Selected
papers from the latest issue:
Analytical chemistry of the persistent organic pollutants identified in the Stockholm Convention: A review
25 July 2013,
08:50:21
Publication date: 6 August
2013
Source:Analytica Chimica Acta, Volume 790
Author(s): Weiguang Xu , Xian Wang , Zongwei Cai
Persistent organic pollutants (POPs) are major environmental concern due to their persistence, long-range transportability, bio-accumulation and potentially adverse effects on living organisms. Analytical chemistry plays an essential role in the measurement of POPs and provides important information on their distribution and environmental transformations. Much effort has been devoted during the last two decades to the development of faster, safer, more reliable and more sensitive analytical techniques for these pollutants. Since the Stockholm Convention (SC) on POPs was adopted 12 years ago, analytical methods have been extensively developed. This review article introduces recent analytical techniques and applications for the determination of POPs in environmental and biota samples, and summarizes the extraction, separation and instrumental analyses of the halogenated POPs. Also, this review covers important aspects for the analyses of SC POPs (e.g. lipid determination and quality assurance/quality control (QA/QC)), and finally discusses future trends for improving the POPs analyses and for potential new POPs.
Source:Analytica Chimica Acta, Volume 790
Author(s): Weiguang Xu , Xian Wang , Zongwei Cai
Persistent organic pollutants (POPs) are major environmental concern due to their persistence, long-range transportability, bio-accumulation and potentially adverse effects on living organisms. Analytical chemistry plays an essential role in the measurement of POPs and provides important information on their distribution and environmental transformations. Much effort has been devoted during the last two decades to the development of faster, safer, more reliable and more sensitive analytical techniques for these pollutants. Since the Stockholm Convention (SC) on POPs was adopted 12 years ago, analytical methods have been extensively developed. This review article introduces recent analytical techniques and applications for the determination of POPs in environmental and biota samples, and summarizes the extraction, separation and instrumental analyses of the halogenated POPs. Also, this review covers important aspects for the analyses of SC POPs (e.g. lipid determination and quality assurance/quality control (QA/QC)), and finally discusses future trends for improving the POPs analyses and for potential new POPs.
Graphical abstract
Simultaneous measurement of two enzyme activities using infrared spectroscopy: A comparative evaluation of PARAFAC, TUCKER and N-PLS modeling
25 July 2013,
08:50:21
Publication date: 6 August
2013
Source:Analytica Chimica Acta, Volume 790
Author(s): Andreas Baum , Per Waaben Hansen , Anne S. Meyer , Jørn Dalgaard Mikkelsen
Enzymes are used in many processes to release fermentable sugars for green production of biofuel, or the refinery of biomass for extraction of functional food ingredients such as pectin or prebiotic oligosaccharides. The complex biomasses may, however, require a multitude of specific enzymes which are active on specific substrates generating a multitude of products. In this paper we use the plant polymer, pectin, to present a method to quantify enzyme activity of two pectolytic enzymes by monitoring their superimposed spectral evolutions simultaneously. The data is analyzed by three chemometric multiway methods, namely PARAFAC, TUCKER3 and N-PLS, to establish simultaneous enzyme activity assays for pectin lyase and pectin methyl esterase. Correlation coefficients R pred 2 for prediction test sets are 0.48, 0.96 and 0.96 for pectin lyase and 0.70, 0.89 and 0.89 for pectin methyl esterase, respectively. The retrieved models are compared and prediction test sets show that especially TUCKER3 performs well, even in comparison to the supervised regression method N-PLS.
Source:Analytica Chimica Acta, Volume 790
Author(s): Andreas Baum , Per Waaben Hansen , Anne S. Meyer , Jørn Dalgaard Mikkelsen
Enzymes are used in many processes to release fermentable sugars for green production of biofuel, or the refinery of biomass for extraction of functional food ingredients such as pectin or prebiotic oligosaccharides. The complex biomasses may, however, require a multitude of specific enzymes which are active on specific substrates generating a multitude of products. In this paper we use the plant polymer, pectin, to present a method to quantify enzyme activity of two pectolytic enzymes by monitoring their superimposed spectral evolutions simultaneously. The data is analyzed by three chemometric multiway methods, namely PARAFAC, TUCKER3 and N-PLS, to establish simultaneous enzyme activity assays for pectin lyase and pectin methyl esterase. Correlation coefficients R pred 2 for prediction test sets are 0.48, 0.96 and 0.96 for pectin lyase and 0.70, 0.89 and 0.89 for pectin methyl esterase, respectively. The retrieved models are compared and prediction test sets show that especially TUCKER3 performs well, even in comparison to the supervised regression method N-PLS.
Graphical abstract
Electrochemical immunoassay for thyroxine detection using cascade catalysis as signal amplified enhancer and multi-functionalized magnetic graphene sphere as signal tag
25 July 2013,
08:50:21
Publication date: 6 August
2013
Source:Analytica Chimica Acta, Volume 790
Author(s): Jing Han , Ying Zhuo , Yaqin Chai , Yanqing Yu , Ni Liao , Ruo Yuan
This paper constructed a reusable electrochemical immunosensor for the detection of thyroxine at an ultralow concentration using cascade catalysis of cytochrome c (Cyt c) and glucose oxidase (GOx) as signal amplified enhancer. It is worth pointing out that numerous Cyt c and GOx were firstly carried onto the double-stranded DNA polymers based on hybridization chain reaction (HCR), and then the amplified responses could be achieved by cascade catalysis of Cyt c and GOx recycling with the help of glucose. Moreover, multi-functionalized magnetic graphene sphere was synthesized and used as signal tag, which not only exhibited good mechanical properties, large surface area and an excellent electron transfer rate of graphene, but also possessed excellent redox activity and desirable magnetic property. With a sandwich-type immunoreaction, the proposed cascade catalysis amplification strategy could greatly enhance the sensitivity for the detection of thyroxine. Under the optimal conditions, the immunosensor showed a wide linear ranged from 0.05pgmL−1 to 5ngmL−1 and a low detection limit down to 15fgmL−1. Importantly, the proposed method offers promise for reproducible and cost-effective analysis of biological samples.
Source:Analytica Chimica Acta, Volume 790
Author(s): Jing Han , Ying Zhuo , Yaqin Chai , Yanqing Yu , Ni Liao , Ruo Yuan
This paper constructed a reusable electrochemical immunosensor for the detection of thyroxine at an ultralow concentration using cascade catalysis of cytochrome c (Cyt c) and glucose oxidase (GOx) as signal amplified enhancer. It is worth pointing out that numerous Cyt c and GOx were firstly carried onto the double-stranded DNA polymers based on hybridization chain reaction (HCR), and then the amplified responses could be achieved by cascade catalysis of Cyt c and GOx recycling with the help of glucose. Moreover, multi-functionalized magnetic graphene sphere was synthesized and used as signal tag, which not only exhibited good mechanical properties, large surface area and an excellent electron transfer rate of graphene, but also possessed excellent redox activity and desirable magnetic property. With a sandwich-type immunoreaction, the proposed cascade catalysis amplification strategy could greatly enhance the sensitivity for the detection of thyroxine. Under the optimal conditions, the immunosensor showed a wide linear ranged from 0.05pgmL−1 to 5ngmL−1 and a low detection limit down to 15fgmL−1. Importantly, the proposed method offers promise for reproducible and cost-effective analysis of biological samples.
Graphical abstract
Non-conductive nanomaterial enhanced electrochemical response in stripping voltammetry: The use of nanostructured magnesium silicate hollow spheres for heavy metal ions detection
25 July 2013,
08:50:21
Publication date: 6 August
2013
Source:Analytica Chimica Acta, Volume 790
Author(s): Ren-Xia Xu , Xin-Yao Yu , Chao Gao , Yu-Jing Jiang , Dong-Dong Han , Jin-Huai Liu , Xing-Jiu Huang
Nanostructured magnesium silicate hollow spheres, one kind of non-conductive nanomaterials, were used in heavy metal ions (HMIs) detection with enhanced performance for the first time. The detailed study of the enhancing electrochemical response in stripping voltammetry for simultaneous detection of ultratrace Cd2+, Pb2+, Cu2+ and Hg2+ was described. Electrochemical properties of modified electrodes were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The operational parameters which have influence on the deposition and stripping of metal ions, such as supporting electrolytes, pH value, and deposition time were carefully studied. The anodic stripping voltammetric performance toward HMIs was evaluated using square wave anodic stripping voltammetry (SWASV) analysis. The detection limits achieved (0.186nM, 0.247nM, 0.169nM and 0.375nM for Cd2+, Pb2+, Cu2+ and Hg2+) are much lower than the guideline values in drinking water given by the World Health Organization (WHO). In addition, the interference and stability of the modified electrode were also investigated under the optimized conditions. An interesting phenomenon of mutual interference between different metal ions was observed. Most importantly, the sensitivity of Pb2+ increased in the presence of certain concentrations of other metal ions, such as Cd2+, Cu2+ and Hg2+ both individually and simultaneously. The proposed electrochemical sensing method is thus expected to open new opportunities to broaden the use of SWASV in analysis for detecting HMIs in the environment.
Source:Analytica Chimica Acta, Volume 790
Author(s): Ren-Xia Xu , Xin-Yao Yu , Chao Gao , Yu-Jing Jiang , Dong-Dong Han , Jin-Huai Liu , Xing-Jiu Huang
Nanostructured magnesium silicate hollow spheres, one kind of non-conductive nanomaterials, were used in heavy metal ions (HMIs) detection with enhanced performance for the first time. The detailed study of the enhancing electrochemical response in stripping voltammetry for simultaneous detection of ultratrace Cd2+, Pb2+, Cu2+ and Hg2+ was described. Electrochemical properties of modified electrodes were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The operational parameters which have influence on the deposition and stripping of metal ions, such as supporting electrolytes, pH value, and deposition time were carefully studied. The anodic stripping voltammetric performance toward HMIs was evaluated using square wave anodic stripping voltammetry (SWASV) analysis. The detection limits achieved (0.186nM, 0.247nM, 0.169nM and 0.375nM for Cd2+, Pb2+, Cu2+ and Hg2+) are much lower than the guideline values in drinking water given by the World Health Organization (WHO). In addition, the interference and stability of the modified electrode were also investigated under the optimized conditions. An interesting phenomenon of mutual interference between different metal ions was observed. Most importantly, the sensitivity of Pb2+ increased in the presence of certain concentrations of other metal ions, such as Cd2+, Cu2+ and Hg2+ both individually and simultaneously. The proposed electrochemical sensing method is thus expected to open new opportunities to broaden the use of SWASV in analysis for detecting HMIs in the environment.
Graphical abstract
Determination of hormones in milk by hollow fiber-based stirring extraction bar liquid–liquid microextraction gas chromatography mass spectrometry
25 July 2013,
08:50:21
Publication date: 6 August
2013
Source:Analytica Chimica Acta, Volume 790
Author(s): Xu Xu , Fanghui Liang , Jiayuan Shi , Xin Zhao , Zhuang Liu , Lijie Wu , Ying Song , Hanqi Zhang , Ziming Wang
The hollow fiber-based stirring extraction bar liquid–liquid microextraction was applied to the extraction of hormones, including 17-α-ethinylestradiol, 17-α-estradiol, estriol, 17-β-estradiol, estrone, 17-α-hydroxyprogesterone, medroxyprogesterone, progesterone and norethisterone acetate, in milk. The present method has the advantages of both hollow fiber-liquid phase microextraction and stirring bar sorptive extraction. The stirring extraction bar was used as both the stirring bar of microextraction, and extractor of the analytes, which can make extraction, clean-up and concentration be carried out in one step. When the extraction was completed, the stirring extraction bar was easy isolated from the extraction system with the magnet. Several experimental parameters, including the type of extraction solvent, the number of hollow stirring extraction bar, extraction time, stirring speed, ionic strength, and desorption conditions were investigated and optimized. The analytes in the extract were derived and determined by gas chromatography mass spectrometry. Under optimal experimental conditions, good linearity was observed in the range of 0.20–20.00ngmL−1. The limits of detection and quantification were in the range of 0.02–0.06ngmL−1 and 0.07–0.19ngmL−1, respectively. The present method was applied to the analysis of milk samples, and the recoveries of analytes were in the range of 93.6–104.6% with the relative standard deviations ranging from 1.6% to 6.2% (n =5). The results showed that the present method was a rapid and feasible method for the determination of hormones in milk samples.
Source:Analytica Chimica Acta, Volume 790
Author(s): Xu Xu , Fanghui Liang , Jiayuan Shi , Xin Zhao , Zhuang Liu , Lijie Wu , Ying Song , Hanqi Zhang , Ziming Wang
The hollow fiber-based stirring extraction bar liquid–liquid microextraction was applied to the extraction of hormones, including 17-α-ethinylestradiol, 17-α-estradiol, estriol, 17-β-estradiol, estrone, 17-α-hydroxyprogesterone, medroxyprogesterone, progesterone and norethisterone acetate, in milk. The present method has the advantages of both hollow fiber-liquid phase microextraction and stirring bar sorptive extraction. The stirring extraction bar was used as both the stirring bar of microextraction, and extractor of the analytes, which can make extraction, clean-up and concentration be carried out in one step. When the extraction was completed, the stirring extraction bar was easy isolated from the extraction system with the magnet. Several experimental parameters, including the type of extraction solvent, the number of hollow stirring extraction bar, extraction time, stirring speed, ionic strength, and desorption conditions were investigated and optimized. The analytes in the extract were derived and determined by gas chromatography mass spectrometry. Under optimal experimental conditions, good linearity was observed in the range of 0.20–20.00ngmL−1. The limits of detection and quantification were in the range of 0.02–0.06ngmL−1 and 0.07–0.19ngmL−1, respectively. The present method was applied to the analysis of milk samples, and the recoveries of analytes were in the range of 93.6–104.6% with the relative standard deviations ranging from 1.6% to 6.2% (n =5). The results showed that the present method was a rapid and feasible method for the determination of hormones in milk samples.
Graphical abstract
Combination of computational methods, adsorption isotherms and selectivity tests for the conception of a mixed non-covalent–semi-covalent molecularly imprinted polymer of vanillin
25 July 2013,
08:50:21
Publication date: 6 August
2013
Source:Analytica Chimica Acta, Volume 790
Author(s): Kinga Puzio , Raphaël Delépée , Richard Vidal , Luigi A. Agrofoglio
A novel molecularly imprinted polymer (MIP) for vanillin was prepared by photo initiated polymerization in dichloromethane using a mixed semi-covalent and non-covalent imprinting strategy. Taking polymerisable syringaldehyde as “dummy” template, acrylamide was chosen as functional monomer on B3LYP/6-31+G(d,p) density functional theory computational method basis with counterpoise. The binding parameters for the recognition of vanillin on imprinted polymers were studied with three different isotherm models (Langmuir, bi-Langmuir and Langmuir–Freundlich) and compared. The results indicate an heterogeneity of binding sites. It was found and proved by DFT calculations that the specific binding of vanillin in the cavities is due to non-covalent interactions of the template with the hydroxyphenyl- and the amide-moieties. The binding geometry of vanillin in the MIP cavity was also modelled. The obtained MIP is highly specific for vanillin (with an imprinting factor of 7.4) and was successfully applied to the extraction of vanillin from vanilla pods, red wine spike with vanillin, natural and artificial vanilla sugar with a recovery of 80%.
Source:Analytica Chimica Acta, Volume 790
Author(s): Kinga Puzio , Raphaël Delépée , Richard Vidal , Luigi A. Agrofoglio
A novel molecularly imprinted polymer (MIP) for vanillin was prepared by photo initiated polymerization in dichloromethane using a mixed semi-covalent and non-covalent imprinting strategy. Taking polymerisable syringaldehyde as “dummy” template, acrylamide was chosen as functional monomer on B3LYP/6-31+G(d,p) density functional theory computational method basis with counterpoise. The binding parameters for the recognition of vanillin on imprinted polymers were studied with three different isotherm models (Langmuir, bi-Langmuir and Langmuir–Freundlich) and compared. The results indicate an heterogeneity of binding sites. It was found and proved by DFT calculations that the specific binding of vanillin in the cavities is due to non-covalent interactions of the template with the hydroxyphenyl- and the amide-moieties. The binding geometry of vanillin in the MIP cavity was also modelled. The obtained MIP is highly specific for vanillin (with an imprinting factor of 7.4) and was successfully applied to the extraction of vanillin from vanilla pods, red wine spike with vanillin, natural and artificial vanilla sugar with a recovery of 80%.
Graphical abstract
Use of a mobile phone for potentiostatic control with low cost paper-based microfluidic sensors
25 July 2013,
08:50:21
Publication date: 6 August
2013
Source:Analytica Chimica Acta, Volume 790
Author(s): Jacqui L. Delaney , Egan H. Doeven , Anthony J. Harsant , Conor F. Hogan
By exploiting its ability to play sounds, a mobile phone with suitable software installed can serve the basic functions of a potentiostat in controlling an applied potential to oxidise ECL-active molecules, while the resultant photonic signal is monitored using the camera in video mode. In combination with paper microfluidic sensors this opens significant new possibilities for low-cost, instrument-free sensing.
Source:Analytica Chimica Acta, Volume 790
Author(s): Jacqui L. Delaney , Egan H. Doeven , Anthony J. Harsant , Conor F. Hogan
By exploiting its ability to play sounds, a mobile phone with suitable software installed can serve the basic functions of a potentiostat in controlling an applied potential to oxidise ECL-active molecules, while the resultant photonic signal is monitored using the camera in video mode. In combination with paper microfluidic sensors this opens significant new possibilities for low-cost, instrument-free sensing.
Graphical abstract
A reliable and environmentally-friendly liquid-chromatographic method for multi-class determination of fat-soluble UV filters in cosmetic products
25 July 2013,
08:50:21
Publication date: 6 August
2013
Source:Analytica Chimica Acta, Volume 790
Author(s): Alberto Chisvert , Isuha Tarazona , Amparo Salvador
An environmentally-friendly analytical method for the simultaneous determination of 15 fat-soluble ultraviolet (UV) filters currently authorized by the European Union regulation on cosmetic products has been developed. The determination was performed by liquid chromatography with UV spectrophotometric detection. Different parameters, such as type of column, oven temperature, mobile phase composition and flow rate were studied. The best chromatographic separation was obtained under the following conditions: C18 column set at 60°C and gradient ethanol:water (containing 1% formic acid and 20mM of 2-hydroxypropyl-β-cyclodextrin) as mobile phase pumped at 1mLmin−1. 2-Hydroxypropyl-β-cyclodextrin was added as mobile phase modifier to achieve the complete resolution of some of the chromatographic peaks. The 15 target compounds were separated in less than 30min. The method was satisfactorily validated by analyzing three laboratory-made cosmetic samples besides of eleven commercially available cosmetic products containing different combination of the target UV filters. Good accordance of the found levels compared with those of the laboratory-made samples and those of the commercial samples (when available) was achieved. Moreover, excellent recoveries (97–104%) and good intra-day and inter-day precision values at different concentration levels, besides limits of detection values below the μgmL−1 level, were obtained. These good analytical features, as well as their environmentally-friendly characteristics, make the presented method suitable not only for routine analysis in cosmetics industries, but also as candidate reference method for sunscreen analysis.
Source:Analytica Chimica Acta, Volume 790
Author(s): Alberto Chisvert , Isuha Tarazona , Amparo Salvador
An environmentally-friendly analytical method for the simultaneous determination of 15 fat-soluble ultraviolet (UV) filters currently authorized by the European Union regulation on cosmetic products has been developed. The determination was performed by liquid chromatography with UV spectrophotometric detection. Different parameters, such as type of column, oven temperature, mobile phase composition and flow rate were studied. The best chromatographic separation was obtained under the following conditions: C18 column set at 60°C and gradient ethanol:water (containing 1% formic acid and 20mM of 2-hydroxypropyl-β-cyclodextrin) as mobile phase pumped at 1mLmin−1. 2-Hydroxypropyl-β-cyclodextrin was added as mobile phase modifier to achieve the complete resolution of some of the chromatographic peaks. The 15 target compounds were separated in less than 30min. The method was satisfactorily validated by analyzing three laboratory-made cosmetic samples besides of eleven commercially available cosmetic products containing different combination of the target UV filters. Good accordance of the found levels compared with those of the laboratory-made samples and those of the commercial samples (when available) was achieved. Moreover, excellent recoveries (97–104%) and good intra-day and inter-day precision values at different concentration levels, besides limits of detection values below the μgmL−1 level, were obtained. These good analytical features, as well as their environmentally-friendly characteristics, make the presented method suitable not only for routine analysis in cosmetics industries, but also as candidate reference method for sunscreen analysis.
Graphical abstract
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