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Analytica Chimica Acta (v.757, #)
Novel sorption-based methodologies for static microextraction analysis: A review on SBSE and related techniques by J.M.F. Nogueira (pp. 1-10).
Display Omitted► State-of-the-art in SBSE. ► Main limitations of SBSE. ► Adsorptive microextraction (AμE) techniques.Stir bar sorptive extraction (SBSE) became a well-established analytical technique in the last years, for which hundreds of applications in almost all types of scientific fields can be found in the literature. In spite of the great enrichment capacity and outstanding performance to operate at the ultra-trace level, this remarkable static sorption-based method is already not quite effective for some complex systems, in particular to monitor the large group of polar organic compounds. This review aims to cover the state-of-the-art in SBSE, as well as supplying a discussion of the analytical potential of the novel adsorptive microextraction techniques, as complementary enrichment approaches, by explaining the main principles and providing technical know-how for the beginners.
Keywords: Trace analysis; Static microextraction; Sample enrichment; Sorption-based methods; Floating sampling techniques; SBSE; AμE; BAμE; MSAμE; PDMS; Sorbent phases; Nanoparticles; Activated carbons; Polymeric coatings
Novel sorption-based methodologies for static microextraction analysis: A review on SBSE and related techniques by J.M.F. Nogueira (pp. 1-10).
Display Omitted► State-of-the-art in SBSE. ► Main limitations of SBSE. ► Adsorptive microextraction (AμE) techniques.Stir bar sorptive extraction (SBSE) became a well-established analytical technique in the last years, for which hundreds of applications in almost all types of scientific fields can be found in the literature. In spite of the great enrichment capacity and outstanding performance to operate at the ultra-trace level, this remarkable static sorption-based method is already not quite effective for some complex systems, in particular to monitor the large group of polar organic compounds. This review aims to cover the state-of-the-art in SBSE, as well as supplying a discussion of the analytical potential of the novel adsorptive microextraction techniques, as complementary enrichment approaches, by explaining the main principles and providing technical know-how for the beginners.
Keywords: Trace analysis; Static microextraction; Sample enrichment; Sorption-based methods; Floating sampling techniques; SBSE; AμE; BAμE; MSAμE; PDMS; Sorbent phases; Nanoparticles; Activated carbons; Polymeric coatings
Reproducibility, complementary measure of predictability for robustness improvement of multivariate calibration models via variable selections by Hae Woo Lee; Andrew Bawn; Seongkyu Yoon (pp. 11-18).
Display Omitted► New reproducibility measure is developed and addressed as robustness measure of models. ► 5 variable selection methods were investigated by Monte-Carlo sub-sampling (MCS). ► Investigation of reproducibility and prediction accuracy was done with two NIR datasets. ► Thorough assessment of variable selection could improve robustness of calibration models.In multivariate calibration with the spectral dataset, variable selection is often applied to identify relevant subset of variables, leading to improved prediction accuracy and easy interpretation of the selected fingerprint regions. Until now, numerous variable selection methods have been proposed, but a proper choice among them is not trivial. Furthermore, in many cases, a set of variables found by those methods might not be robust due to the irreproducibility and uncertainty issues, posing a great challenge in improving the reliability of the variable selection. In this study, the reproducibility of the 5 variable selection methods was investigated quantitatively for evaluating their performance. The reproducibility of variable selection was quantified by using Monte-Carlo sub-sampling (MCS) techniques together with the quantitative similarity measure designed for the highly collinear spectral dataset. The investigation of reproducibility and prediction accuracy of the several variable selection algorithms with two different near-infrared (NIR) datasets illustrated that the different variable selection methods exhibited wide variability in their performance, especially in their capabilities to identify the consistent subset of variables from the spectral datasets. Thus the thorough assessment of the reproducibility together with the predictive accuracy of the identified variables improved the statistical validity and confidence of the selection outcome, which cannot be addressed by the conventional evaluation schemes.
Keywords: Variable selection; Multivariate calibration; Reproducibility; Near-infrared (NIR); Partial least squares
Reproducibility, complementary measure of predictability for robustness improvement of multivariate calibration models via variable selections by Hae Woo Lee; Andrew Bawn; Seongkyu Yoon (pp. 11-18).
Display Omitted► New reproducibility measure is developed and addressed as robustness measure of models. ► 5 variable selection methods were investigated by Monte-Carlo sub-sampling (MCS). ► Investigation of reproducibility and prediction accuracy was done with two NIR datasets. ► Thorough assessment of variable selection could improve robustness of calibration models.In multivariate calibration with the spectral dataset, variable selection is often applied to identify relevant subset of variables, leading to improved prediction accuracy and easy interpretation of the selected fingerprint regions. Until now, numerous variable selection methods have been proposed, but a proper choice among them is not trivial. Furthermore, in many cases, a set of variables found by those methods might not be robust due to the irreproducibility and uncertainty issues, posing a great challenge in improving the reliability of the variable selection. In this study, the reproducibility of the 5 variable selection methods was investigated quantitatively for evaluating their performance. The reproducibility of variable selection was quantified by using Monte-Carlo sub-sampling (MCS) techniques together with the quantitative similarity measure designed for the highly collinear spectral dataset. The investigation of reproducibility and prediction accuracy of the several variable selection algorithms with two different near-infrared (NIR) datasets illustrated that the different variable selection methods exhibited wide variability in their performance, especially in their capabilities to identify the consistent subset of variables from the spectral datasets. Thus the thorough assessment of the reproducibility together with the predictive accuracy of the identified variables improved the statistical validity and confidence of the selection outcome, which cannot be addressed by the conventional evaluation schemes.
Keywords: Variable selection; Multivariate calibration; Reproducibility; Near-infrared (NIR); Partial least squares
Statistical methods for improving verification of claims of origin for Italian wines based on stable isotope ratios by N. Dordevic; R. Wehrens; G.J. Postma; L.M.C. Buydens; F. Camin (pp. 19-25).
Display Omitted► The assessment of claims of origin is of enormous economic importance for DOC and DOCG wines. ► The official method is based on univariate statistical tests of H, C and O isotopic ratios. ► We consider 5220 Italian wine samples collected in the period 2000–2010. ► Multivariate statistical analysis leads to much better specificity and easier detection of false claims of origin. ► In the case of multi-modal data, mixture modelling provides additional improvements.Wine derives its economic value to a large extent from geographical origin, which has a significant impact on the quality of the wine. According to the food legislation, wines can be without geographical origin (table wine) and wines with origin. Wines with origin must have characteristics which are essential due to its region of production and must be produced, processed and prepared, exclusively within that region.The development of fast and reliable analytical methods for the assessment of claims of origin is very important. The current official method is based on the measurement of stable isotope ratios of water and alcohol in wine, which are influenced by climatic factors. The results in this paper are based on 5220 Italian wine samples collected in the period 2000–2010. We evaluate the univariate approach underlying the official method to assess claims of origin and propose several new methods to get better geographical discrimination between samples. It is shown that multivariate methods are superior to univariate approaches in that they show increased sensitivity and specificity. In cases where data are non-normally distributed, an approach based on mixture modelling provides additional improvements.
Keywords: H, C and O isotopes; EU Wine Databank; Regional origin; Univariate; Multivariate; Mixture modelling
Statistical methods for improving verification of claims of origin for Italian wines based on stable isotope ratios by N. Dordevic; R. Wehrens; G.J. Postma; L.M.C. Buydens; F. Camin (pp. 19-25).
Display Omitted► The assessment of claims of origin is of enormous economic importance for DOC and DOCG wines. ► The official method is based on univariate statistical tests of H, C and O isotopic ratios. ► We consider 5220 Italian wine samples collected in the period 2000–2010. ► Multivariate statistical analysis leads to much better specificity and easier detection of false claims of origin. ► In the case of multi-modal data, mixture modelling provides additional improvements.Wine derives its economic value to a large extent from geographical origin, which has a significant impact on the quality of the wine. According to the food legislation, wines can be without geographical origin (table wine) and wines with origin. Wines with origin must have characteristics which are essential due to its region of production and must be produced, processed and prepared, exclusively within that region.The development of fast and reliable analytical methods for the assessment of claims of origin is very important. The current official method is based on the measurement of stable isotope ratios of water and alcohol in wine, which are influenced by climatic factors. The results in this paper are based on 5220 Italian wine samples collected in the period 2000–2010. We evaluate the univariate approach underlying the official method to assess claims of origin and propose several new methods to get better geographical discrimination between samples. It is shown that multivariate methods are superior to univariate approaches in that they show increased sensitivity and specificity. In cases where data are non-normally distributed, an approach based on mixture modelling provides additional improvements.
Keywords: H, C and O isotopes; EU Wine Databank; Regional origin; Univariate; Multivariate; Mixture modelling
Selenium metabolomics in yeast using complementary reversed-phase/hydrophilic ion interaction (HILIC) liquid chromatography–electrospray hybrid quadrupole trap/Orbitrap mass spectrometry by C. Arnaudguilhem; K. Bierla; L. Ouerdane; H. Preud’homme; A. Yiannikouris; R. Lobinski (pp. 26-38).
Display Omitted► The use of bimodal chromatographic separation enlarged amount of compounds identified. ► The method allowed the largest scale ever (>60 compounds) speciation analysis of selenium metabolites in Se-rich yeast. ► The estimated concentration of compounds was given.A high efficiency chromatographic separation on a porous graphitic carbon stationary phase was developed for a large-scale separation of selenium metabolites in Se-rich yeast prior to their identification by electrospray hybrid quadrupole trap/Orbitrap mass spectrometry (Orbitrap MS n). The reversed-phase (RP) separation mode offered distinctly higher separation efficiency than the hydrophilic ion interaction (HILIC) mode. The latter was nevertheless complementary and useful to validate the detection of several compounds. The method allowed the detection of 64 metabolites including 30 SeSe or SeS conjugates (3 triple S/Se/S ones) and 14 selenoethers. 21 previously unreported metabolites were detected on the basis of the selenium isotopic pattern usually matched with the sub-ppm mass accuracy. 9 of these metabolites were subsequently identified using the multi-stage high mass accuracy (<5ppm) mass spectrometry. The identified metabolites (and their groups) were quantified on-line by ICP-MS fitted with a frequency-matching generator allowing a quasi-uniform response over the large (20–90%) acetonitrile mobile phase concentration range. The morphology of HPLC–ICP-MS chromatograms was remarkably similar to that of HPLC multi-ion extracted ESI-MS chromatograms. The detection limits obtained by ICP MS and ESI MS were 1 and 2ppb, respectively.
Keywords: Selenium; Speciation; Orbitrap; ICP MS; Porous graphitic carbon
Selenium metabolomics in yeast using complementary reversed-phase/hydrophilic ion interaction (HILIC) liquid chromatography–electrospray hybrid quadrupole trap/Orbitrap mass spectrometry by C. Arnaudguilhem; K. Bierla; L. Ouerdane; H. Preud’homme; A. Yiannikouris; R. Lobinski (pp. 26-38).
Display Omitted► The use of bimodal chromatographic separation enlarged amount of compounds identified. ► The method allowed the largest scale ever (>60 compounds) speciation analysis of selenium metabolites in Se-rich yeast. ► The estimated concentration of compounds was given.A high efficiency chromatographic separation on a porous graphitic carbon stationary phase was developed for a large-scale separation of selenium metabolites in Se-rich yeast prior to their identification by electrospray hybrid quadrupole trap/Orbitrap mass spectrometry (Orbitrap MS n). The reversed-phase (RP) separation mode offered distinctly higher separation efficiency than the hydrophilic ion interaction (HILIC) mode. The latter was nevertheless complementary and useful to validate the detection of several compounds. The method allowed the detection of 64 metabolites including 30 SeSe or SeS conjugates (3 triple S/Se/S ones) and 14 selenoethers. 21 previously unreported metabolites were detected on the basis of the selenium isotopic pattern usually matched with the sub-ppm mass accuracy. 9 of these metabolites were subsequently identified using the multi-stage high mass accuracy (<5ppm) mass spectrometry. The identified metabolites (and their groups) were quantified on-line by ICP-MS fitted with a frequency-matching generator allowing a quasi-uniform response over the large (20–90%) acetonitrile mobile phase concentration range. The morphology of HPLC–ICP-MS chromatograms was remarkably similar to that of HPLC multi-ion extracted ESI-MS chromatograms. The detection limits obtained by ICP MS and ESI MS were 1 and 2ppb, respectively.
Keywords: Selenium; Speciation; Orbitrap; ICP MS; Porous graphitic carbon
Rapid simultaneous screening and identification of multiple pesticide residues in vegetables by Fang Zhang; Chongtian Yu; Wenwen Wang; Ruojing Fan; Zhixu Zhang; Yinlong Guo (pp. 39-47).
Display Omitted► The method was set up for a universal screening of pesticide residues. ► The database included retention time, a single characteristic ion and a pair of ions. ► GC–QTOF MS as a new instrument system was applied due to its improving sensitivity and accuracy. ► Limit of identification of the database was at 5ppb in this case and accurate mass errors less than 2.5mDa. ► Thirteen pesticides were found in the vegetables (11 in celery, 9 in rape, 3 in scallion and 2 in spinach).A method for the rapid simultaneous screening and identification of multiple pesticide residues in vegetables was established using a novel database and gas chromatography in combination with hybrid quadrupole time-of-flight mass spectrometry (GC–QTOF MS). A total of 187 pesticides with different chemical species were measured by GC–QTOF MS to create the database, which collected the retention time and exact masses of ions from the first-stage mass spectrum (MS1 spectrum) and second-stage mass spectrum (MS2 spectrum) for each pesticide. The workflow of the created database consisted of “MS1 screening” for possible pesticides by chemical formula match and “MS2 identification” for structural confirmation of product ion by accurate mass measurement. To evaluate the applicability of the database, a spinach matrix was prepared by solid phase extraction, spiked with a mixture of 50 pesticides at seven concentrations between 0.1 and 10ppb, and analyzed by GC–QTOF MS. It was found that all of the 50 pesticides with concentrations as low as 5ppb were detected in the “MS1 screening” step and accurate masses were identified with errors less than 2.5mDa in the “MS2 identification” step, indicating high sensitivity, accuracy, selectivity and specificity. Finally, to validate the applicability, the new method was applied to four fresh celery, rape, scallion and spinach vegetables from a local market. As a result, a total of 13 pesticides were found, with 11 in celery, 9 in rape, 3 in scallion and 2 in spinach. In conclusion, GC–QTOF MS combined with an exact mass database is one of the most efficient tools for the analysis of pesticide residues in vegetables.
Keywords: Pesticide residues; Database; Screening; Structural identification; Gas chromatography–quadrupole time-of-flight mass spectrometry (GC–QTOF MS)
Rapid simultaneous screening and identification of multiple pesticide residues in vegetables by Fang Zhang; Chongtian Yu; Wenwen Wang; Ruojing Fan; Zhixu Zhang; Yinlong Guo (pp. 39-47).
Display Omitted► The method was set up for a universal screening of pesticide residues. ► The database included retention time, a single characteristic ion and a pair of ions. ► GC–QTOF MS as a new instrument system was applied due to its improving sensitivity and accuracy. ► Limit of identification of the database was at 5ppb in this case and accurate mass errors less than 2.5mDa. ► Thirteen pesticides were found in the vegetables (11 in celery, 9 in rape, 3 in scallion and 2 in spinach).A method for the rapid simultaneous screening and identification of multiple pesticide residues in vegetables was established using a novel database and gas chromatography in combination with hybrid quadrupole time-of-flight mass spectrometry (GC–QTOF MS). A total of 187 pesticides with different chemical species were measured by GC–QTOF MS to create the database, which collected the retention time and exact masses of ions from the first-stage mass spectrum (MS1 spectrum) and second-stage mass spectrum (MS2 spectrum) for each pesticide. The workflow of the created database consisted of “MS1 screening” for possible pesticides by chemical formula match and “MS2 identification” for structural confirmation of product ion by accurate mass measurement. To evaluate the applicability of the database, a spinach matrix was prepared by solid phase extraction, spiked with a mixture of 50 pesticides at seven concentrations between 0.1 and 10ppb, and analyzed by GC–QTOF MS. It was found that all of the 50 pesticides with concentrations as low as 5ppb were detected in the “MS1 screening” step and accurate masses were identified with errors less than 2.5mDa in the “MS2 identification” step, indicating high sensitivity, accuracy, selectivity and specificity. Finally, to validate the applicability, the new method was applied to four fresh celery, rape, scallion and spinach vegetables from a local market. As a result, a total of 13 pesticides were found, with 11 in celery, 9 in rape, 3 in scallion and 2 in spinach. In conclusion, GC–QTOF MS combined with an exact mass database is one of the most efficient tools for the analysis of pesticide residues in vegetables.
Keywords: Pesticide residues; Database; Screening; Structural identification; Gas chromatography–quadrupole time-of-flight mass spectrometry (GC–QTOF MS)
Rapid identification of trimethyl and triethyl amines using sulphonic acidic ionic liquids: A time-of-flight secondary ion mass spectrometry study of fragmentation reactions by Bhaskar Garg; Shiou-Ling Lei; Shou-Ching Liu; Tanuja Bisht; Jen-Yu Liu; Yong-Chien Ling (pp. 48-55).
Display Omitted► The easy derivatization of tertiaryalkyl amines into TSILs. ► The use of TOF-SIMS and TSILs for unswerving determination of tertiaryalkyl amines. ► The fragmentation pathways of TSILs under UHV. ► The detection limit of up to 10ppm for tertiaryalkyl amines.The time-of-flight secondary ion mass spectrometry (TOF-SIMS) has emerged as a powerful tool for the unswerving detection of biomolecules, in particular, proteins and peptides. To date, there is very little information available on the direct determination of trimethyl/triethyl amines using TOF-SIMS. One major hurdle in this regard is an ultrahigh vacuum system, usually needed in TOF-SIMS, which hampers its usability to trimethyl/triethyl amines owing to their high evaporation rate. We designed an efficient and sensitive protocol for rapid identification and sensitive determination of tertiaryalkyl amines using TOF-SIMS. The amines were derivatized by reaction with 1,4-butane sultone and sulphuric acid sequentially to afford the corresponding sulphonic acidic ionic liquids (ILs). The TOF-SIMS analysis of these task-specific ILs (TSILs) was carried out in both positive and negative polarity. The positive ion mass spectra of TSILs showed sharp fragmented peaks for tertiaryalkyl amines at typical level and up to 10ppm. The possible mechanism for different fragmentation pathways in positive polarity was discussed.
Keywords: Abbreviations; TOF-SIMS; time-of-flight secondary ion mass spectrometry; UHV; ultrahigh vacuum; RTILs; room temperature ionic liquids; TSILs; task-specific ionic liquids; VOCs; volatile organic compounds; DDA; N,N-dimethyldodecylamine; [TMBSA][HSO; 4; ]; N-(4-sulphonic acid)butyl trimethylammonium hydrogen sulphate; [TMBSA][HSO; 4; ]; N-(4-sulphonic acid)butyl triethylammonium hydrogen sulphate; TMA; trimethyl amine; TEA; triethyl amine; BS; 1,4-butane sultoneSulphonic acidic ionic liquids; Tertiaryalkyl amine; Time-of-flight secondary ion mass spectrometry; Derivatization; Fragmentation
Rapid identification of trimethyl and triethyl amines using sulphonic acidic ionic liquids: A time-of-flight secondary ion mass spectrometry study of fragmentation reactions by Bhaskar Garg; Shiou-Ling Lei; Shou-Ching Liu; Tanuja Bisht; Jen-Yu Liu; Yong-Chien Ling (pp. 48-55).
Display Omitted► The easy derivatization of tertiaryalkyl amines into TSILs. ► The use of TOF-SIMS and TSILs for unswerving determination of tertiaryalkyl amines. ► The fragmentation pathways of TSILs under UHV. ► The detection limit of up to 10ppm for tertiaryalkyl amines.The time-of-flight secondary ion mass spectrometry (TOF-SIMS) has emerged as a powerful tool for the unswerving detection of biomolecules, in particular, proteins and peptides. To date, there is very little information available on the direct determination of trimethyl/triethyl amines using TOF-SIMS. One major hurdle in this regard is an ultrahigh vacuum system, usually needed in TOF-SIMS, which hampers its usability to trimethyl/triethyl amines owing to their high evaporation rate. We designed an efficient and sensitive protocol for rapid identification and sensitive determination of tertiaryalkyl amines using TOF-SIMS. The amines were derivatized by reaction with 1,4-butane sultone and sulphuric acid sequentially to afford the corresponding sulphonic acidic ionic liquids (ILs). The TOF-SIMS analysis of these task-specific ILs (TSILs) was carried out in both positive and negative polarity. The positive ion mass spectra of TSILs showed sharp fragmented peaks for tertiaryalkyl amines at typical level and up to 10ppm. The possible mechanism for different fragmentation pathways in positive polarity was discussed.
Keywords: Abbreviations; TOF-SIMS; time-of-flight secondary ion mass spectrometry; UHV; ultrahigh vacuum; RTILs; room temperature ionic liquids; TSILs; task-specific ionic liquids; VOCs; volatile organic compounds; DDA; N,N-dimethyldodecylamine; [TMBSA][HSO; 4; ]; N-(4-sulphonic acid)butyl trimethylammonium hydrogen sulphate; [TMBSA][HSO; 4; ]; N-(4-sulphonic acid)butyl triethylammonium hydrogen sulphate; TMA; trimethyl amine; TEA; triethyl amine; BS; 1,4-butane sultoneSulphonic acidic ionic liquids; Tertiaryalkyl amine; Time-of-flight secondary ion mass spectrometry; Derivatization; Fragmentation
Gold–platinum alloy nanowires as highly sensitive materials for electrochemical detection of hydrogen peroxide by Yibo Zhou; Gang Yu; Fangfang Chang; Bonian Hu; Chuan-Jian Zhong (pp. 56-62).
Display Omitted► An effective strategy is demonstrated for preparing alloy nanowires as sensing materials. ► The alloy nanowires exhibit electrocatalytic activity for the reduction of hydrogen peroxide. ► The alloy nanowires function as an excellent sensor for the detection of hydrogen peroxide. ► The sensor shows a high sensitivity, low detection limit, and fast response time.The exploitation of the unique electrical properties of nanowires requires an effective assembly of nanowires as functional materials on a signal transduction platform. This paper describes a new strategy to assemble gold–platinum alloy nanowires on microelectrode devices and demonstrates the sensing characteristics to hydrogen peroxide. The alloy nanowires have been controllably electrodeposited on microelectrodes by applying an alternating current. The composition, morphology and alloying structures of the nanowires were characterized, revealing a single-phase alloy characteristic, highly monodispersed morphology, and controllable bimetallic compositions. The alloy nanowires were shown to exhibit electrocatalytic response characteristics for the detection of hydrogen peroxide, exhibiting a high sensitivity, low detection limit, and fast response time. The nanowire's response mechanism to hydrogen peroxide is also discussed in terms of the synergistic activity of the bimetallic binding sites, which has important implications for a better design of functional nanowires as sensing materials for a wide range of applications.
Keywords: Gold–platinum alloy nanowires; Phase structure; Electrocatalytic activity; Hydrogen peroxide sensors
Gold–platinum alloy nanowires as highly sensitive materials for electrochemical detection of hydrogen peroxide by Yibo Zhou; Gang Yu; Fangfang Chang; Bonian Hu; Chuan-Jian Zhong (pp. 56-62).
Display Omitted► An effective strategy is demonstrated for preparing alloy nanowires as sensing materials. ► The alloy nanowires exhibit electrocatalytic activity for the reduction of hydrogen peroxide. ► The alloy nanowires function as an excellent sensor for the detection of hydrogen peroxide. ► The sensor shows a high sensitivity, low detection limit, and fast response time.The exploitation of the unique electrical properties of nanowires requires an effective assembly of nanowires as functional materials on a signal transduction platform. This paper describes a new strategy to assemble gold–platinum alloy nanowires on microelectrode devices and demonstrates the sensing characteristics to hydrogen peroxide. The alloy nanowires have been controllably electrodeposited on microelectrodes by applying an alternating current. The composition, morphology and alloying structures of the nanowires were characterized, revealing a single-phase alloy characteristic, highly monodispersed morphology, and controllable bimetallic compositions. The alloy nanowires were shown to exhibit electrocatalytic response characteristics for the detection of hydrogen peroxide, exhibiting a high sensitivity, low detection limit, and fast response time. The nanowire's response mechanism to hydrogen peroxide is also discussed in terms of the synergistic activity of the bimetallic binding sites, which has important implications for a better design of functional nanowires as sensing materials for a wide range of applications.
Keywords: Gold–platinum alloy nanowires; Phase structure; Electrocatalytic activity; Hydrogen peroxide sensors
Synthesis of cysteamine-coated CdTe quantum dots and its application in mercury (II) detection by Jiying Pei; Hui Zhu; Xiaolei Wang; Hanchang Zhang; Xiurong Yang (pp. 63-68).
Display Omitted► High-quality CA-CdTe QDs were synthesized with a kinetic-growth strategy. ► The synthesis procedures were very simple. ► The obtained QDs were used to detect Hg2+ without the interference of Cu2+.High-quality cysteamine-coated CdTe quantum dots (CA-CdTe QDs) were successfully synthesized in aqueous phase by a facile one-pot method. Through hydroxylamine hydrochloride-promoted kinetic growth strategy, water-soluble CA-CdTe QDs could be obtained conveniently in a conical flask by a stepwise addition of raw materials. The photoluminescence quantum yield (PL QY) of the obtained QDs reached 9.2% at the emission peak of 520nm. The optical property and the morphology of the QDs were characterized by UV–vis absorption spectra, photoluminescence spectra (PL) and transmission electron microscopy (TEM) respectively. Furthermore, the fluorescence of the resultant QDs was quenched by copper (II) (Cu2+) and mercury (II) (Hg2+) meanwhile. It is worthy of note that to separately detect Hg2+, cyanide ion could be used to eliminate the interference of Cu2+. Under the optimal conditions, the response was linearly proportional to the logarithm of Hg2+ concentration over the range of 0.08–3.33μM with a limit of detection (LOD) of 0.07μM.
Keywords: CdTe quantum dots; Cysteamine; Fluorescence quenching; Mercury (II)
Synthesis of cysteamine-coated CdTe quantum dots and its application in mercury (II) detection by Jiying Pei; Hui Zhu; Xiaolei Wang; Hanchang Zhang; Xiurong Yang (pp. 63-68).
Display Omitted► High-quality CA-CdTe QDs were synthesized with a kinetic-growth strategy. ► The synthesis procedures were very simple. ► The obtained QDs were used to detect Hg2+ without the interference of Cu2+.High-quality cysteamine-coated CdTe quantum dots (CA-CdTe QDs) were successfully synthesized in aqueous phase by a facile one-pot method. Through hydroxylamine hydrochloride-promoted kinetic growth strategy, water-soluble CA-CdTe QDs could be obtained conveniently in a conical flask by a stepwise addition of raw materials. The photoluminescence quantum yield (PL QY) of the obtained QDs reached 9.2% at the emission peak of 520nm. The optical property and the morphology of the QDs were characterized by UV–vis absorption spectra, photoluminescence spectra (PL) and transmission electron microscopy (TEM) respectively. Furthermore, the fluorescence of the resultant QDs was quenched by copper (II) (Cu2+) and mercury (II) (Hg2+) meanwhile. It is worthy of note that to separately detect Hg2+, cyanide ion could be used to eliminate the interference of Cu2+. Under the optimal conditions, the response was linearly proportional to the logarithm of Hg2+ concentration over the range of 0.08–3.33μM with a limit of detection (LOD) of 0.07μM.
Keywords: CdTe quantum dots; Cysteamine; Fluorescence quenching; Mercury (II)
Importance of membrane selection in the development of immunochromatographic assays for low-molecular weight compounds by Ji-Ye Lee; Young Ah Kim; Mi Yeon Kim; Yong Tae Lee; Bruce D. Hammock; Hye-Sung Lee (pp. 69-74).
Desirable membrane for competitive immunochromatography.Display Omitted► Membrane selection for competitive immunochromatographic assay (ICA) is discussed. ► Relative migration speed of analyte and antibody-colloidal gold (Ab–CG) is important. ► For lateral flow ICAs, analyte moving slightly faster than Ab–CG is desirable. ► For dipstick ICAs, analyte moving much faster than Ab–CG is desirable. ► The proposal was useful in membrane selection for ICA of the pesticide diazinon.This study was performed to demonstrate the importance of selecting an appropriate membrane when developing immunochromatographic assays (ICAs) for the sensitive detection of low-molecular weight compounds. Based on our findings, we propose a theoretical basis for selecting such a membrane. When eluting the sample solution for the competitive ICA using colloidal gold label for low-molecular analytes, the degree of binding inhibition is proportional to the collision frequency between the antibody-colloidal gold (Ab–CG) and analyte before Ab–CG binding to the capture antigen and a higher concentration of pesticides around the Ab–CG leads to a greater degree of inhibition. Therefore, we propose that the relative migration speed of the analyte and Ab–CG on the test strip is critically important for selecting a membrane in the development of sensitive competitive ICAs. We developed a novel method to estimate such a relative migration speed. We demonstrated the applicability of this proposal by using it to select an appropriate membrane for the development of an ICA of the pesticide diazinon.
Keywords: Immunochromatographic assay; Low-molecular weight compounds; Membrane; Diazinon
Importance of membrane selection in the development of immunochromatographic assays for low-molecular weight compounds by Ji-Ye Lee; Young Ah Kim; Mi Yeon Kim; Yong Tae Lee; Bruce D. Hammock; Hye-Sung Lee (pp. 69-74).
Desirable membrane for competitive immunochromatography.Display Omitted► Membrane selection for competitive immunochromatographic assay (ICA) is discussed. ► Relative migration speed of analyte and antibody-colloidal gold (Ab–CG) is important. ► For lateral flow ICAs, analyte moving slightly faster than Ab–CG is desirable. ► For dipstick ICAs, analyte moving much faster than Ab–CG is desirable. ► The proposal was useful in membrane selection for ICA of the pesticide diazinon.This study was performed to demonstrate the importance of selecting an appropriate membrane when developing immunochromatographic assays (ICAs) for the sensitive detection of low-molecular weight compounds. Based on our findings, we propose a theoretical basis for selecting such a membrane. When eluting the sample solution for the competitive ICA using colloidal gold label for low-molecular analytes, the degree of binding inhibition is proportional to the collision frequency between the antibody-colloidal gold (Ab–CG) and analyte before Ab–CG binding to the capture antigen and a higher concentration of pesticides around the Ab–CG leads to a greater degree of inhibition. Therefore, we propose that the relative migration speed of the analyte and Ab–CG on the test strip is critically important for selecting a membrane in the development of sensitive competitive ICAs. We developed a novel method to estimate such a relative migration speed. We demonstrated the applicability of this proposal by using it to select an appropriate membrane for the development of an ICA of the pesticide diazinon.
Keywords: Immunochromatographic assay; Low-molecular weight compounds; Membrane; Diazinon
A method for the detection of alcohol vapours based on optical sensing of magnesium 5,10,15,20-tetraphenyl porphyrin thin film by an optical spectrometer and principal component analysis by Sumana Kladsomboon; Teerakiat Kerdcharoen (pp. 75-82).
Display Omitted► We prepared magnesium porphyrin thin film as optical sensing materials. ► UV–vis spectrometer was modified to perform as optical artificial nose. ► Change in optical absorption at various spectral regions is used as a sensor array. ► Principal component analysis was employed to discriminate alcohol vapours.In this work we have proposed a method for the detection of alcohol vapours, i.e. methanol, ethanol and isopropanol, based on the optical sensing response of magnesium 5,10,15,20-tetraphenyl porphyrin (MgTPP) thin films, as measured by optical spectrometry with the assistance of chemometric analysis. We have implemented a scheme which allows a laboratory UV–vis spectrometer to act as a so-called “electronic nose” with very little modification. MgTPP thin films were prepared by a spin coating technique, using chloroform as the solvent, and then subjected to thermal annealing at 280°C in an argon atmosphere. These MgTPP optical gas sensors presented significant responses with methanol compared to ethanol and isopropanol, based on the dynamic flow of alcohol vapours at the same mol% of alcohol concentration. Density functional theory (DFT) calculations were performed to model the underlying mechanism of this selectivity. The performance of the optical gas sensors was optimised by varying the fabrication parameters. It is hoped that the MgTPP thin film together with an off-the-shelf optical spectrometer and a simple chemometrics algorithm can be a valuable tool for the analysis of alcoholic content in the beverage industry.
Keywords: Alcohol sensor; Porphyrin; Chemical sensor; Optical sensor
A method for the detection of alcohol vapours based on optical sensing of magnesium 5,10,15,20-tetraphenyl porphyrin thin film by an optical spectrometer and principal component analysis by Sumana Kladsomboon; Teerakiat Kerdcharoen (pp. 75-82).
Display Omitted► We prepared magnesium porphyrin thin film as optical sensing materials. ► UV–vis spectrometer was modified to perform as optical artificial nose. ► Change in optical absorption at various spectral regions is used as a sensor array. ► Principal component analysis was employed to discriminate alcohol vapours.In this work we have proposed a method for the detection of alcohol vapours, i.e. methanol, ethanol and isopropanol, based on the optical sensing response of magnesium 5,10,15,20-tetraphenyl porphyrin (MgTPP) thin films, as measured by optical spectrometry with the assistance of chemometric analysis. We have implemented a scheme which allows a laboratory UV–vis spectrometer to act as a so-called “electronic nose” with very little modification. MgTPP thin films were prepared by a spin coating technique, using chloroform as the solvent, and then subjected to thermal annealing at 280°C in an argon atmosphere. These MgTPP optical gas sensors presented significant responses with methanol compared to ethanol and isopropanol, based on the dynamic flow of alcohol vapours at the same mol% of alcohol concentration. Density functional theory (DFT) calculations were performed to model the underlying mechanism of this selectivity. The performance of the optical gas sensors was optimised by varying the fabrication parameters. It is hoped that the MgTPP thin film together with an off-the-shelf optical spectrometer and a simple chemometrics algorithm can be a valuable tool for the analysis of alcoholic content in the beverage industry.
Keywords: Alcohol sensor; Porphyrin; Chemical sensor; Optical sensor
Capillary column coated with graphene oxide as stationary phase for gas chromatography by Qishu Qu; Yuqi Shen; Chenhao Gu; Zuli Gu; Qian Gu; Chengyin Wang; Xiaoya Hu (pp. 83-87).
Display Omitted► Capillary column was coated with GO via a simple chemical bonding. ► GO coating was used as stationary phase for GC separation. ► Various types of organic compounds were well separated on GO coated column. ► Separation efficiency as high as 1990 theoretical plates per meter for anisole was obtained.The graphene oxide (GO) is carbon based material that has high surface area, high adsorption ability, and is stable at high temperature. In this work, the GO phase was prepared and used for gas chromatographic separation. GO nanosheets were covalently bonded onto the inner surface of fused silica capillary column using 3-aminopropyldiethoxymethyl silane as cross-linking agent. The prepared GO nanosheets were characterized with TEM and the GO coating was characterized with SEM. As a high performance stationary phase, GO provides not only a high surface area to increase the phase ratio but also rich functional groups for the formation of hydrophobicity, hydrogen bonding, and π–π electrostatic stacking interactions with volatile aromatic or unsaturated organic compounds. Thus, mixtures of a wide range of organic compounds including alcohols and aromatic compounds were well separated and an efficiency of 1990 theoretical plates per meter for anisole was obtained on GO coated 1.0m×200μm i.d. fused silica capillary column. The experimental results demonstrate that GO coated capillary columns are promising for gas chromatographic separation.
Keywords: Graphene oxide; Stationary phase; Gas chromatography
Capillary column coated with graphene oxide as stationary phase for gas chromatography by Qishu Qu; Yuqi Shen; Chenhao Gu; Zuli Gu; Qian Gu; Chengyin Wang; Xiaoya Hu (pp. 83-87).
Display Omitted► Capillary column was coated with GO via a simple chemical bonding. ► GO coating was used as stationary phase for GC separation. ► Various types of organic compounds were well separated on GO coated column. ► Separation efficiency as high as 1990 theoretical plates per meter for anisole was obtained.The graphene oxide (GO) is carbon based material that has high surface area, high adsorption ability, and is stable at high temperature. In this work, the GO phase was prepared and used for gas chromatographic separation. GO nanosheets were covalently bonded onto the inner surface of fused silica capillary column using 3-aminopropyldiethoxymethyl silane as cross-linking agent. The prepared GO nanosheets were characterized with TEM and the GO coating was characterized with SEM. As a high performance stationary phase, GO provides not only a high surface area to increase the phase ratio but also rich functional groups for the formation of hydrophobicity, hydrogen bonding, and π–π electrostatic stacking interactions with volatile aromatic or unsaturated organic compounds. Thus, mixtures of a wide range of organic compounds including alcohols and aromatic compounds were well separated and an efficiency of 1990 theoretical plates per meter for anisole was obtained on GO coated 1.0m×200μm i.d. fused silica capillary column. The experimental results demonstrate that GO coated capillary columns are promising for gas chromatographic separation.
Keywords: Graphene oxide; Stationary phase; Gas chromatography