Analytical Methods (v.6, #24)

Front cover (9517-9518).

Contents list (9519-9531).

Microchip nonaqueous capillary electrophoresis of saturated fatty acids using a new fluorescent dye by M. L. Cable; A. M. Stockton; M. F. Mora; K. P. Hand; P. A. Willis (9532-9535).
We demonstrate nonaqueous labeling and separation of the full range of short to long saturated fatty acids (C2 to C30) for the first time on a microfluidic device. A new fluorescent dye, Pacific Blue hydrazide, labels the carboxylic acid in a two-step, one-pot reaction to enable detection via laser-induced fluorescence at 405 nm excitation. Limits of detection for C10 to C30 acids range from 0.9 to 5.7 μM. Fatty acids were successfully quantified in a sediment sample from the ‘Snake Pit’ hydrothermal system of the Mid-Atlantic Ridge, demonstrating the potential of this method to help characterize microbial communities through targeted biomarker analysis. Such a technique could also be utilized to differentiate between abiotic and biotic compounds in the search for life beyond Earth.

Raman spectral signatures for the differentiation of benzodiazepine drugs by Gemma Montalvo; Lucía López-Melero; Fernando Ortega-Ojeda; María Ángeles Peña; Carmen García-Ruiz (9536-9546).
The identification of benzodiazepine drugs is important in the forensics field because they are used in drug-facilitated crimes. Raman spectroscopy has been proven as a non-invasive, fast and reliable technique highly promising for the analysis of drug products. Until recently, attention has been paid to active ingredients, but the spectral drug product signature has rarely been used in spite of having potential valuable information. In this work, confocal Raman microscopy was used to obtain the spectral signature of the most widely used benzodiazepine products. Firstly, the study aimed at determining appropriate Raman mapping spectra to obtain each benzodiazepine signature with low sampling error. Then, PCA scores and loadings showed that the variability, measured on the variance, among batches of the same benzodiazepine drug was similar to the variability of the spectral signature of the same tablet (or capsule content) and the same batch, mainly attributed to the heterogeneity of such drug products. Interestingly, differentiation among doses of the same active ingredient (AI), benzodiazepine drugs with different AIs manufactured by the same pharmaceutical company, and drugs with the same AI but manufactured by different companies were demonstrated. It is remarkable that for low doses, the active ingredient is almost absent of the spectral signature, but the differentiation is mainly achieved by excipients. As a consequence, the spectral signature obtained by confocal Raman microscopy can be used for discriminating among these benzodiazepine drugs without requiring a clearly identifiable band related to the active ingredient in the corresponding Raman spectra.

Rapid fabrication of self-assembled interfacial film decorated filter paper as an excellent surface-enhanced Raman scattering substrate by Wu-Li-Ji Hasi; Shuang Lin; Xiang Lin; Xiu-Tao Lou; Fang Yang; Dian-Yang Lin; Zhi-Wei Lu (9547-9553).
An excellent paper-based SERS substrate was easily fabricated by utilizing interfacial films formed in the mixture of Ag colloid and CH2Cl2. This interfacial film coating method significantly improves the fabrication efficiency of SERS substrates. The substrate has a high coverage of silver nanoparticles (Ag NPs) and can be tailored to arbitrary shapes. The SERS substrate exhibits high sensitivity (EF ∼ 4 × 107) and gives uniform SERS signals with a relative standard deviation (RSD) of 8.08% (spot-to-spot) and 8.65% (batch-to-batch) using 4-mercaptobenzoic acid (4-MBA) as a Raman probe. In addition, this SERS substrate with excellent stability can be stored for more than 30 days. The limit of detection was found to be 10−8 M for 4-MBA. In general, this SERS substrate is qualified for rapid and simple trace detection of various analytes.

Simple fluorescence-based detection of Cr(iii) and Cr(vi) using unmodified gold nanoparticles by Elavarasi M; Sruthi Ann Alex; N. Chandrasekaran; Amitava Mukherjee (9554-9560).
We present herein a fluorescence-based method for the determination of both the trivalent and hexavalent forms of chromium in aqueous solutions using unmodified gold nanoparticles. The concept of the sensor was designed based on the aggregation of gold nanoparticles (Au NPs) by Cr(iii), which results in a color change from red to blue and the appearance of a new secondary peak at 714 nm. The complexation of Au NPs by Cr(iii) consequently leads to the quenching of the fluorescence intensity of Au NPs, which is proportional to the concentration of Cr(iii). The Au NP aggregation upon the addition of Cr(iii) is well correlated with the mean hydrodynamic size measurements and scanning electron microscopy images. The system was found to possess a good linear correlation between the chromium concentration and the degree of reduction of fluorescence intensity (R2 = 0.989) in the range of 10−7–10−3 M with an excellent limit of detection of 10−7 M (5 ppb). The prospective application of the as-designed probe for environmental sensing can be highlighted because it has been found to successfully determine the chromium concentration in real water samples. Our method has the advantage of cost-effectiveness and does not use any additional fluorophores for the sensitive detection of both the forms of chromium.

Determination of sulfonylurea herbicides in soil by ionic liquid-based ultrasonic-assisted extraction high-performance liquid chromatography by Rui Yan; Fulong Ju; Haoyu Wang; Changhua Sun; Hanqi Zhang; Mingyuan Shao; Yuzhi Wang (9561-9566).
A high-performance liquid chromatography method for determination of sulfonylurea herbicides in soil has been developed. Prior to the determination, sample preparation was performed by ionic liquid-based ultrasonic-assisted extraction (IL-based UAE). Dried soil powder was mixed with a room temperature ionic liquid, [C6MIM][BF4], to form a suspension, and then ultrasonic extraction was performed in a water bath at ambient temperature. The chromatographic separation was performed using a C18 chromatographic column with gradient elution mode. The method was validated by evaluating the repeatability, linearity, precision, and applicability. The limits of detection ranged from 7.7 ng g−1 to 11.3 ng g−1 and the limits of quantification were between 25.6 ng g−1 and 37.6 ng g−1. The calibration curves showed a good linear relationship (r > 0.9990) in the concentration ranges of 50.0–25 000 ng g−1 for nicosulfuron and 50.0–5000 ng g−1 for metsulfuron-methyl, bensulfuron-methyl and pyrazosulfuron-ethyl. The recoveries ranged from 81.1 to 100.1% with relative standard deviations lower than 7.44%. The IL-based UAE is free of volatile organic solvent, and consumes less sample, time and solvent, compared with regular ultrasonic and Soxhlet extractions. There was no obvious difference in the extraction recoveries of sulfonylurea herbicides obtained by the three methods.

A new strategy for investigation of metabolic fingerprints in complex systems was developed based on a combination of open column chromatography, reversed-phase high-performance liquid chromatography and k-means clustering. A simplex centroid mixture design with four solvents, hexane, dichloromethane, ethyl acetate and methanol, was applied to a crude extract of the Bauhinia variegata L. to gradually change the mobile phase polarity of the open column. K-means clustering was used to screen the profiles of the 3033 spectra from high-performance liquid chromatography with diode array detection data. The seventeen k-means clusters were discriminated into three groups. The largest one containing 2617 (86.3%) spectra has a strong absorbance band around 210 nm that is commonly found in many naturally abundant compounds. The smallest group contains only 134 (4.4%) spectra and has strong absorbance bands at wavelengths well above 250 nm and are potentially interesting for further metabolic studies and fingerprinting. The other group judged to have spectral profiles intermediate between those of the other two contains 282 (9.3%) spectra. Ternary and quaternary mixtures of the statistical design provided potentially useful information for fingerprinting Bauhinia variegata L. extracts relative to what could be obtained using only pure solvents and binary mixtures that are commonly employed in open column chromatography.

Rapid adulteration detection for flaxseed oil using ion mobility spectrometry and chemometric methods by Qian Shuai; Liangxiao Zhang; Peiwu Li; Qi Zhang; Xiupin Wang; Xiaoxia Ding; Wen Zhang (9575-9580).
To prevent the potential adulteration of flaxseed oil with high amounts of nutritional components, a simple and rapid adulteration detection method was proposed based on ion mobility spectrometry (IMS). After dilution in n-hexane, the edible oil sample was analyzed by IMS for 20 s. Subsequently, the multivariate statistical methods, including principal component analysis (PCA) and recursive support vector machine (R-SVM), were employed to establish a discriminant model for authentic and adulterated flaxseed oils. The cross validation results indicated that the R-SVM model could identify adulterated flaxseed oil samples (≥5%) with a high accuracy of 93.1%. Therefore, IMS could be used as an important tool to protect customers from adulterated flaxseed oil.

The analysis of faecal sterols in sediment samples by HPLC-UV using ultrasound-assisted treatment by Michele F. Resende; Mellina D. R. Santos; Renato C. Matos; Maria A. C. Matos (9581-9587).
A method was developed for the analysis of faecal sterols in sediment samples by ultrasound-assisted extraction and quantification by HPLC with a UV detector. A reversed-phase C18 column was used to develop the method and optimal conditions were employed for elution under isocratic conditions using a methanol/THF/water (83 : 9 : 8) as the mobile phase. Direct detection of sterols by HPLC is difficult, so a derivatization procedure using benzoyl chloride was performed. A sample treatment using ultrasound-assisted extraction with 40 mL of methylene chloride–methanol (1 : 1) for 30 min without a clean up step was developed. The recoveries obtained ranged from 65 to 89% for the sample spike and from 67 to 101% for the blank spike. The detection limits ranged from 1.90 mg L−1 for β-sitosterol to 4.17 mg L−1 for epicoprostanol. Seven streams of Juiz de Fora city were analysed and the concentrations of coprostanol in the sediment samples varied between 0.01 and 14.48 μg g−1. Except for the farm forest sample stream, all others were considered contaminated by faeces using the parameters and evaluation criteria for this type of contamination.

Aripiprazole (ARP) is an atypical antipsychotic medication used for the treatment of schizophrenia and schizoaffective disorders. In this study, a new method using the chemiluminescence (CL) of tris(1,10-phenanthroline)-ruthenium(ii), Ru(phen)32+, was developed for the rapid and sensitive determination of ARP in pharmaceuticals and human plasma. The method is based on the fact that the weak chemiluminescence produced in the reaction of Ru(phen)32+ and acidic Ce(iv) is enhanced in the presence of ARP. Under the selected experimental conditions, calibration curves were linear from 1.8 to 18.0 ng mL−1 (r2 = 0.9951) and from 18 to 35 900 ng mL−1 (r2 = 0.9987). The limit of detection (LOD) was 0.9 ng mL−1 (S/N = 3). In the method proposed, the LOD was about 100 times lower than the therapeutic concentration of ARP. The percent relative standard deviations (%RSDs) for 11 repeated measurements of 180 and 720 ng mL−1 of ARP were 4.5 and 5.2%, respectively. The sampling rate for analysis was 70 samples per hour. The proposed method was successfully applied to the assay of commercial tablets containing the drug, and the results were in accordance with those obtained with the reference method. The method was further applied to the determination of the drug in plasma samples. The possible CL reaction mechanism was also discussed briefly.

Investigating the chemical reactions at the surface of quantum dots (QDs) is fundamental for applications of QDs in ionic environments. On the basis of our recent report about the discriminative detection of Mn(ii) from Cu(ii) via QD fluorescence sensing, we herein focused on the QD surface chemical reactions with Mn(ii) or Cu(ii) at different QD surface modification conditions. Two types of QDs were used. One is well modified QDs with a surface rich in Cd-ligands complexes. Another is moderately modified QDs with both bared Te atoms and Cd-ligand complexes on the surface. Our results indicated that well modified QDs underwent a chemical reaction with Cu(ii), namely, the substitution of Cd from QDs by Cu(ii). In this case, the results of discriminative detection of Mn(ii) from Cu(ii) is always believable. For moderately modified QDs in comparison, it appears there is a new reaction manner via combination of bared Te atoms with Cu(ii) or Mn(ii). This new reaction manner occurs mainly around pH 10.3. Consequently, the results of discriminative detection of Mn(ii) from Cu(ii) via moderately modified QDs is not believable.

An automated simple analyzer system for the extraction of cationic surfactants as an ion-pair with disulfine blue dye is described based on the technique in-syringe magnetic stirring-assisted dispersive liquid–liquid micro-extraction. The use of chloroform as an extraction solvent denser than water required the operation of the syringe pump upside-down. The remaining air cushion inside the syringe allowed emptying the syringe completely and reducing the dead volume significantly compared to previous studies. Since the stirring bar placed inside the syringe to obtain a closed yet size-adaptable mixing chamber remains at the same position, the former magnetic stirring bar driver was simplified. The new system configuration further enabled automated in-syringe washing of the organic phase with water and barium acetate solution to minimize interference. High signal repeatability with <5% RSD was achieved both for extraction as well as for double organic phase washing. Only 220 μL of the extraction solvent and 4 mL of the sample were required for simple extraction achieving a detection limit below 30 nmol L−1 and a linear response up to 1 μmol L−1 of cetyltrimethylammonium bromide. The time of analysis was 240 s for simple extraction. Considerable reduction of interference was achieved by extract washing up to 545 s. Analyte recovery in real water samples was 95.6 ± 7.0% on applying extract washing.

A water soluble pyridine containing a Schiff base as chemosensor was designed and then synthesised. The chemosensor (L) was synthesized by reacting pyridoxal and 2-aminoethanol and then comprehensively characterized using elemental analysis, spectroscopic methods (infrared, ultraviolet-visible, nuclear magnetic resonance (1H-NMR and 13C-NMR) spectroscopy), electrospray ionization mass spectroscopy, and single crystal X-ray crystallography. The designed compound showed excellent specificity and sensitivity (detection limit = 4.18 × 10−6 M) towards Ag+ ions in preference to other interfering cations (Ca2+, Co2+, Cu2+, Fe2+, Fe3+, Hg2+, VO2+, K+, Li+, Mn2+, Na+, Ni2+, Pb2+ and Zn2+) in aqueous solution. The (L) showed a selective chromogenic behavior towards Ag+ ions by changing the color of the solution from light yellow to red, a change which can be detected with the naked eye. A simple and cost effective test kit was prepared for the detection of silver ion in water samples. Time-dependent density functional theory calculations were carried out to help understand the sensing mechanism.

Highly sensitive “signal on” plasmonic ELISA for small molecules by the naked eye by Chifang Peng; Xiaohui Duan; Gabriel Wafala Khamba; Zhengjun Xie (9616-9621).
Based on the H2O2-mediated generation of gold nanoparticles, a colorimetric catalase nanosensor was developed and utilized as a signal output in a catalase-labelled immunoassay. Methyltestosterone (MT), which is used illegally as a growth promoter during the cattle production cycle, was selected as a small molecule model in this new ELISA development. As a result, a “signal on” plasmonic ELISA for MT was established. This plasmonic ELISA can quantitatively detect MT by spectrophotometry with a 50 times higher sensitivity than the traditional ELISA. In addition, it allows the highly sensitive and easily qualitative detection of MT by the naked eye. This plasmonic direct competitive ELISA can be utilized for developing cost-effective and sensitive ELISA against various small molecules by the naked eye.

Enhancement of osteogenic properties of bone substitutes is best achieved by the covalent attachment of appropriate biomolecules, e.g. proteins and peptides, on amino-functionalized implant materials. Measurement of the free amino surface density of these materials is mandatory before derivatization. Two photometric methods were developed to assay the free amino groups of organosilane molecules covalently grafted onto hydroxyapatite and silicon-substituted hydroxyapatite ceramic surfaces. Reaction of amino-derivatized apatites with ninhydrin led to the formation of Ruhemann's purple quantified by the absorbance at 586 nm. Alternatively, ceramics were reacted with Fmoc-derivatized amino acids in the presence of piperidine, leading to the dibenzofulvene–piperidine adduct measured at 301 nm. Both methods allow the detection of free amino groups down to 1.0 × 10−8 mol g−1 of apatite-ceramics and, since they are conducted under non-acid conditions, preserve the acid-sensitive structure of hydroxyapatite.

Rapid, on-site detection of residual explosives based on a lab-in-a-capillary and UV fiber sensor by Ruliang Wang; Guang Yang; Junqi Zhang; Qi Li; Rongxin Fu; Jiancheng Ye; Tongzhou Wang; Ying Lu; Hong Zhou; Guoliang Huang (9628-9633).
An integrated portable system based on a lab-in-a-capillary and a UV (190–400 nm) reflected fiber sensor was demonstrated for on-site detection of trace amounts of explosives in a micro-nanoliter droplet. The filtration and measurement of the residual explosive sample were integrated in a compact device. The micro-droplet (1 nL–1 μL) was loaded onto the capillary-end by the equilibrium between gravity and negative air pressure for UV spectral analysis. Moreover, a new mixed spectrum decomposition algorithm (MSDA) was used to calculate the concentration of multiple explosives in the soil of the explosion site. This system for real-time explosive analysis features a short sample preparation and analysis time (<5 s), low sample consumption (10 nL), wide detection range (1–250 ng μL−1), low detection limit (<10 pg), and is easy to disassemble and clean, which fulfills the requirements for on-site explosive detection.

Near infrared (NIR) spectroscopy combined with high-performance liquid chromatography (HPLC) was applied to discriminate the difference of aromatic vinegar produced during different seasons. 120 samples from 4 seasons were collected, different data preprocessing methods such as standard normal variate transformation (SNV), multiplicative scatter correction (MSC), first derivatives (D1) and second derivatives (D2) were used and linear discriminant analysis (LDA), support vector machine (SVM) and K-nearest neighbor (KNN) models were used to identify the season the aromatic vinegar was produced in. The best result was obtained by the SVM approach with SNV preprocessing, with recognition rate of 100% in training set and test set. The contents of lactic acid, malic acid, l-pyroglutamic acid in aromatic vinegar were analyzed quantitatively through NIR spectroscopy and HPLC combined with partial least squares (PLS) model, backward interval partial least squares (bi-PLS) and back propagation artificial neural network (BP-ANN). The detection of nonlinearity indicated that NIR spectra and the content of lactic acid, malic acid and l-pyroglutamic acid were non-linear and the best results were obtained by BP-ANN model: for lactic acid, optimal PCs was 10, the correlation coefficient (R) for prediction was 0.9342 and root mean square error for prediction (RMSEP) was 0.3310; for malic acid, optimal PCs was 8, R was 0.9337, RMSEP was 0.0557; for l-pyroglutamic acid, optimal PCs was 10, R was 0.9229, RMSEP was 0.0062. The results indicate that NIR spectroscopy could be successfully applied as a rapid method not only to identify the season the aromatic vinegar was produced in, but also to determine the contents of lactic acid, malic acid, l-pyroglutamic acid in aromatic vinegar combined with the BP-ANN model simultaneously.

Classification of cervical cytology for human papilloma virus (HPV) infection using biospectroscopy and variable selection techniques by Kássio M. G. Lima; Ketan Gajjar; George Valasoulis; Maria Nasioutziki; Maria Kyrgiou; Petros Karakitsos; Evangelos Paraskevaidis; Pierre L. Martin Hirsch; Francis L. Martin (9643-9652).
Cervical cancer is the second most common cancer in women worldwide. We set out to determine whether attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy combined with principal component analysis–linear discriminant analysis (PCA–LDA) or, variable selection techniques employing successive projection algorithm or genetic algorithm (GA) could classify cervical cytology according to human papilloma virus (HPV) infection [high-risk (hr) vs. low-risk (lr)]. Histopathological categories for squamous intraepithelial lesion (SIL) were segregated into grades (low-grade vs. high-grade) of cervical intraepithelial neoplasia (CIN) expressing different HPV infection (16/18, 31/35 or HPV Others). Risk assessment for HPV infection was investigated using age (≤29 years vs. >30 years) as the distinguishing factor. Liquid-based cytology (LBC) samples (n = 350) were collected and interrogated employing ATR-FTIR spectroscopy. Accuracy test results including sensitivity and specificity were determined. Sensitivity in hrHPV category was high (≈87%) using a GA–LDA model with 28 wavenumbers. Sensitivity and specificity results for >30 years for HPV, using 28 wavenumbers by GA–LDA, were 70% and 67%, respectively. For normal cervical cytology, accuracy results for ≤29 years and >30 years were high (up to 81%) using a GA–LDA model with 27 variables. For the low-grade cervical cytology dataset, 83% specificity for ≤29 years was achieved using a GA–LDA model with 33 wavenumbers. HPV16/18 vs. HPV31/35 vs. HPV Others were segregated with 85% sensitivity employing a GA–LDA model with 33 wavenumbers. We show that ATR-FTIR spectroscopy of cervical cytology combined with variable selection techniques is a powerful tool for HPV classification, which would have important implications for the triaging of patients.

An analytical methodology has been developed for the speciation of Cr(iii) and Cr(vi) in soil/sediments. The species of interest were extracted from samples using a solution containing 0.1 M EDTA, 1% tetrabutyl ammonium bromide (TBAB) and a little HF in a domestic microwave oven. The conditions for the quantitative extraction of the Cr species from sediments were optimized. The separation of anionic Cr(vi) from the sediment extract was carried out using the sulfate form of Dowex-1 at pH 4.5. Though the extract contained the anionic EDTA complex of Cr(iii), it was quantitatively eluted. The adsorbed Cr(vi) was eluted with 2 M HNO3. The determination of the separated Cr(vi) and Cr(iii) in the effluent, and total Cr in the extract was carried out using ICP-OES. The recovery of the total Cr from the original samples was 96–99% and that of Cr(iii) and Cr(vi) spiked was 97–102% with an RSD in the range of 5–6%. A developed methodology has been applied for the speciation of Cr in a certified reference material stream sediment (GBW-07312) and also four real world samples: two sediments collected from the Hussain Sagar lake, Hyderabad, India and two soils collected near the Uranium Corporation of India Limited (UCIL), Tummalapalli, Kadapa, India. The total concentration of Cr in the extract was in good agreement with the certified value of the stream sediment and with the complete dissolution method in case of the real world samples. The limit of detection of Cr(vi) was 0.02 mg L−1, which corresponding to a detection limit of 5.0 mg kg−1 for this method.

An optimized method based on MAE-SPE-GC-MS for the analysis of thirteen PBDEs in airborne particles by X. Li; X. M. Li; X. X. Yang; Q. Li; B. Huang; X. J. Pan (9658-9666).
An efficient and reliable analytical method has been developed for the determination of polybrominated diphenyl ethers (PBDEs) in atmospheric particulates collected by ultra-fine glass fibre filters. Thirteen PBDEs in atmospheric particulates were extracted through a developed method and determined by gas chromatography-mass spectrometry (GC-MS). Compared with the classical Soxhlet method and multi-layer silica column purification procedure, the developed method, including microwave assisted extraction (MAE) and solid phase extraction (SPE) procedures, made the pretreatment procedure of atmospheric particulates samples more automatic and faster. The four important conditions of MAE procedure (extraction solvent, solvent volume, extraction temperature and holding time) and three important conditions of SPE procedure (SPE cartridge, elution solvent and pH) were carefully studied and improved. The method achieved good repeatability and reproducibility with RSDs ranging from 2.0% to 11% for all target PBDEs in atmospheric particulate samples. Satisfactory recoveries for spiked particulate samples ranged from 74.0% to 112%. The limits of detection (LOD) and limits of quantification (LOQ) ranges for filter samples were from 0.11 (BDE-17) to 1.23 ng g−1 dw (BDE-209) and from 0.37 (BDE-17) to 4.10 ng g−1 dw (BDE-209), respectively. The developed method has been successfully demonstrated to determine the concentrations of the target PBDEs in atmospheric particulates from one of the state air quality controlling sites in Kunming, China. The results showed that the concentration range of target PBDEs was from 4.97 to 376 ng g−1 dw. BDE-28 (27.9 ng g−1 dw), BDE-71 (35.4 ng g−1 dw), BDE-190 (265.4 ng g−1 dw) and BDE-209 (375.6 ng g−1 dw) were the four dominant PBDEs at the sampling site.

This article focuses on the development of an analytical procedure for the photometric determination of vanadium in fresh and mineral waters, implemented employing a downsized multicommuted flow analysis approach. A flow system module using solenoid mini-pumps for fluid propelling and a light emitting diode (LED) based photometer were handled employing a microcontroller (PIC18F). Aiming to improve sensitivity, the flow analysis module and the photometer were designed to allow the coupling of a flow cell with an optical pathlength of 150 mm. The photometric procedure was based on the reaction of V(iv) with eriochrome cyanine R, which formed a compound that presented maximum absorption at 560 nm. Samples of river water and mineral water were processed with the intention to assess the effectiveness of both equipment setup and analytical procedure. The proposed setup presented good overall performance including a linear response (r = 0.997) comprising the concentration range of 0.02 to 1.50 μg mL−1 vanadium; reagent consumption of 11.6 μg eriochrome cyanine R and 8.6 mg ascorbic acid per determination; and a detection limit of 13 μg L−1 vanadium. Other useful features including a relative standard deviation of 0.87% (n = 10), a sampling throughput of 47 determination per hour and a waste generation of 2.4 mL per determination were also achieved.

Rapid and nondestructive evaluation of fish freshness by near infrared reflectance spectroscopy combined with chemometrics analysis by Ran Ding; Xingyi Huang; Fangkai Han; Huang Dai; Ernest Teye; Fubin Xu (9675-9683).
Rapid and nondestructive measurement of freshness is essential for the control of fish and the quality and safety of its products. In this study, K value was measured by high performance liquid chromatography (HPLC) and employed as an index of fish freshness. The prediction models of the silver chub freshness were developed using Fourier Transform Near Infrared Reflectance Spectroscopy (FT-NIRS) with Several Partial Least Squares (PLS, i-PLS, Si-PLS), Support Vector Machines Regression (SVMR) and Synergy interval plus Support Vector Machine Regression leading to Si-SVMR. By comparison, the performance of Si-SVMR model was superior to the others for the prediction of K value, where RMSECV = 0.027095 and Rc = 95.59% for the calibration set, whereas RMSEP = 0.036525 and Rp = 93.74% for the prediction set. The results indicated that FT-NIR spectroscopy together with Si-SVMR model could be a reliable method for the detection of fish freshness.

Chemiluminescence diminishment on a paper-based analytical device: high throughput determination of β-agonists in swine hair by Xu Chen; Yong Luo; Bo Shi; Xianming Liu; Zhigang Gao; Yuguang Du; Weijie Zhao; Bingcheng Lin (9684-9690).
β-Agonists are a group of illegal but widely used feed additives in the stockbreeding industry. In order to achieve simple-to-use, fast and high-throughput testing of this banned chemical, herein we suggest a paper-based analytical device on which a chemiluminescence diminishment method was performed. In this approach, extracts from swine hair samples as well as luminescent reagents, such as luminol and potassium periodate solution, in a low volume were applied to our device. It was found that the light emission was diminished by the β-agonists extracted from the swine hair samples. The degree of diminishment is proportional to the concentration of the β-agonists from 1.0 × 10−5 to 1.0 × 10−8 mol L−1. Also, the concentrations of solutions for chemiluminescence were optimized. The mechanism and reaction kinetics of chemiluminescence were discussed as well. The detection limit was obtained as 1.0 × 10−9 mol L−1, and recoveries from 96% to 110% were achieved, both of which suggested that our method will be favourable in field applications for swine hair samples.

Qualitative and quantitative analysis of Angelica sinensis using near infrared spectroscopy and chemometrics by Boxia Li; Chengqi Wang; Lili Xi; Yuhui Wei; Haogang Duan; Xinan Wu (9691-9697).
A new, rapid analytical method using near infrared spectroscopy (NIRS) was developed to differentiate Radix Angelicae sinensis samples from five different geographic origins, and to determine the contents of ethanol extract and ferulic acid in the samples. The scattering effect and baseline shift in the NIR spectra were corrected and the spectral features were enhanced by several pre-processing methods. By using principal component analysis (PCA), the grouping homogeneity and sample cluster tendency were visualized. Furthermore, random forests (RF) was applied to select the most effective wavenumber variables from the full NIR variables and to build the qualitative models. Finally, the genetic algorithm optimization combined with multiple linear regression (GA-MLR) was applied to select the most relevant variables and to build the ethanol extract and ferulic acid quantitative models. The results showed that the correlation coefficients of the models are Rtest = 0.83 for ethanol extract and Rtest = 0.81 for ferulic acid. The outcome showed that NIRS can serve as routine screening in the quality control of chinese herbal medicine.

Traumatic brain injury (TBI) has been associated with an acute stress response mediated by the sympathoadrenomedullary axis, which can be assessed by measuring glucose levels. Thus, aiming for a more convenient assay system of glucose, a novel electrochemical measurement for the sensitive detection of glucose in cerebrospinal fluid (CSF) was developed in this work in virtue of the electrodeposition of platinum nanoclusters on stable composite films constructed from carbon nanotubes (CNTs) and a core–shell organosilica@chitosan nanospheres (OrgSi@CS) modified glassy carbon electrode. The morphologies and the structures of the OrgSi@CS–CNTs composite material and platinum nanoclusters were characterized by atomic force microscopy (AFM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Cyclic voltammetries (CVs) were used to investigate the direct electrochemistry behavior between the electroactive center of glucose oxidase (GOD) and the electrode. The linear response range was determined from 1.2 × 10−6 to 1.6 × 10−3 M with a detection limit of 4.0 × 10−7 M, and the Michaelis–Menten constant (KappM) value was estimated to be 0.41 mM, indicating a high-catalytic activity for glucose. In vitro experiments were performed with clinical samples of CSF obtained from TBI patients and compared with the glucose oxidase endpoint method, which showed an acceptable measurement with enhanced speed and convenience, indicating the feasibility of the sensors for a real-time continuous monitoring in vivo.

A new analytical strategy for single extraction of metals in phosphate fertilizers by Hélen C. Rezende; Nívia M. M. Coelho (9705-9711).
A simple method using an ultrasound-assisted single extraction procedure for the determination of Cd, Pb and Cr in phosphate fertilizers by graphite furnace atomic absorption spectrometry was developed. Multivariate optimization through a factorial design and desirability functions was applied to establish a single extraction procedure for the metals. Quantitative extraction was carried out with 20 mL of a mixture of 1 mol L−1 HNO3 and 1 mol L−1 HCl applying sonication for 7.5 min. Under the optimal conditions the characteristic mass and limits of quantification were 0.54, 8.22 and 2.54 pg and 0.11, 0.90 and 0.63 μg L−1 for Cd, Pb and Cr, respectively. The relative standard deviation was less than 5%. The accuracy of the method was evaluated by comparison with the results obtained from the analysis of a multi-nutrient fertilizer (certified material NIST SRM 695) and no significant difference at the 95% confidence level was observed. The method was applied to the extraction and determination of Cd, Pb and Cr in phosphate fertilizer samples produced in Brazil and the levels found were below the maximum values established by Brazilian legislation.

A novel dispersive micro-solid phase extraction (D-μ-SPE) method is presented in this paper. The most attractive feature of this method is taking full advantage of a plastic dropper and nanoscale one-dimensional polyaniline (1D-PANI). The plastic dropper was employed as both the extraction and preconcentration device. All procedures needed in the common μ-SPE were performed in a plastic dropper without any additional devices, such as a centrifuge, magnetic field and pressure blowing concentrator. So the operating steps were simplified greatly. 1D-PANIs were used as the sorbent. The huge surface and interconnected network structure of 1D-PANIs endows them with high dispersive adsorbability and good permeability for the adsorbed analytes to be eluted. To test the feasibility of the proposed method, eight organochlorine pesticides (OCPs) were selected as the model analytes for D-μ-SPE of OCPs in water samples. A series of extraction parameters have been investigated systematically. Under optimized conditions, the method showed that the linear correlation coefficients (r) were better than 0.9971 and the limits of detection (LODs) for eight OCPs ranged from 0.0121 to 0.0468 μg L−1. The intra- and inter-day relative standard deviations (RSDs) were less than 11.9%. The recoveries of OCPs for three spiked aqueous samples ranged from 73.6 to 107.0%. The novel D-μ-SPE is promising to be an alternative sample preparation method for extracting apolar analytes in complex sample matrices because of its simplicity, low cost and high extraction efficiency.

A method based on microwave distillation (MD) and simultaneous headspace solid-phase microextraction (HS-SPME), coupled with gas chromatography-mass spectrometry (GC-MS), was developed for the rapid determination of essential oils in fruits of Alpinia oxyphylla Miq., a traditional Chinese medicine (TCM). HS-SPME conditions, including SPME fiber, desorption time, and microwave parameters (irradiation power and time), were optimized. The method simultaneously accomplishes the isolation, extraction and concentration of the essential oils. Compared to the conventional steam distillation (SD) method, which could only recover 35 compounds, MD-SPME led to the separation and identification of 53 compounds in the essential oils of Alpinia oxyphylla Miq. fruits. The intra-day and inter-day relative standard deviation (RSD) values of the MD-SPME-GC-MS method are all less than 8%, which shows that it has satisfactory precision. The MD-SPME-GC-MS method developed in this study is simple, rapid and solvent-free, and it shows promise for routine analysis of essential oils in fruits of Alpinia oxyphylla Miq. and, potentially, other TCMs.

A facile approach was used to prepare Fe3O4–graphene oxide (Fe3O4–GO) nanocomposites, and the application of these nanocomposites was investigated in the magnetic solid-phase extraction (MSPE) coupled with high-performance liquid chromatography with diode-array detection (HPLC-DAD) of three sulfonamides (SAs) from water samples. The Fe3O4–GO nanocomposites possess the advantages of both GO and Fe3O4. The Fe3O4–GO nanocomposites were characterized by scanning electron microscopy and vibrating-sample magnetometry. Sulfadiazine (SDZ), sulfadimidine (SDD) and sulfathiazole (STZ) were selected as target analytes to validate the extraction performance of the Fe3O4–GO nanocomposites as a MSPE adsorbent. The results indicated that the limits of detection of these sulfonamides were in the range of 0.05–0.10 μg mL−1, that the recoveries ranged between 67.4% and 119.9%, and that the linearity (R2 > 0.9900) and precision (between 0.04% and 9.03%) were good. The developed method can be used to determine and monitor SA residues in environmental water samples.

The first airborne comparison of N2O5 measurements over the UK using a CIMS and BBCEAS during the RONOCO campaign by Michael Le Breton; Asan Bacak; Jennifer B. A. Muller; Thomas J. Bannan; Oliver Kennedy; Bin Ouyang; Ping Xiao; Stéphane J.-B. Bauguitte; Dudley E. Shallcross; Roderic L. Jones; Mark J. S. Daniels; Stephen M. Ball; Carl J. Percival (9731-9743).
Dinitrogen pentoxide (N2O5) plays a central role in nighttime tropospheric chemistry as its formation and subsequent loss in sink processes limits the potential for tropospheric photochemistry to generate ozone the next day. Since accurate observational data for N2O5 are critical to examine our understanding of this chemistry, it is vital also to evaluate the capabilities of N2O5 measurement techniques through the co-deployment of the available instrumentation. This work compares measurements of N2O5 from two aircraft instruments on board the Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 aircraft during the Role of Nighttime Chemistry in Controlling the Oxidising Capacity of the Atmosphere (RONOCO) measurement campaigns over the United Kingdom in 2010 and 2011. A chemical ionisation mass spectrometer (CIMS), deployed for the first time for ambient N2O5 detection during RONOCO, measured N2O5 directly using I ionisation chemistry and an aircraft-based broadband cavity enhanced absorption spectrometer (BBCEAS), developed specifically for RONOCO, measured N2O5 by thermally dissociating N2O5 and quantifying the resultant NO3 spectroscopically within a high finesse optical cavity. N2O5 mixing ratios were simultaneously measured at 1 second time resolution (1 Hz) by the two instruments for 8 flights during RONOCO. The sensitivity for the CIMS instrument was 52 ion counts per pptv with a limit of detection of 7.4 pptv for 1 Hz measurements. BBCEAS, a proven technique for N2O5 measurement, had a limit of detection of 2 pptv. Comparison of the observed N2O5 mixing ratios show excellent agreement between the CIMS and BBCEAS methods for the whole dataset, as indicated by the square of the linear correlation coefficient, R2 = 0.89. Even stronger correlations (R2 values up to 0.98) were found for individual flights. Altitudinal profiles of N2O5 obtained by CIMS and BBCEAS also showed close agreement (R2 = 0.93). Similarly, N2O5 mixing ratios from both instruments were greatest within pollution plumes and were strongly positively correlated with the NO2 concentrations. The transition from day to nighttime chemistry was observed during a dusk-to-dawn flight during the summer 2011 RONOCO campaign: the CIMS and BBCEAS instruments simultaneously detected the increasing N2O5 concentrations after sunset. The performance of the CIMS and BBCEAS techniques demonstrated in the RONOCO dataset illustrate the benefits that accurate, high-frequency, aircraft-based measurements have for improving understanding the nighttime chemistry of N2O5.

Monitoring the metabolic response to nanoencapsulated silibinin treatment in DMBA-induced oral carcinogenesis using endogenous fluorescence by M. Gohulkumar; Shaiju S. Nazeer; Ramapurath S. Jayasree; K. Gurushankar; N. Krishnakumar (9744-9753).
Autofluorescence spectroscopy is a very sensitive tool for detecting early metabolic response after cancer treatment. The present work aims to investigate the chemopreventive effect of the prepared silibinin-loaded nanoparticles (SILNPs) relative to the efficacy of free silibinin (SIL) for monitoring the changes in the endogenous fluorophore emission and to quantify the metabolic changes in the redox state during 7,12-dimethylbenz[a]anthracene (DMBA) induced hamster buccal pouch (HBP) carcinogenesis using autofluorescence spectroscopy. Significant differences in the autofluorescence spectral signatures between the control and the experimental animals have been noticed under the excitation wavelength at 320 nm with emission ranging from 350–550 nm. The tumor tissues are characterized by a decrease in the emission of collagen, nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) compared to the control tissues. Further, the optical oxidation–reduction (redox) ratio is a measure of cellular metabolism and can be determined by the relative change in the fluorescence emission intensity of NADH and FAD. The optical redox ratio will provide sufficient information on metabolic changes associated with tumor transformation. The results revealed that a significant decrease in the optical redox ratio is observed in DMBA-induced tumor tissues, which indicates increased metabolic activity compared to the control tissues. Moreover, an oral administration of SIL and its nanoparticulates restored the status of endogenous fluorophore emission and led to a higher redox ratio in the buccal mucosa of DMBA-painted animals. On a comparative basis, treatment with nanoparticulate silibinin was found to be more effective than free silibinin for reducing the formation of squamous cell carcinoma and improving the status of endogenous fluorophore emission to a near normal range in DMBA-induced hamster buccal pouch carcinogenesis. Furthermore, the diagnostic algorithms based on principal component analysis followed by linear discriminant analysis (PC–LDA) achieved an overall diagnostic sensitivity of 96.46% and specificity of 93.64% for separating the control from the experimental groups. The results of this study further suggest that the fluorescence spectroscopic technique in conjunction with PC–LDA has a potential for rapid and sensitive detection of specific metabolic alteration and changes in the endogenous fluorophores in response to anti-cancer drug treatments.

Encapsulation of few cells into monodisperse picolitre droplets is an extremely critical step in the process of the droplet based single cell analysis. This paper presents a novel approach, not based on micro-fluidic chips fabricated by standard soft lithography technique, for encapsulating cells into droplets actuated by microfluidic pulse inertia force. The principle of the encapsulating process is to actuate a hollow PZT stack by a signal generator and a voltage amplification to provide an enough pulse inertia force for a tapered glass capillary and the cell suspension inside to eject droplets in mineral oil and a certain number of the cells will be randomly encapsulated in monodisperse picolitre droplets. The tapered glass capillary was fabricated by a glass heating process without complicated microfabrication technology. Therefore, it has the advantages of good chemical resistance, low friction, easy to manufacture and low cost. The minimum size of the spherical cell droplets that can be reached is 20 μm in diameter and about 4 picolitres in volume. The percentage of the droplets with single HL60 cell can reach 42% when the droplet size is 40 μm and the concentration of the cell suspension is 1 × 108 cells per milliliter since the alternate changed pulse inertia force can make the cells well dispersed in the tapered capillary. The percentage of viable cells that can be reached is 82% as determined by trypan blue staining, when the cell droplet size is 120 μm. The experiment results present a novel strategy for droplet-based single cell analysis.

Facile and controllable synthesis of Prussian blue nanocubes on TiO2–graphene composite nanosheets for nonenzymatic detection of hydrogen peroxide by Yanli Zhang; Jinling Xie; Shixiu Xiao; Zhongming Yang; Pengfei Pang; Wei Bai; Yuntao Gao (9761-9768).
A novel nonenzymatic sensor for hydrogen peroxide (H2O2) is developed based on a Nafion/Prussian blue/TiO2–graphene nanocomposite (Nafion/PB/TiO2–GR). The PB/TiO2–GR composite was prepared by the electrodeposition of PB nanocubes on the surface of TiO2–GR composite nanosheets and Nafion was used as a stabilizer. The Nafion/PB/TiO2–GR composite modified glassy carbon electrode (Nafion/PB/TiO2–GR/GCE) shows good electrocatalytic activity in the reduction of H2O2 and is used as an amperometric sensor. The sensor exhibits a linear response for H2O2 over concentrations ranging from 40 nM to 2 mM with a high sensitivity of 480.97 μA mM−1 cm−2 and a low detection limit (S/N = 3) of 8.6 nM. Additionally, the sensor exhibits long-term stability, good reproducibility and anti-interference. This study provides a new kind of nanocomposite modified electrode for electrochemical sensors.

Determination of polyphenols in the pear pulp matrix by solvent extraction and liquid chromatography with UV-Vis detection by Maria Raja; Joel Hernández-Revelles; Santiago Hernández-Cassou; Javier Saurina (9769-9776).
A new analytical method for the determination of polyphenolic compounds in pear pulp was developed here. The procedure consisted of solvent extraction for the recovery of analytes and further quantification by reversed-phase high-performance liquid chromatography with multidetection by UV-Vis molecular absorption spectroscopy. Preliminary studies were focused on establishing a straightforward extraction procedure for soluble compounds using organic and hydro-organic media. Dimethylsulfoxide was selected as the most efficient extraction solvent for the diverse polyphenol families. The chromatographic separation relied on a methanol gradient which was optimized by experimental design. Figures of merit were established under the selected experimental conditions using synthetic standards and pear extracts. In general, repeatabilities of peak areas were better than 3%, detection limits were in the order of magnitude of 0.1 mg L−1 and quantitative recoveries were about 100%. The method was applied to analyze commercial pears of various origins with chlorogenic, neochlorogenic and gallic acids, arbutin and catechin being some of the most abundant compounds. Differences in the polyphenol composition among pear varieties were found to be relevant. As a result, such compounds may result in potential descriptors of varietal characteristics.

A novel procedure is presented for the speciation of Cr(iii)/Cr(vi) involving directly suspended single droplet microextraction combined with electrothermal atomic absorption spectrometry. In this method, Cr(iii) can be extracted with 1-decanol at pH 6.0 due to the formation of a hydrophobic complex, Cr(iii)-8-hydroxyquinoline (8-HQ), whereas Cr(vi) remains in the aqueous solution. The Cr(vi) concentration was calculated by subtracting the concentration of Cr(iii) from the total chromium concentration after reducing Cr(vi) to Cr(iii) by addition of hydroxylamine hydrochloride. Different factors affecting the extraction of Cr(iii), such as pH, 8-HQ concentration, stirring rate, extraction temperature and time, and interfering ions, were schematically evaluated. Under the selected conditions, the limit of detection for Cr(iii) was 0.03 ng mL−1 with a relative standard deviation of 4.7% (C = 1.0 ng mL−1, n = 5). The calibration curve was highly linear for the Cr(iii) concentration range of 0.10–2.0 ng mL−1. The proposed method was validated against certified reference materials of environmental water (GSBZ50027-94, GBW(E)080642), and successfully applied in the speciation of chromium in well and tap water samples.

Classification of vinegar with different marked ages using olfactory sensors and gustatory sensors by Quansheng Chen; Cuicui Sun; Qin Ouyang; Aiping Liu; Huanhuan Li; Jiewen Zhao (9783-9790).
An improved classification of vinegar with different marked ages is presented using a combination of gustatory sensors and olfactory sensors. Herein, the gustatory sensor system is developed using four electrodes (gold, copper, platinum and glassy carbon) in a standard three-electrode configuration, and the olfactory system is developed based on a colorimetric sensor array. Initially, the data obtained from the two sensor systems were analyzed separately. Then, the potential of the combination of the two sensor systems for classification is investigated. Principal component analysis (PCA) and linear discriminant analysis (LDA), as two classification tools, are used for data classification. The results show that the capability of discrimination of the combined system is superior to that obtained with the two sensor systems separately, and eventually LDA achieved 100% classification rate by cross-validation. This work indicates that the combination of gustatory sensor systems and olfactory sensor systems can be a useful tool for the classification of vinegar with different marked ages.

In this work, a novel type of core–shell molecularly imprinted magnetic nanoparticles was synthesized and coupled with HPLC for the selective extraction and detection of 17β-estradiol (E2) in lake water samples. The synthesis procedure combined a surface imprinting technique and a facile sol–gel strategy. The morphology, structure, and magnetic properties of the obtained products were characterized by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and vibrating sample magnetometer. The adsorption properties of the prepared polymers were investigated by equilibrium rebinding, dynamic adsorption, and selective recognition experiments. The resultant imprinted nanomaterials exhibit not only good dispersibility, stable crystalline structure, and satisfactory super-paramagnetic properties, but also fast kinetics, high capacity (16.87 mg g−1), and favorable selectivity. In addition, the as-synthesized polymers show good reproducibility and could be used for at least six cycles of adsorption–desorption without obvious deterioration. The feasibility of the developed method using the obtained imprinted polymers as a SPE extractant coupled with HPLC for the selective isolation and determination of E2 from real water samples was demonstrated. The recovery of E2 in a lake water sample ranged from 94.2 to 98.3% with the relative standard deviation less than 4.3%. The combined method would greatly improve the sensitivity and expand the practicability of HPLC.

Poly-γ-glutamic acid modified magnetic nanoparticles for fast solid phase extraction of trace amounts of Cu(ii) and Pb(ii) by Honglun Yuan; Xuetuan Wei; Zhaorui Zeng; Daikai Yang; Shouwen Chen (9800-9806).
In the present study, poly-γ-glutamic acid (γ-PGA) was applied to functionalize the silica-coated magnetic nanoparticles for solid-phase extraction of Cu(ii) and Pb(ii). Firstly, the silica-coated magnetic nanoparticles were modified with γ-PGA using the sol–gel method. Fourier transform infrared (FT-IR) spectrum analysis confirmed that γ-PGA was bound onto the magnetic nanoparticles, and the Transmission electron microscope (TEM) image showed that as-prepared nanoparticles were of typical core–shell structure with an average size of 12.5 nm. Secondly, the γ-PGA modified magnetic nanoparticles were used in solid-phase extraction of Cu(ii) and Pb(ii). Various parameters including the pH, eluent concentration, eluent volume, extraction time, and sample volume, and potentially interfering ions were investigated to establish the optimal experimental conditions. Under the optimal conditions, the limits of detection (LOD) for Cu(ii) and Pb(ii) were 0.46 and 1.43 μg L−1 respectively, and the enrichment factors reached 166 and 133, as well as the low relative standard deviations (RSDs, n = 7, c = 50 μg L−1) of 2.48% and 7.42% for Cu(ii) and Pb(ii), respectively. Moreover, the as-synthesized sorbent was efficient for extraction of Cu(ii) and Pb(ii) from different practical water samples. This study provided a fast, simple and selective heavy metal analysis method using solid phase extraction coupled with flame atomic absorption spectrometry.

Di-(2-ethylhexyl)phthalate (DEHP) is one of the long-chain or high-molecular-weight compounds of the phthalic acid diester (PAE) family, which is the most commonly used plasticizer and additive. However, DEHP may cause birth defects, sexual dysfunction, even cancers, possibly heart disease, etc. In order to detect DEHP with high sensitivity and specificity, an indirect competitive biotin–streptavidin enzyme-linked immunosorbent assay (BA-ELISA) has been established in this study. A specific polyclonal antibody (pAb-DEHP) targeting DEHP was obtained first, and the procedures of BA-ELISA were optimized for the determination of DEHP in beverages. Under optimal conditions, a good linearity was achieved within a range of 0.021 to 12.948 μg L−1. The limit of detection (IC10) was 0.0074 μg L−1 and the median inhibitory concentration (IC50) was 0.526 μg L−1. The BA-ELISA was highly selective, with low cross-reactivity values with DEHP analogues (lower than 7%). Finally, the assay was successfully used to detect DEHP in beverages; the concentrations of DEHP in the samples ranged from 1.18 μg L−1 to 40.68 μg L−1. Satisfactory recoveries (89.07–109.33%) and coefficient of variation (CV) values (5.97% to 10.68%) were obtained, which further confirmed that this proposed BA-ELISA immunoassay is sensitive, rapid and accurate for monitoring DEHP in the environment.

Colorimetric determination of hydrogen peroxide by morphological decomposition of silver nanoprisms coupled with chromaticity analysis by Kritchapon Nitinaivinij; Tewarak Parnklang; Chuchaat Thammacharoen; Sanong Ekgasit; Kanet Wongravee (9816-9824).
A novel colorimetric method with image colour analysis for highly sensitive and accurate detection of hydrogen peroxide using starch-stabilized silver nanoprisms (AgNPrs) is proposed. AgNPrs were morphologically decomposed by a low concentration of hydrogen peroxide revealed by UV-visible absorption spectroscopy and transmission electron microscopy (TEM). The morphological changes of AgNPrs led to an appreciable colour change in the AgNPr solution from red to orange, and finally yellow. A good linear relationship between the wavelength shift of AgNPrs and the H2O2 concentration can be obtained. The solution phase detection of H2O2 by the direct morphological change can be accomplished without any surface modification of AgNPrs. In addition to the conventional determination of the H2O2 concentration utilizing spectroscopic data, a new and simple colorimetric strategy based on the chromaticity analysis of AgNPr solution was demonstrated. The strategy can be employed not only for visual detection of H2O2 by the naked eye but also for reliable and convenient methods for quantification of H2O2. The hydrogen peroxide concentration at 1.57 μM can be recognized by naked-eye observation with good accuracy, stability and reproducibility. Furthermore, the proposed protocol can be applied to determine the glucose concentration through the glucose-oxidase system. A good linearity between the red chromaticity of the solution colour and the glucose concentrations was observed. The new colorimetric determination of hydrogen peroxide utilizing digital image analysis on colour changes from AgNPr shape decomposition will open up an alternative method for simple, rapid and reliable detection of hydrogen peroxide and can realize its future applications in biochemical analysis or clinical diagnosis.

A fluorophore dyad (L) containing rhodamine B and naphthalimide units linked through CN was constructed as a ratiometric probe for Cu2+. The selective fluorescent response of the probe L to Cu2+ was triggered by a Cu2+ induced ring-opening process of the rhodamine B spirolactam, which was based on an intramolecular fluorescence resonance energy transfer (FRET) mechanism from naphthalimide to rhodamine B. The system exhibited high selectivity for Cu2+ as compared to other tested metal ions and anions, and signaled the binding event through occurrence of FRET mediated emission at 580 nm of the rhodamine chromophore with enhancement in the fluorescence intensity, concurrently, the featured emission of the naphthalimide donor at around 525 nm was nearly completely quenched. Furthermore, it has been used for ratiometric imaging of Cu2+ in living cells with satisfying results.

Currently, a key problem in near-infrared (NIR) non-invasive blood glucose sensing is that the influence of the background changes during measurements, which restricts the effective extraction of unique glucose information. As the influence of the background can only be reduced by various correction techniques, standard sample correction and reference beam designs are investigated in this paper. First, the basic principles and preconditions for the background correction of single-beam measurements with reference correction and double-beam measurements with double detectors are analyzed. Second, the signal-to-noise ratio (SNR) in different measurement modes is evaluated. Third, single-day and multi-day experiments are conducted on aqueous glucose solution. The results are as follows: (1) short time interval between measurements of the sample and reference is the prerequisite for reference correction measurement with single-beam. The double-beam measurement has no special requirement for the SNR and the sampling time interval. (2) The double-beam design is more effective at eliminating the time-dependent variations. The SNR of the single-beam measurement can be improved by correcting the reference sample, which is also verified by the 2D correlation spectroscopy analysis under the perturbation of time. (3) The predictive ability of the partial least squares (PLS) model based on double-beam measurement is the best for both single-day experiments and multi-day experiments, which is consistent with results of the SNR test. Both the reference sample correction and the reference beam design can effectively reduce the light source drift and the double-beam design is more appropriate for multi-day or long-term experiments.

Hydrogen cyanide is a well-known toxic component in cigarette smoke. Accurate determination of hydrogen cyanide is of great significance to assess the risk of cigarettes to public health. In the conventional method for determination of hydrogen cyanide in cigarette smoke, an alkaline solution is used to collect hydrogen cyanide. In our study, nitrogen oxides in the smoke were found to dissolve in the alkaline solution, and they could react with the alkaline solution to produce nitrates and nitrites which could further react with cyanide to result in underestimating the yield of hydrogen cyanide. An improved method for the determination of hydrogen cyanide was developed in our laboratory to solve the problem, in which the hydrogen cyanide from mainstream cigarette smoke was collected using a Cambridge filter pad (CFP) treated with an ethanol–water solution of sodium hydroxide and detected by a continuous flow analyzer based on a coloring system with isonicotinic acid and 1,3-dimethylbarbituric acid. The collection efficiency of hydrogen cyanide for this method was significantly improved compared with conventional methods of trapping hydrogen cyanide using an alkaline solution. Furthermore, the collection and sample preparation process was simpler, with higher stability of the collected hydrogen cyanide. The limit of detection (LOD) and limit of quantification (LOQ) for the determination of hydrogen cyanide were less than 1.08 × 10−2 mg L−1 and 3.74 × 10−2 mg L−1, respectively. The improved method achieved excellent recoveries in the range 99.13–100.37% for mainstream smoke detection and 96.41–101.96% for sidestream smoke detection. Excellent precision for hydrogen cyanide determination was obtained, with the intra-assay and inter-assay relative standard deviation (RSD%) for mainstream smoke detection being 3.58% and 4.44%, respectively, and the intra-assay and inter-assay RSD% for sidestream smoke detection being 1.48% and 2.28%, respectively. The method developed is reliable and suitable for routine analysis of hydrogen cyanide in both mainstream and sidestream cigarette smoke.

An electrolyte cathode discharge atomic emission spectrometric (ELCAD-AES) method has been reported for the determination of cadmium in Zircaloys. Formic and acetic acids are examined to improve the sensitivity of ELCAD-AES for cadmium determination. The sensitivity of ELCAD-AES is improved 2-fold with 20% (v/v) formic acid. With 20% (v/v) formic acid, the improved detection limit of ELCAD-AES for cadmium is found to be 2 ng mL−1. A previously reported matrix separation procedure using ammonium pyrrolidine dithiocarbamate (APDC) and methylisobutylketone (MIBK) for the extraction of Cd from Zirconium matrices has been optimised for ELCAD-AES analysis of cadmium. This procedure is found to be useful for the quantitative determination of cadmium in Zircaloys by ELCAD-AES. The precision expressed as a percentage relative standard deviation of the signals of multiple analyses (N = 5) of ELCAD-AES method using the above matrix separation procedure has been found to be 10–15% for trace Cd. This ELCAD-AES method is validated with the certified values of Zircaloy CRM and the glow discharge quadrupole mass spectrometry (GD-QMS) values of Zircaloy samples.

Back cover (9857-9858).