Analytica Chimica Acta (v.706, #1)
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Image analysis for maintenance of coating quality in nickel electroplating baths – Real time control by M. Vidal; J.M. Amigo; R. Bro; F. van den Berg; M. Ostra; C. Ubide (1-7).
Display Omitted► This manuscript presents a complete methodology for online process control of the electroplating processes. ► The methodology uses flat-bed scanners for collecting pictures of the electroplated flat surfaces with nickel. ► Dedicated software has been developed for making the obtained results accessible to process operators. ► The statistical parameters of control are the mean and the standard deviation of the colour in the whole surface. ► The methodology can possibly be extended to other similar metal electroplating baths.The aim of this paper is to show how it is possible to extract analytical information from images acquired with a flatbed scanner and make use of this information for real time control of a nickel plating process. Digital images of plated steel sheets in a nickel bath are used to follow the process under degradation of specific additives. Dedicated software has been developed for making the obtained results accessible to process operators. This includes obtaining the RGB image, to select the red channel data exclusively, to calculate the histogram of the red channel data and to calculate the mean colour value (MCV) and the standard deviation of the red channel data. MCV is then used by the software to determine the concentration of the additives Supreme Plus Brightner (SPB) and SA-1 (for confidentiality reasons, the chemical contents cannot be further detailed) present in the bath (these two additives degrade and their concentration changes during the process). Finally, the software informs the operator when the bath is generating unsuitable quality plating and suggests the amount of SPB and SA-1 to be added in order to recover the original plating quality.
Keywords: Flatbed scanner; Image analysis; Nickel electrodeposition; Additives determination; “Real control” software; Process analysis;
Localized surface plasmon resonance: Nanostructures, bioassays and biosensing—A review by Eleonora Petryayeva; Ulrich J. Krull (8-24).
Display Omitted► An overview of fundamental physical theory is provided to explain LSPR. ► A survey is provided of structures that can support LSPR. ► Examples of applications of LSPR have emphasis on determination of biochemical and biological targets.Localized surface plasmon resonance (LSPR) is an optical phenomena generated by light when it interacts with conductive nanoparticles (NPs) that are smaller than the incident wavelength. As in surface plasmon resonance, the electric field of incident light can be deposited to collectively excite electrons of a conduction band, with the result being coherent localized plasmon oscillations with a resonant frequency that strongly depends on the composition, size, geometry, dielectric environment and separation distance of NPs. This review serves to describe the physical theory of LSPR formation at the surface of nanostructures, and the potential for this optical technology to serve as a basis for the development bioassays and biosensing of high sensitivity. The benefits and challenges associated with various experimental designs of nanoparticles and detection systems, as well as creative approaches that have been developed to improve sensitivity and limits of detection are highlighted using examples from the literature.
Keywords: Localized surface plasmon resonance; Wavelength shift; Surface enhanced Raman spectroscopy; Metal enhanced fluorescence; Biosensor; Metal nanoparticle;
A review of opportunities for electrospun nanofibers in analytical chemistry by Samuel Chigome; Nelson Torto (25-36).
Display Omitted► Electrospun nanofiber based separation systems. ► Electrospun nanofiber based detection systems. ► Electrospun nanofiber based non invasive colorimetric analytical devices.Challenges associated with analyte and matrix complexities and the ever increasing pressure from all sectors of industry for alternative analytical devices, have necessitated the development and application of new materials in analytical chemistry. To date, nanomaterials have emerged as having excellent properties for analytical chemistry applications mainly due to their large surface area to volume ratio and the availability of a wide variety of chemical and morphological modification methods. Of the available nanofibrous material fabrication methods, electrospinning has emerged as the most versatile. It is the aim of this contribution to highlight some of the recent developments that harness the great potential shown by electrospun nanofibers for application in analytical chemistry. The review discusses the use of electrospun nanofibers as a platform for low resolution separation or as a chromatographic sorbent bed for high resolution separation. It concludes by discussing the applications of electrospun nanofibers in detection systems with a specific focus on the development of simple electrospun nanofiber based colorimetric probes.
Keywords: Electrospinning; Nanofibers; Efficiency; Separation; Detection;
Recent advances in applications of single-drop microextraction: A review by Archana Jain; Krishna K. Verma (37-65).
Display Omitted► The applications of single-drop microextraction reported during 1996 to mid 2011 have been reviewed. ► The technique produces extract in a much simpler manner and gives high sensitivity since the whole extract is used for analysis. ► Analysis of extract by nearly all types of instrumental methods of analysis is possible. ► Easy chemical manipulation of analytes is feasible either in the microdrop of solvent or in the sample solution.During the past fifteen years since its introduction, single-drop microextraction has witnessed incessant growth in the range of applications of samples preparation for trace organic and inorganic analysis. This was mainly due to the array of modes that are available to accomplish extraction in harmony with the nature of analytes, and to use the extract directly for analysis by diverse instrumental methods. Whilst engineering of novel sorbent materials has expanded the sample capabilities of rival method of solid-phase microextraction, the single-drop microextraction – irrespective of the mode of extraction – uses common equipment found in analytical laboratories sans any modification, and in a much economic way. The recent innovations made in the field, as highlighted in this review article in the backdrop of historical developments, are due to the freedom in operational conditions and practicability to exploit chemical principals for optimum extraction and sensitive determination of analytes. Literature published till July 2011 has been covered.
Keywords: Single-drop microextraction; Solvent microextraction; Liquid-phase microextraction; Liquid–liquid microextraction;
Matrix effects in inductively coupled plasma mass spectrometry: A review by Christian Agatemor; Diane Beauchemin (66-83).
.Display Omitted► ICPMS applications often require a combination of methods to cope with matrix effects. ► Matrix, analyte, concentrations and ICPMS operating conditions affect matrix effects. ► Because of this complexity, there is no single way of eliminating matrix effects. ► The sample introduction system can be a significant source of matrix effects. ► Employing robust plasma conditions is the simplest way of reducing matrix effects.Fundamental research on non-spectroscopic interferences, also known as matrix effects, in inductively coupled plasma (ICP) mass spectrometry with sample introduction using nebulization is critically and exclusively examined in this review, starting with fundamental processes that may be a source of matrix effects during sample introduction, ion generation in the ICP, ion extraction through the interface, and ion transport through the ion optics to the detector. Various methods for attenuating matrix effects are then reviewed and illustrated with some examples. Instead of exhaustively reviewing the literature, representative references are used to comprehensively describe the main issues, several of which are also common to ICP optical emission spectrometry.
Keywords: Inductively coupled plasma mass spectrometry; Matrix effects; Non-spectroscopic interferences; Robust plasma;
Determination of ultratrace levels of dissolved metals in seawater by reaction cell inductively coupled plasma mass spectrometry after ammonia induced magnesium hydroxide coprecipitation by Francisco Ardini; Emanuele Magi; Marco Grotti (84-88).
Accurate quantification of trace elements in open ocean waters was obtained by combining the Mg(OH)2 coprecipitation procedure with quadrupole ICP-MS and using the dynamic reaction cell to remove the residual interferences.Display Omitted► A new method for the determination of ultratrace amounts of Cr, Fe, Mn, Pb and Zn in seawater has been developed. ► Polyatomic interferences have been successfully reduced by the application of the dynamic reaction cell. ► Blanks, detection limits and accuracy were adequate for reliable determination of trace elements in open-ocean waters. ► Analytical figures were better than most of quadrupole ICP-MS methods, approaching those of ICP-SFMS.A method for the determination of ultratrace amounts of Cr, Fe, Mn, Pb and Zn in seawater has been developed. It combined the low-blank magnesium hydroxide coprecipitation procedure with quadrupole inductively coupled plasma mass spectrometry and used the dynamic reaction cell technique to resolve the polyatomic interferences arising from the residual matrix, the solvent and plasma gases. Detection limits (3σ B, n = 10) for Cr, Fe, Mn, Pb and Zn were 0.02, 0.10, 0.01, 0.002 and 0.19 nM, respectively, using 50 mL of seawater sample. The accuracy of the analytical procedure was verified by the analysis of the seawater reference materials CASS-4, NASS-5, SAFe D2 and SAFe S. The analytical precision ranged from 3% to 16% (n = 6), with a sample throughput of about 6 samples h−1.
Keywords: Inductively coupled plasma mass spectrometry; Polyatomic interferences; Matrix effects; Dynamic reaction cell; Trace elements; Seawater;
An improved method for determination of lanthanoids in environmental samples by inductively coupled plasma mass spectrometry with high matrix introduction system by Valbona Celo; Ewa Dabek-Zlotorzynska; Jiujiang Zhao; Irina Okonskaia; David Bowman (89-96).
Display Omitted► High matrix introduction system decreased spectral interferences. ► Oxides and hydroxide yields were less than 0.5% and IDLs below 8 ng L−1. ► Evaporation of excess HF in presence of HCl improved dissolution of lanthanoids. ► Recoveries of lanthanoids after digestion with HNO3/H2O2/HCl/HF were 76–115%. ► The obtained limits of detection ranged from 0.1 to 6 μg kg−1.The capability of ICP-MS equipped with the high matrix introduction system (HMI) for accurate analysis of lanthanoids in environmental samples was investigated. Compared to the conventional operation, the amounts of oxide and hydroxide molecular species formed in the plasma were reduced by up to 5 times. The relative yields of oxides did not exceed 0.02% for BaO+ species and were as low as 0.3% for lanthanoids with the highest oxide-formation rates (LaO+, CeO+, PrO+ and NdO+). Hydroxide formation was less than 0.02% when HMI system was used. In addition, two digestion procedures were evaluated by the analysis of standard reference materials (SRMs) of different matrices. The digestion efficiency and limits of detection (LOD) were improved when samples were digested with a mixture of HNO3/H2O2/HCl/HF, and HF was removed by evaporation in presence of concentrated HCl. Using this procedure and HMI-ICP-MS analysis, LOD ranged from 0.1 μg kg−1 to 6 μg kg−1. Recoveries ranged from 85 to 115% for La to Ho and from 75 to 85% for the other lanthanoids. Relative standard deviations for replicate analysis of SRMs were less than 10%.
Keywords: Lanthanoids; Inductively coupled plasma mass spectrometry (ICP-MS); High matrix introduction system (HMI); Microwave digestion; Environmental samples;
A novel kernel Fisher discriminant analysis: Constructing informative kernel by decision tree ensemble for metabolomics data analysis by Dong-Sheng Cao; Mao-Mao Zeng; Lun-Zhao Yi; Bing Wang; Qing-Song Xu; Qian-Nan Hu; Liang-Xiao Zhang; Hong-Mei Lu; Yi-Zeng Liang (97-104).
Display Omitted► We developed a novel KFDA algorithm by constructing an informative kernel based on decision tree ensemble. ► The kernel can encode the similarities of metabolomics samples between biomarkers space. ► KFDA can also deal with nonlinear relationship in the metabolomics data by such a kernel. ► Two real datasets together with a simulated data demonstrated the performance of KFDA.Large amounts of data from high-throughput metabolomics experiments become commonly more and more complex, which brings an enormous amount of challenges to existing statistical modeling. Thus there is a need to develop statistically efficient approach for mining the underlying metabolite information contained by metabolomics data under investigation. In the work, we developed a novel kernel Fisher discriminant analysis (KFDA) algorithm by constructing an informative kernel based on decision tree ensemble. The constructed kernel can effectively encode the similarities of metabolomics samples between informative metabolites/biomarkers in specific parts of the measurement space. Simultaneously, informative metabolites or potential biomarkers can be successfully discovered by variable importance ranking in the process of building kernel. Moreover, KFDA can also deal with nonlinear relationship in the metabolomics data by such a kernel to some extent. Finally, two real metabolomics datasets together with a simulated data were used to demonstrate the performance of the proposed approach through the comparison of different approaches.
Keywords: Metabolomics; Kernel methods; Fisher discriminant analysis (FDA); Biomarker discovery; Decision tree; Classification and regression tree (CART);
In vivo noninvasive detection of chlorophyll distribution in cucumber (Cucumis sativus) leaves by indices based on hyperspectral imaging by Zou Xiaobo; Shi Jiyong; Hao Limin; Zhao Jiewen; Mao Hanpin; Chen Zhenwei; Li Yanxiao; Mel Holmes (105-112).
Display Omitted► Hyperspectral imaging for noninvasive chlorophyll estimation and distribution in cucumber leaves. ► Simple sixty optical signature or indices for chlorophyll estimation. ► Optimum index showed its robustness for an independent validation set. ► Spatial localization of chlorophyll accumulation could be mapped in vivo. The objective of this study was to investigate the spectral behavior of the relationship between reflectance and chlorophyll content and to develop a technique for non-destructive chlorophyll estimation and distribution in leaves using hyperspectral imaging. The hyperspectral imaging data cube of cucumber (Cucumis sativus) leaves in the range of 450–850 nm was investigated and preprocessed. Sixty optical signatures or indices as a function of the associated reflectance (R λ ) at the special wavelength (λ) nm which proposed in the literatures were used to predict the total chlorophyll content in cucumber leaves. Finally, R 710/R 760, (R 780 − R 710)/(R 780 − R 680), (R 750 − R 705)/(R 750 + R 705), (R 680 − R 430)/(R 680 + R 430), R 860/(R 550 × R 708), (R 695−705)−1 − (R 750−800)−1, and REP-LEM (a index based on red edge position and estimated with a linear extrapolation method) were identified as optimum indices. Red-edge waveband (680–780 nm) appeared in all these optimum indices, indicating the importance of REP (red edge position) in chlorophyll estimation. When (R 695−705)−1 − (R 750−800)−1, the best index was applied to an independent validation set, chlorophyll content (r = 0.8286) were reasonably well predicted, indicating model robustness. Depending on the sample, this technique enables to identify and characterize the relative content of various chlorophyll that distribution in the cucumber leaves. The map shows a relatively low level of chlorophyll at margins. Higher level can be noticed in the regions along the main veins and in some areas exhibiting dark green tissue. Our results indicate that hyperspectral imaging has considerable promise for predicting pigments in leaves and, the pigments can be detected in situ in living plant samples non-destructively.
Keywords: Hyperspectral imaging; Index; Leaf chlorophyll content; Non-destructive estimation; Cucumber leaf;
Analysis of pharmaceutical pellets: An approach using near-infrared chemical imaging by Guilherme P. Sabin; Márcia C. Breitkreitz; André M. de Souza; Patrícia da Fonseca; Lupercio Calefe; Mario Moffa; Ronei J. Poppi (113-119).
Display Omitted► Near-Infrared Chemical Imaging was used for pellets analysis. ► Distribution of the components throughout the coatings layers and core of the pellets was estimated. ► Classical Least Squares (CLS) was used for calculation of the concentration maps.Pharmaceutical pellets are spherical or nearly spherical multi-unit dosage forms designed to optimize pharmacokinetics and pharmacodynamics features of drug release. The distribution of the pharmaceutical ingredients in the layers and core is a very important parameter for appropriate drug release, especially for pellets manufactured by the process of layer gain. Physical aspects of the sample are normally evaluated by Scanning Electron Microscopy (SEM), but it is in many cases unsuitable to provide conclusive chemical information about the distribution of the pharmaceutical ingredients in both layers and core. On the other hand, methods based on spectroscopic imaging can be very promising for this purpose. In this work, a Near-Infrared Chemical Imaging (NIR-CI) method was developed and applied to the analysis of diclophenac sodium pellets. Since all the compounds present in the sample were known in advance, Classical Least Squares (CLS) was used for calculations. The results have shown that the method was capable of providing chemical information about the distribution of the active ingredient and excipients in the core and coating layers and therefore can be complementary to SEM for the pharmaceutical development of pellets.
Keywords: Pharmaceutical pellets; Chemical image; Near infrared; Chemometrics;
Development of an impedimetric immunosensor for the determination of 3-amino-2-oxazolidone residue in food samples by Gongjun Yang; Wenjie Jin; Liping Wu; Qianqian Wang; Hongxia Shao; Aijian Qin; Bing Yu; Dongming Li; Baoliang Cai (120-127).
Faradaic impendence spectra that the immunosensor incubated with different concentrations of AOZ in 0.1 M phosphate buffer solution (pH 7.5) and 0.1 M KNO3 containing 1.0 mM K3[Fe(CN)6]/K4[Fe(CN)6] (1:1 mixture).Display Omitted► A new method for AOZ detection was firstly reported based on immobilizing the self-made AOZ-McAb on the Au-SAMs by the impedimetric immunosensors. ► The proposed immunosensor exhibited high sensitivity, wide linear range, acceptable reproducibility and selectivity. It provided a simple method for direct detection of AOZ residue in food samples. ► The results were in good agreement with what was obtained by HPLC–MS/MS. Compared to HPLC–MS/MS, the proposed method can shorten the whole analysis time and simplify the sample's treatment.The use of furazolidone in food animals has been banned in European Union (EU) because of its carcinogenicity and mutagenicity on human health, but its continued misuse is widespread. Therefore, there is an urgent need for a simple, reliable, and rapid method for the detection of its marker residue, 3-amino-2-oxazolidinone (AOZ), in food products. In this regard, a sensitive and reliable electrochemical method was presented to detect AOZ based on a novel label-free electrochemical impedimetric immunosensor to address this need. The immobilization of monoclonal antibody against AOZ (denoted as AOZ-McAb) on the gold electrode was carried out through a stable acyl amino ester intermediate generated by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydrosuccinimide (NHS), which could condense antibodies on the self-assembled monolayer (SAM). The detection of AOZ was performed by measuring the relative change in charge transfer resistance before and after AOZ and AOZ-McAb immunoreaction by electrochemical impedance spectroscopy (EIS). Under the optimized conditions, the relative change in charge transfer resistance was proportional to the logarithmic value of AOZ concentrations in the range of 20.0 to 1.0 × 104 ng mL−1 (r = 0.9987). Moreover, the proposed immunosensor has a high selectivity to AOZ alone with no significant response to the metabolites of other nitrofuran antibiotics, such as 3-amino-5-morpholinomethyl-2-oxazolidinone (AMOZ), semicarbazide (SEM), and 1-aminohydantoin hydrochloride (AHD). This protocol has been applied to detect AOZ in food samples with satisfactory results.
Keywords: Immunosensor; Electrochemical impedance spectroscopy; 3-Amino-2-oxazolidone; Residue; Food;
Quantification of oxygenated volatile organic compounds in seawater by membrane inlet-proton transfer reaction/mass spectrometry by Rachael Beale; Peter S. Liss; Joanna L. Dixon; Philip D. Nightingale (128-134).
Display Omitted► We couple a membrane inlet to a proton transfer reaction mass spectrometer. ► We extract oxygenated volatile organic compounds from seawater. ► Method comparison to other techniques. ► Method optimisation and validation achieved with aqueous standards. ► Interference to acetone signal from propanal corrected by co-analysis using gas chromatography.The role of the ocean in the cycling of oxygenated volatile organic compounds (OVOCs) remains largely unanswered due to a paucity of datasets. We describe the method development of a membrane inlet-proton transfer reaction/mass spectrometer (MI-PTR/MS) as an efficient method of analysing methanol, acetaldehyde and acetone in seawater. Validation of the technique with water standards shows that the optimised responses are linear and reproducible. Limits of detection are 27 nM for methanol, 0.7 nM for acetaldehyde and 0.3 nM for acetone. Acetone and acetaldehyde concentrations generated by MI-PTR/MS are compared to a second, independent method based on purge and trap-gas chromatography/flame ionisation detection (P&T-GC/FID) and show excellent agreement. Chromatographic separation of isomeric species acetone and propanal permits correction to mass 59 signal generated by the PTR/MS and overcomes a known uncertainty in reporting acetone concentrations via mass spectrometry. A third bioassay technique using radiolabelled acetone further supported the result generated by this method. We present the development and optimisation of the MI-PTR/MS technique as a reliable and convenient tool for analysing seawater samples for these trace gases. We compare this method with other analytical techniques and discuss its potential use in improving the current understanding of the cycling of oceanic OVOCs.
Keywords: Oxygenated volatile organic compounds; Proton transfer reaction/mass spectrometry; Membrane inlet; Methanol; Acetaldehyde; Acetone;
Development and application of a polar coating for stir bar sorptive extraction of emerging pollutants from environmental water samples by D. Bratkowska; R.M. Marcé; P.A.G. Cormack; F. Borrull; N. Fontanals (135-142).
Display Omitted► We prepare a new polar monolithic coating for stir bar sorptive extraction (SBSE). ► The new coating is successfully apply for SBSE polar compounds. ► We develop an effective method to determine polar pollutants in water samples.In the present study, a stir bar coated with hydrophilic polymer based on poly(N-vinylpyrrolidone-co-divinylbenzene) was prepared for the sorptive extraction of polar compounds. The main parameters affecting the polymerisation of the coating were investigated.The new stir bar was applied successfully in stir bar sorptive extraction with liquid desorption followed by liquid chromatography–mass spectrometry in tandem with a triple quadrupole for the determination of a group of polar pharmaceuticals and personal care products (PPCPs) in environmental water matrices. Different variables affecting extraction and desorption such as agitation speed, temperature, ionic strength and extraction time were optimised. The results showed that the stir bar is able to enrich the selected analytes effectively.The developed method was applied to determine a group of PPCPs in different complex environmental samples, including river, effluent and influent waste water.
Keywords: Stir bar sorptive extraction (SBSE); Monolithic polar material; Pharmaceuticals and personal care products (PPCPs); Environmental water samples;
Streptavidin-functionalized capillary immune microreactor for highly efficient chemiluminescent immunoassay by Zhanjun Yang; Chen Zong; Huangxian Ju; Feng Yan (143-148).
Display Omitted► A novel capillary immune microreactor was proposed for highly efficient flow-through chemiluminescent immunoassay. ► The microreactor was prepared by functionalizing capillary inner wall with streptavidin for capture of biotinylated antibody. ► The proposed immunoassay method showed wide dynamic range, good reproducibility, stability and practicality. ► The microreactor was low-cost and disposable, and possessed several advantages over the conventional immunoreactors.A streptavidin functionalized capillary immune microreactor was designed for highly efficient flow-through chemiluminescent (CL) immunoassay. The functionalized capillary could be used as both a support for highly efficient immobilization of antibody and a flow cell for flow-through immunoassay. The functionalized inner wall and the capture process were characterized using scanning electron microscopy. Compared to conventional packed tube or thin-layer cell immunoreactor, the proposed microreactor showed remarkable properties such as lower cost, simpler fabrication, better practicality and wider dynamic range for fast CL immunoassay with good reproducibility and stability. Using α-fetoprotein as model analyte, the highly efficient CL flow-through immunoassay system showed a linear range of 3 orders of magnitude from 0.5 to 200 ng mL−1 and a low detection limit of 0.1 ng mL−1. The capillary immune microreactor could make up the shortcoming of conventional CL immunoreactors and provided a promising alternative for highly efficient flow-injection immunoassay.
Keywords: Immune microreactor; Capillary; Chemiluminescence; Immunoassay; Streptavidin; α-Fetoprotein;
Simultaneous determination of triazine herbicides in rice by high-performance liquid chromatography coupled with high resolution and high mass accuracy hybrid linear ion trap-orbitrap mass spectrometry by Ren-Xiang Mou; Ming-Xue Chen; Zhao-Yun Cao; Zhi-Wei Zhu (149-156).
The high-resolution extracted ion chromatograms of standard cyanazine in data dependent scan mode at the resolving powers of 15 000 (a) and 30 000 (b) in CID MS/MS scan.Display Omitted► The study reported an analytical method for triazine herbicides quantification. ► Analytes were quantified in rice matrix by LC LTQ-Orbitrap MS. ► The different resolution resulted a different scan data points. ► Exact precursor ion and exact product ion were monitored in the data dependent mode. ► Mass accuracies were similar between the matrix-matched and the pure-solution.A method was developed for the simultaneous determination of 10 triazine herbicides (cyanazine, simazine, simetryn, metribuzin, atrazine, ametryn, terbuthylazine, prometryn, terbutryn, and dimethametryn) in rice samples by high resolution and high mass accuracy hybrid linear ion trap-Orbitrap mass spectrometer. After extraction with acetonitrile and evaporation, the herbicides were redissolved in n-hexane and purified on a Florisil solid-phase extraction column. All compounds were separated within 12 min, producing more than 11 data points for each herbicide and high mass accuracy quantified ions which the mass errors of absolute value were less than 1.9 ppm in pure solution and 2.1 ppm in the matrix-matched standards solution. The method was validated in terms of the limits of detection and the limits of quantification. The linearity was satisfactory, with a correlation coefficient of >0.9975. Precision and recovery studies were evaluated at three concentration levels for Japonica, Indica, and Glutinous rice matrix. The mean recoveries obtained for all analytes in spiked Xiushui 03, Liangyoupeijiu, and Taihunuo rice samples were 83.3–99.0%, 82.0–99.7%, and 84.2–99.4%, respectively, with relative standard deviation in range 1.7–10.6%, 1.2–10.7%, and 1.9–11.6% for spiked rice samples, respectively. The intra-day precision (n = 5) for the 10 herbicides in rice samples spiked at an intermediate level was between 2.8% and 7.9%, and the inter-day precision over 10 days (n = 10) was between 5.5% and 15.9%.
Keywords: Triazine herbicides; Solid phase extraction; High resolution; High mass accuracy;
Matrix-assisted laser desorption/ionization-mass spectrometry of cuticular lipid profiles can differentiate sex, age, and mating status of Anopheles gambiae mosquitoes by Estrella Suarez; Hien P. Nguyen; Israel P. Ortiz; Kyu Jong Lee; Seoung Bum Kim; Jaroslaw Krzywinski; Kevin A. Schug (157-163).
Display Omitted► MALDI-MS can differentiate age, sex, and mating status of Anopheles gambiae mosquitoes. ► Silver is used as a cationization agent to observe cuticular hydrocarbon profiles. ► The method is 100% effective in age grading female A. gambiae.Malaria is a devastating mosquito-borne disease, which affects hundreds of millions of people each year. It is transmitted predominantly by Anopheles gambiae, whose females must be >10 days old to become infective. In this study, cuticular lipids from a laboratory strain of this mosquito species were analyzed using a mass spectrometry method to evaluate their utility for age, sex and mating status differentiation. Matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS), in conjunction with an acenaphthene/silver nitrate matrix preparation, was shown to be 100% effective in classifying A. gambiae females into 1, 7–10, and 14 days of age. MALDI-MS analysis, supported by multivariate statistical methods, was also effective in detecting cuticular lipid differences between the sexes and between virgin and mated females. The technique requires further testing, but the obtained results suggest that MALDI-MS cuticular lipid spectra could be used for age grading of A. gambiae females with precision greater than with other available methods.
Keywords: Malaria; Matrix-assisted laser desorption/ionization; Anopheles gambiae; Mosquito; Cuticular hydrocarbons; Cuticular lipids; Principal component analysis; Support vector machines;
1064 nm dispersive multichannel Raman spectroscopy for the analysis of plant lignin by Matthew W. Meyer; Jason S. Lupoi; Emily A. Smith (164-170).
Display Omitted► A 1064 nm dispersive multichannel Raman spectrometer is described. ► Raman spectra are collected for the heterogeneous phenylpropanoid biopolymer lignin. ► A quantitative analysis of lignin monomer composition is measured from Raman spectra.The mixed phenylpropanoid polymer lignin is one of the most abundant biopolymers on the planet and is used in the paper, pulp and biorenewable industries. For many downstream applications, the lignin monomeric composition is required, but traditional methods for performing this analysis do not necessarily represent the lignin composition as it existed in the plant. Herein, it is shown that Raman spectroscopy can be used to measure the lignin monomer composition. The use of 1064 nm excitation is needed for lignin analyses since high fluorescence backgrounds are measured at wavelengths as long as 785 nm. The instrument used for these measurements is a 1064 nm dispersive multichannel Raman spectrometer that is suitable for applications outside of the laboratory, for example in-field or in-line analyses and using remote sensing fiber optics. This spectrometer has the capability of acquiring toluene/acetonitrile spectra with 800 cm−1 spectral coverage, 6.5 cm−1 spectral resolution and 54 S/N ratio in 10 s using 280 mW incident laser powers. The 1135–1350 cm−1 and 1560–1650 cm−1 regions of the lignin spectrum can be used to distinguish among the three primary model lignin monomers: coumaric, ferulic and sinapic acids. Mixtures of the three model monomers and first derivative spectra or partial least squares analysis of the phenyl ring breathing modes around 1600 cm−1 are used to determine sugarcane lignin monomer composition. Lignin extracted from sugarcane is shown to have a predominant dimethoxylated and monomethoxylated phenylpropanoid content with a lesser amount of non-methoxylated phenol, which is consistent with sugarcane's classification as a non-woody angiosperm. The location of the phenyl ring breathing mode peaks do not shift in ethanol, methanol, isopropanol, 1,4 dioxane or acetone.
Keywords: 1064 nm dispersive multichannel Raman spectrometer; Lignin monomer composition; p-Hydroxyphenyl; Guaiacyl; Syringyl; Partial least squares;
Carbon nanotube–DNA hybrid used for activity monitoring and inhibitor screening of nuclease by Zhong De Liu; Ping Ping Hu; Heng Xin Zhao; Yuan Fang Li; Cheng Zhi Huang (171-175).
A versatile platform for monitoring the activity of nuclease and screening of its inhibitor with a fluorescence off–on–off strategy.Display Omitted► A self-assembled energy transfer-based quenching system was constructed. ► It can be utilized for activity monitoring and inhibitor screening of nuclease. ► The strategy has the advantages of high sensitivity and commonality.Carbon nanotubes (CNTs) can efficiently quench the fluorescence of the adsorbed fluorophores and nonconvalently interact with soft single-stranded DNA (ssDNA). Upon disruption of CNTs–fluorescent oligonucleotides hybrid by nuclease S1, fluorescence turn-on was observed. Using this strategy, a platform based on fluorescence signal for monitoring the activity of nuclease with advantages of high sensitivity and commonality was established, and a linear relationship between initial cleavage reaction rate and nuclease S1 concentration is found in the range of 0.6–8.0 U mL−1 with a detection limit of 0.08 U mL−1. Furthermore, by taking pyrophosphate as an example, we use the assay to evaluate the prohibition effect on nuclease, and the extent of fluorescence recovery decreased linearly with increasing the concentration of pyrophosphate in the range of 0.2–1.4 mM, implying that the cleavage reaction by nuclease S1 was prohibited, and therefore this fluorescence assay can also be conveniently utilized for inhibitor screening of nuclease.
Keywords: Carbon nanotubes–DNA hybrid; DNA cleavage; Fluorescence nuclease assay; Inhibitor screening;
Pressure-assisted electrokinetic injection for on-line enrichment in capillary electrophoresis–mass spectrometry: A sensitive method for measurement of ten haloacetic acids in drinking water by Huijuan Zhang; Jiping Zhu; Rocio Aranda-Rodriguez; Yong-Lai Feng (176-183).
Display Omitted► A simple and sensitive method was developed for determination of ten HAAs in drinking water. ► Pressure-assisted electrokinetic injection was used for sample introduction in CE–MS/MS. ► HAAs were enriched up to 20,000-fold into capillary without compromising separation. ► A simple clean-up method has been developed to eliminate the matrix effect on PAEKI.Haloacetic acids (HAAs) are by-products of the chlorination of drinking water containing natural organic matter and bromide. A simple and sensitive method has been developed for determination of ten HAAs in drinking water. The pressure-assisted electrokinetic injection (PAEKI), an on-line enrichment technique, was employed to introduce the sample into a capillary electrophoresis (CE)–electrospray ionization–tandem mass spectrometry system (ESI-MS/MS). HAAs were monitored in selected reaction monitoring mode. With 3 min of PAEKI time, the ten major HAAs (HAA10) in drinking water were enriched up to 20,000-fold into the capillary without compromising resolution. A simple solid phase clean-up method has been developed to eliminate the influence of ionic matrices from drinking water on PAEKI. Under conditions optimized for mass spectrometry, PAEKI and capillary electrophoresis, detection limits defined as three times ratio of signal to noise have been achieved in a range of 0.013–0.12 μg L−1 for ten HAAs in water sample. The overall recoveries for all ten HAAs in drinking water samples were between 76 and 125%. Six HAAs including monochloro- (MCAA), dichloro- (DCAA), trichloro- (TCAA), monobromo- (MBAA), bromochloro- (BCAA), and bromodichloroacetic acids (BDCAA) were found in tap water samples collected.
Keywords: Pressure-assisted electrokinetic injection; Haloacetic acids; Capillary electrophoresis–mass spectrometry; Solid phase clean-up; Drinking water;
The development of an evaluation method for capture columns used in two-dimensional liquid chromatography by Liwei Cao; Danhua Yu; Xinliang Wang; Yanxiong Ke; Yu Jin; Xinmiao Liang (184-190).
► The capture ability of a capture column was evaluated by introducing the parameter Δt R. ► It could be further promoted by adjusting the mobile phase of the first dimensional column and using complex sample analysis software system (CSASS). ► Finally, an RP/HILIC 2D-LC system with a C18 capture column was developed to demonstrate the practical application of this method.Capture columns are important interface tools for on line two-dimensional liquid chromatography (2D-LC). In this study, a systematic method was developed to evaluate and optimize the capture ability of capture columns by off-line method. First, the parameter Δt R (Δt R = t 2−t 1−t 0−W) was introduced to quantitatively represent the capture ability of the capture column by connecting a capture column behind the first dimensional column. Based on the value of Δt R, an appropriate capture column was selected after the first dimensional column was fixed. Then, the capture ability of the selected column was promoted by adjusting the mobile phase of the first dimensional column. Capture ability was also optimized using complex sample analysis software system (CSASS) software. Second, the elution mode of the trapped compounds on the capture column was investigated by connecting the capture column before the second dimensional column. More specifically, in mode I, capture column was connected to the second dimension without changing the flow rate direction and the trapped compounds must pass through the capture column and be eluted into the second dimensional column. The contrary connection mode was mode II. It was found that mode I is more suitable method for 2D-LC. Finally, an off-line reversed-phase/hydrophilic interaction liquid chromatography two-dimensional liquid chromatography (RP/HILIC 2D-LC) system with a C18 capture column was developed to demonstrate the practical application of this method.
Keywords: Capture column; Evaluation method; Two-dimensional liquid chromatography; Separation materials;
Separation and determination of arsenic species in water by selective exchange and hybrid resins by Nureddin Ben Issa; Vladana N. Rajaković-Ognjanović; Aleksandar D. Marinković; Ljubinka V. Rajaković (191-198).
Display Omitted► A simple and efficient method for separation and determination of arsenic species. ► A new hybrid resin HY-AgCl is effective for iAs and oAs analytical separation. ► SBAE resin was convenient for the separation of As(III) from As(V) and oAs species. ► HY-Fe resin was convenient for the separation of DMAs(V).A simple and efficient method for separation and determination of inorganic arsenic (iAs) and organic arsenic (oAs) in drinking, natural and wastewater was developed. If arsenic is present in water prevailing forms are inorganic acids of As(III) and As(V). oAs can be found in traces as monomethylarsenic acid, MMA(V), and dimethylarsenic acid, DMAs(V). Three types of resins: a strong base anion exchange (SBAE) and two hybrid (HY) resins: HY-Fe and HY-AgCl, based on the activity of hydrated iron oxides and a silver chloride were investigated. It was found that the sorption processes (ion exchange, adsorption and chemisorptions) of arsenic species on SBAE (ion exchange) and HY resins depend on pH values of water. The quantitative separation of molecular and ionic forms of iAs and oAs was achieved by SBAE and pH adjustment, the molecular form of As(III) that exists in the water at pH <8.0 was not bonded with SBAE, which was convenient for direct determination of As(III) concentration in the effluent. HY-Fe resin retained all arsenic species except DMAs(V), which makes possible direct measurements of this specie in the effluent. HY-AgCl resin retained all iAs which was convenient for direct determination of oAs species concentration in the effluent. The selective bonding of arsenic species on three types of resins makes possible the development of the procedure for measuring and calculation of all arsenic species in water. In order to determine capacity of resins the preliminary investigations were performed in batch system and fixed bed flow system. Resin capacities were calculated according to breakthrough points in a fixed bed flow system which is the first step in designing of solid phase extraction (SPE) module for arsenic speciation separation and determination. Arsenic adsorption behavior in the presence of impurities showed tolerance with the respect to potential interference of anionic compounds commonly found in natural water. Proposed method was established performing standard procedures: with external standard, certified reference material and standard addition method. Two analytical techniques: the inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectroscopy-hydride generation (AAS-GH) were comparatively applied for the determination of arsenic in all arsenic species in water. ICP-MS detection limit was 0.2 μg L−1 and relative standard deviation (RSD) of all arsenic species investigated was between 3.5 and 5.1%.
Keywords: Arsenic species; Hybrid resin; Ion-exchange resin; Silver chloride; Separation; ICP-MS;