low detection limit, good stability and high sensitivity. Thus, this study not only successfully achieved DET of GOD, but also constructed satisfactory point-of-care glucose monitoring.
Effectiveness of different cleanup sorbents for the determination of avermectins in fish by liquid chromatography tandem mass spectrometry by I. Rafidah; S. Ghanthimathi; A. B. Fatimah; N. A. Mahyudin (4172-4178).
An effectiveness and comparative study of cleanup sorbents used in dispersive solid phase extraction (DSPE) for the determination of avermectins, including emamectin (EMA), abamectin (ABA), doramectin (DOR), moxidectin (MOX), and ivermectin (IVE), was performed. Three different types of cleanup sorbents, alumina (Al), primary and secondary amine (PSA) and octadecyl (C18), were used to remove the matrix interference in fish samples. Homogenised fish samples were extracted with acetonitrile, magnesium sulphate anhydrous and sodium chloride. The cleanup sorbents were separately applied to the supernatant during the DSPE procedure; the mixtures were shaken and centrifuged, and the supernatant was dried. The extracts were reconstituted with acetonitrile/water and quantified by liquid chromatography tandem mass spectrometry with electrospray ionisation in the positive mode with two product ions that were monitored by selected reaction monitoring. The performance of each cleanup sorbent was observed for its accuracy and precision in a spiked blank sample at a concentration of 5 μg kg−1. The combination of the cleanup sorbents PSA and C18 was found to be the most effective in the cleanup of the fish samples. In the validation tests, the detection limit was in the range of 0.3 μg kg−1 to 0.4 μg kg−1, and the quantitation limit for all avermectins was 1 μg kg−1 in the linearity range of 1–15 μg kg−1. The recoveries of avermectins were 91.9–102.5%, with a relative standard deviation lower than 19%.
Heterocyclic thiosemicarbazones as fluorescent sensors for the selective recognition of cations in the aqueous phase by Sivalingam Suganya; Duraisamy Udhayakumari; Sivan Velmathi (4179-4183).
Highly sensitive and selective fluorescent cation sensors 1–3, based on heterocyclic derivatives, have been synthesized from the condensation reaction between their corresponding heterocyclic aldehydes and thiosemicarbazide. All of the receptors 1–3 can act as optical sensors for the detection of Cu2+ and Hg2+ ions, and as fluorescent sensors for the Cr3+ ion, via a chelation enhanced fluorescence effect in an aqueous environment. The structures of the receptors 1–3 were well characterized by IR, 1H NMR, 13C NMR and HRMS techniques and their cation sensing abilities were studied by UV-vis and fluorescence spectroscopy.
Non-invasive differentiation between natural and synthetic ultramarine blue pigments by means of 250–900 nm FORS analysis by Maurizio Aceto; Angelo Agostino; Gaia Fenoglio; Marcello Picollo (4184-4189).
A totally non-invasive procedure has been developed for differentiation of natural and synthetic ultramarine blue pigments on the basis of collection of UV-visible spectra in diffuse reflectance mode, followed by a chemometric treatment of the data using unsupervised pattern recognition methods. The main spectral features of natural and synthetic paint samples, i.e. reflection maxima, inflection points and reflection minima, could not be useful enough in the differentiation process; a threshold of 455 nm in the comparison of reflectance maxima has been observed, with synthetic samples peaking lower than this value and natural samples peaking higher, but it was not considered efficient in the differentiation, according to the fact that reflection maxima could be subjected to a bathochromic shift as a consequence of the addition of white pigments to blue paints. Chemometric analysis was therefore used in order to exploit information contained in the whole spectrum. To obtain an efficient classification, a proper data transformation was performed on the spectral data, using Z-score standardised variables. Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) were the unsupervised pattern recognition methods used on the spectral data. Chemometric treatment was firstly applied to analysis of standard ultramarine blue paints and powder pigments and showed a good differentiation power, making it possible to distinguish between paints and raw lapis lazuli items and, more interestingly, between natural and synthetic ultramarine blue paints. Afterwards, PCA and HCA were applied to the analysis of blue paints on miniature painting artworks, again succeeding in the differentiation. This procedure could be used to develop a simple and totally non-invasive method for authenticating painted artworks.
Determination of artemisinin in Artemisia species by hollow fiber-based liquid-phase microextraction and electrospray ionization-ion mobility spectrometry by Mohammad Saraji; Taghi Khayamian; Zahra Hashemian; Shabnam Najafi Aslipashaki; Majid Talebi (4190-4195).
A method based on hollow fiber liquid-phase microextraction (HF-LPME) combined with electrospray ionization-ion mobility spectrometry was developed for the determination of artemisinin in the leaf, stem and root of six Artemisia species. Artemisinin was extracted from an aqueous sample through a thin phase of organic solvent (n-dodecane) filling the pores of the hollow fiber wall and then back extracted into the methanol located in the lumen of the hollow fiber. The effect of experimental parameters on the extraction efficiency of HF-LPME including sample ionic strength, stirring rate and extraction time were investigated. Under the optimized conditions, the linear dynamic range for the analyte was found to be 50–1000 ng mL−1 for the leaf and stem, and 20–500 ng mL−1 for the root of Artemisia vulgaris L. Detection limits were 24, 12 and 20 ng mL−1 (0.72, 0.36 and 0.61 mg kg−1 of dried sample) for the leaf, root and stem, respectively. The relative standard deviations for three replicate measurements of the method varied from 5.8% to 10.2% at a concentration level of 50–200 ng mL−1.
Accurate determination of pesticide residues incurred in tea by gas chromatography-high resolution isotope dilution mass spectrometry by Jie Feng; Hua Tang; Dazhou Chen; Haifeng Dong; Lei Li (4196-4204).
This paper presents the development of a precise and accurate analytical method for the determination of 12 incurred pesticides in tea using gas chromatography-high resolution isotope dilution mass spectrometry. The extraction efficiency of accelerated solvent extraction (ASE) was evaluated in which four extraction parameters, solvent, temperature, number of static cycles and static time for spiked and incurred samples, have been investigated systematically. The optimized solvent and temperature were found to be an acetone–n-hexane mixture (2 : 1, v/v) and 120 °C for both spiked and incurred samples. However, it was found that the number of static cycles and static time for the spiked tea sample were different from that for the incurred sample. Two cycles of 5 min each were set for the extraction of pesticides from the spiked tea, while two cycles of 10 min each were set for extraction from the incurred sample. The overall average recoveries using this method at three spiked concentration levels (50, 200, 1000 ng g−1) ranged from 95.96% to 102.04%, and relative standard deviations (RSDs) were in the range 0.83–3.12% (n = 6) for all analytes. The limits of detection (LODs) ranged from 0.02 to 10.83 ng g−1, and the limits of quantification (LOQs) ranged from 0.09 to 38.74 ng g−1. The RSDs (n = 6) of two incurred tea samples were in the range 1.04–2.93%, and 1.01–2.96%, respectively, which are better than those obtained using a QuEChERS-GC/MS/MS method. This indicates that the developed method is more suitable for the precise determination and research of pesticides incurred in tea.
Statistical methods and library search approaches for fast and reliable identification of dyes using surface-enhanced Raman spectroscopy (SERS) by Federica Pozzi; Simone Porcinai; John R. Lombardi; Marco Leona (4205-4212).
The identification of organic colorants is of high importance in the cultural heritage field, where they are found as paint components and textile dyes, and in forensic science, because of their use in inks and paints, food colorants and textile dyes. Surface-enhanced Raman spectroscopy (SERS) has emerged as a promising technique for the detection of these materials, yet concerns over the sensitivity of SERS spectra of dyes to chemical and instrumental variables (such as pH, choice of SERS substrates and/or aggregants, and excitation wavelength) have prevented its widespread use in analytical applications. Over the last few years, the development of several microanalytical approaches has considerably increased the chances of success in the identification of minute amounts of dyes by SERS. However, the need for searchable databases is still largely to be fulfilled. In this work, we have assembled the core of a comprehensive library which contains 100 Raman and SERS reference spectra of natural and synthetic organic colorants. Experiments to classify 20 query SERS spectra of dyes from a variety of museum objects were conducted using principal component analysis (PCA) and the correlation coefficient (CC) algorithm. The effect of spectral transformations such as baseline correction, selecting a standard frequency range, normalization, smoothing, as well as carrying out the search on the second derivative of the spectra, was systematically evaluated. With this study we demonstrate that SERS spectra of organic colorants can be reliably matched against a well constructed spectral library regardless of the instrumentation and the colloids used, and of the pH conditions at which the measurements were carried out.
Ultrasound-assisted liquid–liquid microextraction based on an ionic liquid for preconcentration and determination of UV filters in environmental water samples by Lin-ke Xue; Wei-wei Ma; Dong-xia Zhang; Xin-zhen Du (4213-4219).
In the present study, a dispersive liquid–liquid microextraction with ionic liquids (ILs) as extraction solvents was developed for the preconcentration and determination of four ultraviolet (UV) filters from different environmental water samples. Ultrasound-assisted dispersion of the ILs in the water phase was employed. The UV filters were easily concentrated into the ionic liquid phase. This technique combined the process of extraction and concentration of the analytes into one step and avoided the use of more toxic halogenated solvents. Affecting factors including the type and volume of the ILs and disperser solvents, ultrasonic time, centrifugation time, ionic strength and pH of aqueous samples were optimized. The extracts were directly analyzed by high-performance liquid chromatography coupled with a diode array detector. Under the optimized conditions, the current method provided good repeatability (RSDs < 7.6%, n = 5) and high enrichment factors in the range of 492–834. The limits of detection (LOD) for the UV filters were in the range of 0.06–0.16 ng mL−1. The linearities were between 0.2 and 500 ng mL−1 for 2-hydroxy-4-methoxybenzophenone, 0.5 and 500 ng mL−1 for 2-ethylhexyl 4-(N,N-dimethylamino) benzoate, 0.4 and 500 ng mL−1 for 2-ethylhexyl-4-methoxycinnamate, and 0.5 and 500 ng mL−1 for 2-ethylhexyl salicylate, respectively. The current procedure was successfully applied to simultaneous analyses of four UV filters in environmental water samples. For all analyzed samples, the established method has allowed fast and reliable preconcentration and determination of these UV filters with simple sample pre-treatment requirements.
Encapsulation of fluidic tubing and microelectrodes in microfluidic devices: integrating off-chip process and coupling conventional capillary electrophoresis with electrochemical detection by Vedada Becirovic; Steven R. Doonan; R. Scott Martin (4220-4229).
In this paper, an approach to fabricate epoxy or polystyrene microdevices with encapsulated tubing and electrodes is described. Key features of this approach include a fixed alignment between the fluidic tubing and electrodes, the ability to polish the device when desired, and the low dead volume nature of the fluidic interconnects. It is shown that a variety of tubing can be encapsulated with this approach, including fused silica capillary, polyetheretherketone (PEEK), and perfluoroalkoxy (PFA), with the resulting tubing/microchip interface not leading to significant band broadening or plug dilution. The applicability of the devices with embedded tubing is demonstrated by integrating several off-chip analytical methods to the microchip. This includes droplet transfer, droplet desegmentation, and microchip-based flow injection analysis. Off-chip generated droplets can be transferred to the microchip with minimal coalescence, while flow injection studies showed improved peak shape and sensitivity when compared to the use of fluidic interconnects with an appreciable dead volume. Importantly, it is shown that this low dead volume approach can be extended to also enable the integration of conventional capillary electrophoresis (CE) with electrochemical detection. This is accomplished by embedding fused silica capillary along with palladium (for grounding the electrophoresis voltage) and platinum (for detection) electrodes. With this approach, up to 128 000 theoretical plates for dopamine was possible. In all cases, the tubing and electrodes are housed in a rigid base; this results in extremely robust devices that will be of interest to researchers wanting to develop microchips for use by non-experts.
Evaluation of electrospun fibers as solid phase extraction sorbents for sample preparation in HPLC-MS/MS confirmatory doping control analysis of dexamethasone and betamethasone by Tania Possi-Pezzali; Samuel Chigome; Alejandra Rodríguez-Haralambides; Nelson Torto (4230-4237).
The aim of the present work was to evaluate the possibility of a fast, simple, and greener sample preparation method using electrospun fibers as SPE sorbents and its application for doping control analysis. Electrospun polymer fibers of polystyrene with smooth morphology (1.3 μm average diameter) were used as sorbent materials for the fabrication of miniaturized solid phase extraction devices. A microcolumn SPE device (10 mg of electrospun fibers packed in a 200 μL pipette tip) and a SPE disk device (10 mg of electrospun fibers packed in a 500 μL polypropylene barrel) were used. Their performance was evaluated using dexamethasone and betamethasone as model analytes for the analysis of drug residues in biological samples. A qualitative confirmatory method for the detection of these glucocorticosteroids by HPLC-MS/MS in human urine was developed using electrospun microfibers for sample clean-up and pre-concentration. The limit of detection for both analytes was 10 ng mL−1 in urine matrix, and the resulting analytical method is at the same time fit for purpose (complying with strict requirements of doping control international organizations), simple (using tip-based microcolumns) and has a greener footprint (using very small amounts of organic solvents).
Assessment of recombinant human erythropoietin by alternative bioassay and its correlation with liquid chromatography methods by Renato Schutkoski; Ricardo B. Souto; Guilherme Z. Calegari; Luma I. Elsenbach; Larissa P. Porto; Vanessa Schramm; Fernanda P. Stamm; Sérgio L. Dalmora (4238-4243).
Biotechnology-derived erythropoietin is a sialoglycoprotein, which stimulates erythropoiesis, and it is clinically used for the treatment of anaemia related to chronic renal failure. N-Acetylneuraminic acid content was quantified by a reversed-phase liquid chromatography method with fluorescence detection giving values higher than 108.74 ng μg−1. An alternative in vitro TF-1 cell proliferation bioassay was studied showing a lower mean difference of the estimated potency of 2.67%, compared to the normocythaemic mice bioassay, with non-significant differences (p > 0.05). Biopharmaceutical products were also analyzed by validated reversed-phase and size-exclusion liquid chromatography methods and compared to the in vivo bioassay, showing lower mean differences of the content/potencies of 2.11 and 1.21%, respectively. Higher molecular mass forms and deamidated/sulphoxide forms showed mean bioactivities reduced to about 10%, for both. The TF-1 cell culture assay in conjunction with the determination of sialic acids represents an advance that can be correlated with the normocythaemic mice bioassay and the physicochemical methods, allowing for the establishment of alternative methods, which can be applied to monitor the stability, quality control, and thereby ensuring the therapeutic efficacy of the biological medicine.
Validation of an immunoassay for fast screening of bisphenol A in canned vegetables by Juan J. Manclús; María J. Moreno; Ángel Montoya (4244-4251).
The effects of BPA exposure on human health are an issue of concern and controversy. In the present work, the validation for the first time of a monoclonal antibody-based enzyme-linked immunoassay (ELISA) for BPA determination in canned vegetables is described, using HPLC as the reference method. From a collection of monoclonal antibodies, a high-sensitivity immunoassay was selected on the basis of its tolerance to organic solvents and the influence of matrix effects. This ELISA displayed a limit of detection of 3 μg kg−1 of BPA in the whole product of canned vegetables and 15 μg L−1 of BPA in the liquid portion. For assay validation, processed vegetables were fortified with BPA at 10, 50, and 200 μg kg−1. Sample treatment rendered crude and purified extracts. Purified extracts were analyzed by HPLC and ELISA, while crude extracts could be analyzed only by ELISA. Depending on the crop and the fortification level, good recoveries were obtained for both methods: 70.6–105% for HPLC and 61.4–115% (purified extracts) or 82–120% (crude extracts) for ELISA. HPLC was more precise than ELISA. Finally, crude extracts of canned peas were analyzed by ELISA. Results (33–62 μg kg−1) also compared well with those obtained by HPLC on purified extracts (23–44 μg kg−1). In all samples, BPA concentration was significantly lower than the specific migration level of 600 μg kg−1 established by the European Commission. Therefore, the ELISA herein validated constitutes a sensitive, fast, and high-throughput technique for BPA screening in canned vegetables.
Effect of 3d transition metals on gas sensing characteristics of perovskite oxides LaFe1−xCoxO3 by Ho Truong Giang; Ha Thai Duy; Pham Quang Ngan; Giang Hong Thai; Do Thi Anh Thu; Do Thi Thu; Nguyen Ngoc Toan (4252-4257).
Nano-crystalline powders of LaFe1−xCoxO3 (with x = 0.0; 0.1; 0.2; 0.3 and 0.4) were synthesized by the sol–gel technique. By X-ray diffraction examination, it was concluded that Fe in octahedra (BO6) of the perovskite LaFe1−xCoxO3 oxides could be replaced by Co. The gas-sensing characteristics of LaFe1−xCoxO3 based thick-film sensors were investigated in various gases including carbon monoxide (CO), methane (CH4), propane (C3H8), n-hexane (C6H14) and nitrogen dioxide (NO2). It was found that the electrical conductance and gas-sensing characteristics of the LaFe1−xCoxO3 oxides were strongly influenced by the ions of 3d transition metals, particularly Co ions, with the possibility to exist in different valence states (Co2+ and Co3+). It was also observed that the LaFe1−xCoxO3 sensors had high sensitivity and selectivity to CO with Co contents (x) of around 0.1. The decrease in stability of the LaFe1−xCoxO3 sensors upon increasing the Co content was discussed in relation to the stability and reversibility of the valence states of Co and Fe ions.
Compatible buffer for capillary electrophoresis and matrix-assisted laser desorption/ionization mass spectrometry by Hong-Xu Chen; Jean-Marc Busnel; Liang Qiao; Natalia Gasilova; Xin-Xiang Zhang; Hubert H. Girault (4258-4262).
A compatible buffer system for coupling of capillary electrophoresis (CE) with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) was developed. The employed interface consists of a robot to drive a silver-covered separation capillary and an AnchorChip MALDI-MS target. The outlet of the capillary is grounded and connected to the pre-deposited buffer droplet on the MALDI target to make the electric connection and allow sample crystallization for MALDI-MS. The possibility of using only one buffer already containing the matrix for MALDI-MS for separation and ionization was investigated and tested on protein and peptide samples. The results show that the proposed buffer system is suitable for CE-MALDI-MS coupling, simplifies the traditional buffer mixing steps in off-line CE-MALDI-MS protocols, and is therefore highly promising for on-line analysis.
Rapid determination of silicone oil lubricant in elastomeric closures by ICP-OES by Éder José dos Santos; Amanda Beatriz Herrmann; Ralph Edward Sturgeon; Jessee Severo Azevedo Silva; Adilson José Curtius (4263-4267).
A rapid method for determination of silicone oil in elastomeric closures of injection syringes by inductively coupled plasma optical emission spectrometry (ICP-OES) is presented. The silicone oil was extracted from the intact closure using a mixture of methyl isobutyl ketone and 1-pentanol, no further sample treatment was necessary. Quantitation was based on response from Si(i) at 288.158 nm using external calibration with standard solutions of silicone oil dissolved in the same extraction mixture. A supplemental flow of oxygen was used to decrease background interference, providing a detection limit (3s, n = 10) of 0.05 mg of silicone per L. The LOQ (10s, n = 10) was 0.15 mg silicone per L, equivalent to 3.8 μg silicone/sample of elastomeric closure, based on 25 mL of extraction solvent per closure. The same samples were also analyzed by high-resolution flame atomic absorption spectrometry (HR-CS F-AAS), providing results similar to those obtained by ICP-OES. Spike recoveries of 97–104% demonstrated the accuracy of the methodology. Precision, expressed as the relative standard deviation, was 0.7–3.0% under conditions of repeatability and 0.7–3.3% for reproducibility. This simple procedure has been adopted by the Institute of Technology of Paraná– TECPAR (Curitiba, Brazil).
Vapor discrimination by dual-laser reflectance sensing of a single functionalized nanoparticle film by Kee Scholten; Karthik Reddy; Xudong Fan; Edward T. Zellers (4268-4272).
Sorption-induced changes in the localized surface-plasmon resonance (LSPR) of an n-octanethiolate-monolayer-protected gold nanoparticle film on a Si chip are exploited to differentiate two volatile organic compounds (VOC) with a single sensor. Probing the film with 488 nm and 785 nm lasers gave reflectance sensitivity ratios at the two wavelengths of 0.68 and 0.80 for toluene and n-heptane, respectively, permitting their discrimination. Swelling-induced increases in inter-particle distance appear to predominate over changes in the refractive index of the inter-particle matrix in the sensor responses. The corresponding ratios of sensitivities with a reference film of polydimethylsiloxane did not differ for the two vapors. Approaches for extending the capability for VOC discrimination by use of arrays of such LSPR sensors are discussed, along with the advantages of employing this simple platform in compact, field-deployable environmental VOC monitoring systems.
Back cover (4273-4274).