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Analytica Chimica Acta (v.571, #1)
Optimization of LC–MS/MS using triple quadrupole mass analyzer for the simultaneous analysis of carbosulfan and its main metabolites in oranges by Carla Soler; Brett Hamilton; Ambrose Furey; Kevin J. James; Jordi Mañes; Yolanda Picó (pp. 1-11).
This paper describes an analytical method involving a simple solvent extraction for the simultaneous liquid chromatography coupled to quadrupole tandem mass spectrometry (LC–MS/MS) determination of carbosulfan, its most toxic metabolite –carbofuran –, and its other main metabolites – 3-hydroxycarbofuran, 3-ketocarbofuran, 3-hydroxy-7-phenolcarbofuran, 3-keto-7-phenolcarbofuran, 7-phenolcarbofuran and dibutylamine – in oranges. Chromatography was performed on a Zorbax Bonus-RP (150mm×2.1mm, 5μm). The mobile phase was a ternary gradient water–methanol–acetonitrile with 1.0mM ammonium acetate at flow rate of 0.2mlmin−1. The LC separation and MS/MS optimization were studied to select the most appropriate operating conditions. The method developed has also been validated. The limits of quantification (LOQs) were from 1μgkg−1 for carbofuran to 10μgkg−1 for 3-keto-7-phenolcarbofuran. Extracts spiked with carbosulfan and its metabolites, at LOQ level, yielded average recoveries in the range 60–94%, with relative standard deviations (R.S.D.s) less than 15%. Calibration curves for carbosulfan and its metabolites (range LOQ–1000LOQ) were linear, with coefficients of correlations better than 0.990. The method was successfully applied to establish the primary degradation products in oranges treated with carbosulfan. The LC–MS/MS method developed is simple, rapid, and suitable for the quantification and confirmation of carbosulfan and seven of its main metabolites in orange at levels lower than 10μgkg−1.
Keywords: Liquid chromatography–tandem mass spectrometry; Triple quadrupole; Food; Fruits; Pesticides; Metabolites; Carbamates
Optimization of LC–MS/MS using triple quadrupole mass analyzer for the simultaneous analysis of carbosulfan and its main metabolites in oranges by Carla Soler; Brett Hamilton; Ambrose Furey; Kevin J. James; Jordi Mañes; Yolanda Picó (pp. 1-11).
This paper describes an analytical method involving a simple solvent extraction for the simultaneous liquid chromatography coupled to quadrupole tandem mass spectrometry (LC–MS/MS) determination of carbosulfan, its most toxic metabolite –carbofuran –, and its other main metabolites – 3-hydroxycarbofuran, 3-ketocarbofuran, 3-hydroxy-7-phenolcarbofuran, 3-keto-7-phenolcarbofuran, 7-phenolcarbofuran and dibutylamine – in oranges. Chromatography was performed on a Zorbax Bonus-RP (150mm×2.1mm, 5μm). The mobile phase was a ternary gradient water–methanol–acetonitrile with 1.0mM ammonium acetate at flow rate of 0.2mlmin−1. The LC separation and MS/MS optimization were studied to select the most appropriate operating conditions. The method developed has also been validated. The limits of quantification (LOQs) were from 1μgkg−1 for carbofuran to 10μgkg−1 for 3-keto-7-phenolcarbofuran. Extracts spiked with carbosulfan and its metabolites, at LOQ level, yielded average recoveries in the range 60–94%, with relative standard deviations (R.S.D.s) less than 15%. Calibration curves for carbosulfan and its metabolites (range LOQ–1000LOQ) were linear, with coefficients of correlations better than 0.990. The method was successfully applied to establish the primary degradation products in oranges treated with carbosulfan. The LC–MS/MS method developed is simple, rapid, and suitable for the quantification and confirmation of carbosulfan and seven of its main metabolites in orange at levels lower than 10μgkg−1.
Keywords: Liquid chromatography–tandem mass spectrometry; Triple quadrupole; Food; Fruits; Pesticides; Metabolites; Carbamates
Measurement of tobramycin by reversed-phase high-performance liquid chromatography with mass spectrometry detection by Michele Xuemei Guo; Loren Wrisley; Eshwar Maygoo (pp. 12-16).
Analysis of tobramycin faces challenges owing to its significant basicity, hydrophilicity and lack of a UV absorbing chromophore. Chromatographic methods, coupled with derivatization to introduce chromophores for tobramycin analysis, were extensively studied. A direct reversed-phase HPLC method for tobramycin analysis has not been reported. Here, we would like to report a simple LC/MS method for quantitative analysis of tobramycin in pharmaceutical formulations. Reversed-phase HPLC analysis of tobramycin was achieved using a pH stable C18 column with basic (pH 11) aqueous mobile phase (ammonium hydroxide buffer), while direct detection was carried out employing a single quadruple mass detector in negative mode via electrospray ionization. This unique separation–detection combination provided simple and specific determination of tobramycin. This method was found to be linear at a tobramycin concentration range of 0.2–0.8mg/mL with a correlation coefficient value of 0.999. The quantitation limit and detection limit were calculated as 0.210 and 0.063μg/mL, respectively, with 99.994% confidence. This method was successfully applied to measure tobramycin content in matrices containing tobramycin and other pharmaceutical formulation ingredients. Recoveries of 101.8, 97.8 and 106.7% were obtained for tobramycin spiked in the pharmaceutical formulation at concentrations of 1.68, 1.0 and 0.35mg/mL, respectively. The relative standard deviations for six injections of spiked samples ranged from 0.2 to 3.2%, indicating good method repeatability.
Keywords: Tobramycin; Aminoglycoside; pH stable C18 column; HPLC
Measurement of tobramycin by reversed-phase high-performance liquid chromatography with mass spectrometry detection by Michele Xuemei Guo; Loren Wrisley; Eshwar Maygoo (pp. 12-16).
Analysis of tobramycin faces challenges owing to its significant basicity, hydrophilicity and lack of a UV absorbing chromophore. Chromatographic methods, coupled with derivatization to introduce chromophores for tobramycin analysis, were extensively studied. A direct reversed-phase HPLC method for tobramycin analysis has not been reported. Here, we would like to report a simple LC/MS method for quantitative analysis of tobramycin in pharmaceutical formulations. Reversed-phase HPLC analysis of tobramycin was achieved using a pH stable C18 column with basic (pH 11) aqueous mobile phase (ammonium hydroxide buffer), while direct detection was carried out employing a single quadruple mass detector in negative mode via electrospray ionization. This unique separation–detection combination provided simple and specific determination of tobramycin. This method was found to be linear at a tobramycin concentration range of 0.2–0.8mg/mL with a correlation coefficient value of 0.999. The quantitation limit and detection limit were calculated as 0.210 and 0.063μg/mL, respectively, with 99.994% confidence. This method was successfully applied to measure tobramycin content in matrices containing tobramycin and other pharmaceutical formulation ingredients. Recoveries of 101.8, 97.8 and 106.7% were obtained for tobramycin spiked in the pharmaceutical formulation at concentrations of 1.68, 1.0 and 0.35mg/mL, respectively. The relative standard deviations for six injections of spiked samples ranged from 0.2 to 3.2%, indicating good method repeatability.
Keywords: Tobramycin; Aminoglycoside; pH stable C18 column; HPLC
Simultaneous analysis of trans- and cis-isomers of 2-glucosyloxycinnamic acids and coumarin derivatives in Dendrobium thyrsiflorum by high-performance liquid chromatography (HPLC)-photodiode array detection (DAD)-electrospray ionization (ESI)-tandem mass spectrometry (MS) by Guangnong Zhang; Fang Zhang; Li Yang; Enyuan Zhu; Zhengtao Wang; Luoshan Xu; Zhibi Hu (pp. 17-24).
A novel method has been developed for simultaneous analysis for three pairs of trans- and cis-isomers of 2-glucosyloxycinnamic acids, along with their biogenic metabolites (three coumarin derivatives including scopoletin, scoparone and ayapin) in a Chinese medicinal herb Dendrobium thyrsiflorum by using high-performance liquid chromatography (HPLC)-photodiode array detection (DAD)-electrospray ionization (ESI)-tandem mass spectrometry (MS). The method was carried out by using a Polaris C18 column with a gradient solvent system of 0.5% acetic acid aqueous solution–acetonitrile. Seven target analytes including isodensifloside, isothyrsifloside, densifloside, thyrsifloside, scoparone, ayapin and scopoletin were exclusively identified by comparing their retention behaviors, UV and MS spectra with the authentic standards, and their contents in D. thyrsiflorum were simultaneous determined by employing UV detection at 342nm. In addition, another pair of isomers of 2-glucosyloxycinnamic acids was putatively elucidated mainly based on the MS fragmentation. The method was validated and found to be satisfactorily linear, selective and robust. Recoveries ranged from 95.56 to 97.94% for all compounds at three different spiking levels. The limits of detection (LOD) and quantitation (LOQ) ranged, respectively, from 0.02 to 0.13μgmL−1 and 0.07 to 0.39μgmL−1 depending on various compounds. The established quality evaluation method was successfully used for evaluating the quality of D. thyrsiflorum samples of different organs and collections.
Keywords: Dendrobium thyrsiflorum; 2-Glucosyloxycinnamic acid; Coumarin; High-performance liquid chromatography (HPLC)-photodiode array detection (DAD)-electrospray ionization (ESI)-tandem mass spectrometry (MS); Quality evaluation
Simultaneous analysis of trans- and cis-isomers of 2-glucosyloxycinnamic acids and coumarin derivatives in Dendrobium thyrsiflorum by high-performance liquid chromatography (HPLC)-photodiode array detection (DAD)-electrospray ionization (ESI)-tandem mass spectrometry (MS) by Guangnong Zhang; Fang Zhang; Li Yang; Enyuan Zhu; Zhengtao Wang; Luoshan Xu; Zhibi Hu (pp. 17-24).
A novel method has been developed for simultaneous analysis for three pairs of trans- and cis-isomers of 2-glucosyloxycinnamic acids, along with their biogenic metabolites (three coumarin derivatives including scopoletin, scoparone and ayapin) in a Chinese medicinal herb Dendrobium thyrsiflorum by using high-performance liquid chromatography (HPLC)-photodiode array detection (DAD)-electrospray ionization (ESI)-tandem mass spectrometry (MS). The method was carried out by using a Polaris C18 column with a gradient solvent system of 0.5% acetic acid aqueous solution–acetonitrile. Seven target analytes including isodensifloside, isothyrsifloside, densifloside, thyrsifloside, scoparone, ayapin and scopoletin were exclusively identified by comparing their retention behaviors, UV and MS spectra with the authentic standards, and their contents in D. thyrsiflorum were simultaneous determined by employing UV detection at 342nm. In addition, another pair of isomers of 2-glucosyloxycinnamic acids was putatively elucidated mainly based on the MS fragmentation. The method was validated and found to be satisfactorily linear, selective and robust. Recoveries ranged from 95.56 to 97.94% for all compounds at three different spiking levels. The limits of detection (LOD) and quantitation (LOQ) ranged, respectively, from 0.02 to 0.13μgmL−1 and 0.07 to 0.39μgmL−1 depending on various compounds. The established quality evaluation method was successfully used for evaluating the quality of D. thyrsiflorum samples of different organs and collections.
Keywords: Dendrobium thyrsiflorum; 2-Glucosyloxycinnamic acid; Coumarin; High-performance liquid chromatography (HPLC)-photodiode array detection (DAD)-electrospray ionization (ESI)-tandem mass spectrometry (MS); Quality evaluation
The automation of the acquisition and evaluation of pyrolysis-gas chromatography–mass spectrometry data for paint samples by D. Thorburn Burns; K.P. Doolan (pp. 25-29).
The evaluation is described of an automated pyrolysis-gas chromatography–mass spectrometry system combined with a software package to convert total ion current chromatograms into forms that resemble a conventional mass spectra called “spectragrams?. The spectragram for a single paint sample can be “closest fit? matched to a previously created paint pyrogram library via pre-determined target compounds in a handling list. Up to 45 paint samples can be dealt with in an overnight unattended run.
Keywords: Pyrolysis-gas chromatography–mass spectrometry; Automation; Sampling; Data evaluation; Paint; Spectragram
The automation of the acquisition and evaluation of pyrolysis-gas chromatography–mass spectrometry data for paint samples by D. Thorburn Burns; K.P. Doolan (pp. 25-29).
The evaluation is described of an automated pyrolysis-gas chromatography–mass spectrometry system combined with a software package to convert total ion current chromatograms into forms that resemble a conventional mass spectra called “spectragrams”. The spectragram for a single paint sample can be “closest fit” matched to a previously created paint pyrogram library via pre-determined target compounds in a handling list. Up to 45 paint samples can be dealt with in an overnight unattended run.
Keywords: Pyrolysis-gas chromatography–mass spectrometry; Automation; Sampling; Data evaluation; Paint; Spectragram
Monitoring yoctomole alkaline phosphatase by capillary electrophoresis with on-capillary catalysis-electrochemical detection by Xuemei Sun; Ning Gao; Wenrui Jin (pp. 30-33).
An electrophoretically mediated microanalysis method for detection of yoctomole (ymol) alkaline phosphatase (ALP) was developed by a combination of on-capillary enzyme-catalyzed reaction and electrochemical detection. In this method, ALP molecules were electrokinetically injected into a capillary of 10μm i.d. and then electromigrated to the section of the capillary immersed in a warm water bath of 37°C, where ALP reacted for a certain time with disodium phenyl phosphate as the enzyme substrate. ALP could be measured through determining the electroactive product phenol of the enzyme-catalyzed reaction by using electrochemical detection. The phenol concentration was proportional to the mass of ALP. As a catalyst, ALP was not consumed during the reaction, which provided amplification of signal with prolonged the reaction time. In order to enhance the signal-to-noise ratio, the detection end of the capillary was etched to a horn-shape and a single carbon fiber microcylinder electrode of 6μm in diameter as the working electrode was inserted into the detection end of the capillary. Under these conditions, the mass of ALP as low as 1.2×10−22mol (72 molecules) or 4.0×10−23mol (24 molecules) could be detected for the on-capillary reaction time of 15min or 2h.
Keywords: Alkaline phosphatase; Capillary electrophoresis; Enzyme catalysis; Electrochemical detection; Ultratrace analysis
Monitoring yoctomole alkaline phosphatase by capillary electrophoresis with on-capillary catalysis-electrochemical detection by Xuemei Sun; Ning Gao; Wenrui Jin (pp. 30-33).
An electrophoretically mediated microanalysis method for detection of yoctomole (ymol) alkaline phosphatase (ALP) was developed by a combination of on-capillary enzyme-catalyzed reaction and electrochemical detection. In this method, ALP molecules were electrokinetically injected into a capillary of 10μm i.d. and then electromigrated to the section of the capillary immersed in a warm water bath of 37°C, where ALP reacted for a certain time with disodium phenyl phosphate as the enzyme substrate. ALP could be measured through determining the electroactive product phenol of the enzyme-catalyzed reaction by using electrochemical detection. The phenol concentration was proportional to the mass of ALP. As a catalyst, ALP was not consumed during the reaction, which provided amplification of signal with prolonged the reaction time. In order to enhance the signal-to-noise ratio, the detection end of the capillary was etched to a horn-shape and a single carbon fiber microcylinder electrode of 6μm in diameter as the working electrode was inserted into the detection end of the capillary. Under these conditions, the mass of ALP as low as 1.2×10−22mol (72 molecules) or 4.0×10−23mol (24 molecules) could be detected for the on-capillary reaction time of 15min or 2h.
Keywords: Alkaline phosphatase; Capillary electrophoresis; Enzyme catalysis; Electrochemical detection; Ultratrace analysis
Enhancing deoxyribonucleic acid (DNA) detection sensitivity through microconcentration on patterned fluorocarbon polymer surface by Jiong Li; Yijin Wang; Zuhong Lu; Mansun Chan (pp. 34-39).
A microconcentration concept is proposed to enhance the sensitivity of deoxyribonucleic acid (DNA) hybridization due to evaporation of the hybridization solution on a patterned hydrophobic fluorocarbon polymer (FCP) surface. The combination of microconcentration and hybridization processes provides a tool to manipulate nanoliter solution. To fabricate a patterned DNA microarray with hydrophobic surrounding surface, a plasma polymerization and lift-off protocol was designed so that the process can be carried out in a standard microelectronic fabrication laboratory with minimal adjustments on the equipment. After microconcentration, a 1μL hybridization solution can be concentrated to below 10nL, which improves the hybridization sensitivity by a factor of 100.
Keywords: Deoxyribonucleic acid (DNA) detection; Sensitivity; Microconcentration; Patterning; Hydrophobic surface
Enhancing deoxyribonucleic acid (DNA) detection sensitivity through microconcentration on patterned fluorocarbon polymer surface by Jiong Li; Yijin Wang; Zuhong Lu; Mansun Chan (pp. 34-39).
A microconcentration concept is proposed to enhance the sensitivity of deoxyribonucleic acid (DNA) hybridization due to evaporation of the hybridization solution on a patterned hydrophobic fluorocarbon polymer (FCP) surface. The combination of microconcentration and hybridization processes provides a tool to manipulate nanoliter solution. To fabricate a patterned DNA microarray with hydrophobic surrounding surface, a plasma polymerization and lift-off protocol was designed so that the process can be carried out in a standard microelectronic fabrication laboratory with minimal adjustments on the equipment. After microconcentration, a 1μL hybridization solution can be concentrated to below 10nL, which improves the hybridization sensitivity by a factor of 100.
Keywords: Deoxyribonucleic acid (DNA) detection; Sensitivity; Microconcentration; Patterning; Hydrophobic surface
Solid phase microextraction and gas chromatography with ion trap detector (GC-ITD) analysis of amitraz residues in beeswax after hydrolysis to 2,4-dimethylaniline by Jan Lení?ek; Milan Sekyra; Andrea Rychtecká Novotná; Eva Vášová; Dalibor Titěra; Vladimír Veselý (pp. 40-44).
An analytical method for the determination of amitraz residues in beeswax after hydrolysis to 2,4-dimethylaniline is reported. It consists of wax extraction with an acid buffer solution, head space solid phase microextraction and GC-ITD analysis. The limit of determination is 1ngg−1. Wax samples from beekepers and commercial foundations were analysed, content of residues varied from <1 to 20.5ngg−1.
Keywords: 2,4-Dimethylaniline; Amitraz; Beeswax; SPME; GC-ITDAbbreviations; DMA; 2,4-dimethylaniline; DMF; 2,4-dimethylformanilide; DPMF; N; -(2,4-dimethylphenyl)-; N; ′-methylformamidine; GC-ECD; gas chromatography with electron capture detector; GC-ITD; gas chromatography with ion trap detector; PDMS; polydimethylsiloxane; R.S.D.; relative standard deviation; SPME; solid phase microextraction; LOD; limit of detection; LOQ; limit of quantification
Solid phase microextraction and gas chromatography with ion trap detector (GC-ITD) analysis of amitraz residues in beeswax after hydrolysis to 2,4-dimethylaniline by Jan Leníček; Milan Sekyra; Andrea Rychtecká Novotná; Eva Vášová; Dalibor Titěra; Vladimír Veselý (pp. 40-44).
An analytical method for the determination of amitraz residues in beeswax after hydrolysis to 2,4-dimethylaniline is reported. It consists of wax extraction with an acid buffer solution, head space solid phase microextraction and GC-ITD analysis. The limit of determination is 1ngg−1. Wax samples from beekepers and commercial foundations were analysed, content of residues varied from <1 to 20.5ngg−1.
Keywords: 2,4-Dimethylaniline; Amitraz; Beeswax; SPME; GC-ITDAbbreviations; DMA; 2,4-dimethylaniline; DMF; 2,4-dimethylformanilide; DPMF; N; -(2,4-dimethylphenyl)-; N; ′-methylformamidine; GC-ECD; gas chromatography with electron capture detector; GC-ITD; gas chromatography with ion trap detector; PDMS; polydimethylsiloxane; R.S.D.; relative standard deviation; SPME; solid phase microextraction; LOD; limit of detection; LOQ; limit of quantification
Silicone glue coated stainless steel wire for solid phase microextraction by Dalia Panavaitė; Audrius Padarauskas; Vida Vi?ka?kaitė (pp. 45-50).
A new solid phase microextraction (SPME) fiber based on high-temperature silicone glue coated on a stainless steel wire is presented. The fiber coating can be prepared easily in a few minutes, it is mechanically stable and exhibits relatively high thermal stability (up to 260°C). The extraction properties of the fiber to benzene, toluene, ethylbenzene, and xylenes (BTEX) were examined using both direct and headspace SPME modes coupled to gas chromatography-flame ionization detection. The effects of the extraction and desorption parameters including extraction and desorption time, sampling and desorption temperature, and ionic strength on the extraction/desorption efficiency have been studied. For both headspace and direct SPME the calibration graphs were linear in the concentration range from 0.5μgL−1 to 10mgL−1 ( R2>0.996) and detection limits ranged from 0.07 to 0.24μgL−1. Single fiber repeatability and fiber-to-fiber reproducibility were less than 6.8 and 21.5%, respectively. Finally, headspace SPME was applied to determine BTEX in petrol station waste waters with spiked recoveries in the range of 89.7–105.2%.
Keywords: Solid phase microextraction; Silicone glue coating; Gas chromatography; Benzene; Toluene; Ethylbenzene; Xylenes
Silicone glue coated stainless steel wire for solid phase microextraction by Dalia Panavaitė; Audrius Padarauskas; Vida Vičkačkaitė (pp. 45-50).
A new solid phase microextraction (SPME) fiber based on high-temperature silicone glue coated on a stainless steel wire is presented. The fiber coating can be prepared easily in a few minutes, it is mechanically stable and exhibits relatively high thermal stability (up to 260°C). The extraction properties of the fiber to benzene, toluene, ethylbenzene, and xylenes (BTEX) were examined using both direct and headspace SPME modes coupled to gas chromatography-flame ionization detection. The effects of the extraction and desorption parameters including extraction and desorption time, sampling and desorption temperature, and ionic strength on the extraction/desorption efficiency have been studied. For both headspace and direct SPME the calibration graphs were linear in the concentration range from 0.5μgL−1 to 10mgL−1 ( R2>0.996) and detection limits ranged from 0.07 to 0.24μgL−1. Single fiber repeatability and fiber-to-fiber reproducibility were less than 6.8 and 21.5%, respectively. Finally, headspace SPME was applied to determine BTEX in petrol station waste waters with spiked recoveries in the range of 89.7–105.2%.
Keywords: Solid phase microextraction; Silicone glue coating; Gas chromatography; Benzene; Toluene; Ethylbenzene; Xylenes
Microwave assisted micellar extraction coupled with solid phase microextraction for the determination of organochlorine pesticides in soil samples by Daura Vega Moreno; Zoraida Sosa Ferrera; José J. Santana Rodríguez (pp. 51-57).
Microwave assisted micellar extraction (MAME) coupled with solid phase microextraction (SPME) and HPLC-UV determination have been used for the determination of five organochlorine pesticides from agricultural soil samples. A non-ionic surfactant, Polyoxyethlylene 10 Lauryl Ether was used, and the different variables for the optimization of MAME and SPME procedures were studied. This method was applied successfully to the determination of these pesticides in several kinds of agricultural soil samples with different characteristics. Most of the compounds studied can be recovered in good yields with R.S.D. lower than 9% and detection limit ranged between 56–96ngg−1 for the pesticides studied.
Keywords: Organochlorine pesticides; Micellar medium; Extraction methods; Microwave; Solid phase microextraction; Soils; High performance liquid chromatography
Microwave assisted micellar extraction coupled with solid phase microextraction for the determination of organochlorine pesticides in soil samples by Daura Vega Moreno; Zoraida Sosa Ferrera; José J. Santana Rodríguez (pp. 51-57).
Microwave assisted micellar extraction (MAME) coupled with solid phase microextraction (SPME) and HPLC-UV determination have been used for the determination of five organochlorine pesticides from agricultural soil samples. A non-ionic surfactant, Polyoxyethlylene 10 Lauryl Ether was used, and the different variables for the optimization of MAME and SPME procedures were studied. This method was applied successfully to the determination of these pesticides in several kinds of agricultural soil samples with different characteristics. Most of the compounds studied can be recovered in good yields with R.S.D. lower than 9% and detection limit ranged between 56–96ngg−1 for the pesticides studied.
Keywords: Organochlorine pesticides; Micellar medium; Extraction methods; Microwave; Solid phase microextraction; Soils; High performance liquid chromatography
A new analytical application of nylon-induced room-temperature phosphorescence: Determination of thiabendazole in water samples by R.A. Correa; G.M. Escandar (pp. 58-65).
This paper discusses the first analytical determination of the widely used fungicide thiabendazole by nylon-induced phosphorimetry. Nylon was investigated as a novel solid-matrix for inducing room-temperature phosphorescence of thiabendazole, which was enhanced under the effect of external heavy-atom salts. Among the investigated salts, lead(II) acetate was the most effective in yielding a high phosphorescence signal. An additional enhancement of the phosphorescence emission was attained when the measurements were carried out under a nitrogen atmosphere. There was only a moderate increase in the presence of cyclodextrins. The room-temperature phosphorescence lifetimes of the adsorbed thiabendazole were measured under different working conditions and, in all cases, two decaying components were detected. On the basis of the obtained results, a very simple and sensitive phosphorimetric method for the determination of thiabendazole was established. The analytical figures of merit obtained under the best experimental conditions were: linear calibration range from 0.031 to 0.26μgml−1 (the lowest value corresponds to the quantitation limit), relative standard deviation, 2.4% ( n=5) at a level of 0.096μgml−1, and limit of detection calculated according to 1995 IUPAC Recommendations equal to 0.010μgml−1 (0.03ng/spot). The potential interference from common agrochemicals was also studied. The feasibility of determining thiabendazole in real samples was successfully evaluated through the analysis of spiked river, tap and mineral water samples.
Keywords: Solid-surface room-temperature phosphorimetry; Nylon membrane; Thiabendazole
A new analytical application of nylon-induced room-temperature phosphorescence: Determination of thiabendazole in water samples by R.A. Correa; G.M. Escandar (pp. 58-65).
This paper discusses the first analytical determination of the widely used fungicide thiabendazole by nylon-induced phosphorimetry. Nylon was investigated as a novel solid-matrix for inducing room-temperature phosphorescence of thiabendazole, which was enhanced under the effect of external heavy-atom salts. Among the investigated salts, lead(II) acetate was the most effective in yielding a high phosphorescence signal. An additional enhancement of the phosphorescence emission was attained when the measurements were carried out under a nitrogen atmosphere. There was only a moderate increase in the presence of cyclodextrins. The room-temperature phosphorescence lifetimes of the adsorbed thiabendazole were measured under different working conditions and, in all cases, two decaying components were detected. On the basis of the obtained results, a very simple and sensitive phosphorimetric method for the determination of thiabendazole was established. The analytical figures of merit obtained under the best experimental conditions were: linear calibration range from 0.031 to 0.26μgml−1 (the lowest value corresponds to the quantitation limit), relative standard deviation, 2.4% ( n=5) at a level of 0.096μgml−1, and limit of detection calculated according to 1995 IUPAC Recommendations equal to 0.010μgml−1 (0.03ng/spot). The potential interference from common agrochemicals was also studied. The feasibility of determining thiabendazole in real samples was successfully evaluated through the analysis of spiked river, tap and mineral water samples.
Keywords: Solid-surface room-temperature phosphorimetry; Nylon membrane; Thiabendazole
Automated flow fluorescent immunoassay for part per trillion detection of the neonicotinoid insecticide thiamethoxam by Hee-Joo Kim; Weilin L. Shelver; Eul-Chul Hwang; Ting Xu; Qing X. Li (pp. 66-73).
An ultra sensitive automated flow fluorescent immunoassay was developed using the KinExA™ 3000 system for quantitative analysis of the neonicotinoid insecticide thiamethoxam. Five new monoclonal antibodies were obtained and screened with a competitive ELISA. One monoclonal antibody designated as E6VI was evaluated for sensitivity, selectivity and solvent tolerance with the KinExA. Sensitivity determined from the concentration of half-maximal inhibition (IC50) was obtained by plotting KinExA signals to a four-parameter sigmoidal curve as a function of analyte concentrations. For the most sensitive clone, the IC50 and the limit of detection were approximately 30pgml−1 and 16pgml−1, respectively. Cross-reactivity was estimated by measuring the equilibrium constants ( Kd) for four other neonicotinoid insecticides (clothianidin, imidacloprid, dinotefuran, and acetamiprid). E6VI was very specific to thiamethoxam with <0.11% cross-reactivity for tested neonicotinoids. An excellent correlation ( r2=0.99) was obtained between spiked and measured concentrations of thiamethoxam in stream and tap water, potato, cucumber, and apple samples.
Keywords: Thiamethoxam; Kinetic exclusion assay; KinExA; Immunoassay; ELISA; Insecticide
Automated flow fluorescent immunoassay for part per trillion detection of the neonicotinoid insecticide thiamethoxam by Hee-Joo Kim; Weilin L. Shelver; Eul-Chul Hwang; Ting Xu; Qing X. Li (pp. 66-73).
An ultra sensitive automated flow fluorescent immunoassay was developed using the KinExA™ 3000 system for quantitative analysis of the neonicotinoid insecticide thiamethoxam. Five new monoclonal antibodies were obtained and screened with a competitive ELISA. One monoclonal antibody designated as E6VI was evaluated for sensitivity, selectivity and solvent tolerance with the KinExA. Sensitivity determined from the concentration of half-maximal inhibition (IC50) was obtained by plotting KinExA signals to a four-parameter sigmoidal curve as a function of analyte concentrations. For the most sensitive clone, the IC50 and the limit of detection were approximately 30pgml−1 and 16pgml−1, respectively. Cross-reactivity was estimated by measuring the equilibrium constants ( Kd) for four other neonicotinoid insecticides (clothianidin, imidacloprid, dinotefuran, and acetamiprid). E6VI was very specific to thiamethoxam with <0.11% cross-reactivity for tested neonicotinoids. An excellent correlation ( r2=0.99) was obtained between spiked and measured concentrations of thiamethoxam in stream and tap water, potato, cucumber, and apple samples.
Keywords: Thiamethoxam; Kinetic exclusion assay; KinExA; Immunoassay; ELISA; Insecticide
Ultrasensitive detection of pepsinogen I and pepsinogen II by a time-resolved fluoroimmunoassay and its preliminary clinical applications by Biao Huang; Hualong Xiao; Xiangrui Zhang; Lan Zhu; Haiyan Liu; Jian Jin (pp. 74-78).
A fast and highly sensitive assay for pepsinogen I (PG I) and pepsinogen II (PG II) by using time-resolved fluoroimmunoassay (TRFIA) detection technique has been developed for the determination of serum PG I and PG II against gastrointestinal diseases. On the noncompetitive assay, one monoclonal antibody (McAb) coated on wells was directed against a specific antigenic site on the PG I or PG II. The McAb, called as labelling McAb, was prepared with the europium-chelate of N-( p-isothiocyanatobenzyl)-diethylenetriamine- N, N, N, N-tetraacetic acid and directed against a different antigenic site on the PG I or PG II molecule. After bound/free separation by washing, the fluorescence counts of bound Eu3+–McAb were measured. The levels of PG in sera from patients or healthy volunteers were determined by PG I and PG II TRFIA using the autoDELFIA1235 system. The measurement ranges of PG I-TRFIA were 3.5–328.0μgL−1 and those of PG II-TRFIA were 2.0–55.0μgL−1. The within-run and between-run CVs of the PG I-TRFIA were 1.9% and 4.7%, respectively, and those of PG II-TRFIA were 2.1% and 3.8%, respectively. The recovery rates of PG I-TRFIA and PG II-TRFIA were 102.7% and 104.6%, respectively. The detection limitations of PG I and PG II were 0.05μgL−1 and 0.02μgL−1, respectively. The dilution experiments showed the percentage of expected value of PG I-TRFIA was 93.2–102.3% and of PG II-TRFIA was 97.3–110.6%. The cross-reacting rate between PG I and PG II was negligible. The linear correlation of radioimmunoassay (RIA) and TRFIA measurements resulted in a correlation coefficient as 0.926 of PG I and as 0.959 of PG II. The europium-labelling McAbs were stable for at least one year at −20°C, and the results of the TRFIA with same reagents were reproducible over one year as well. The means of 1600 healthy volunteers were 162.4±52.1μgL−1 for serum PG I, 11.7±6.8μgL−1 for serum PG II, and 13.8±7.4 for the PG I/PG II ratio. The normal ranges of Serum PG I levels for healthy volunteers were 58.2–266.6μgL−1, and those of serum PG II levels were less than 25.3μgL−1. The availability of a highly sensitive, reliable, and convenient PG-TRFIA method for quantifying PG will allow investigations into the possible diagnostic value of this analysis in various clinical conditions, including gastric carcinoma, duodenal ulcer, gastric ulcer and gastritis. The sensitivity and reproducibility of the assay were satisfactory for clinical applications.
Keywords: Time-resolved fluoroimmunoassay (TRFIA); Pepsinogen I; Pepsinogen II; Monoclonal antibody; Analysis
Ultrasensitive detection of pepsinogen I and pepsinogen II by a time-resolved fluoroimmunoassay and its preliminary clinical applications by Biao Huang; Hualong Xiao; Xiangrui Zhang; Lan Zhu; Haiyan Liu; Jian Jin (pp. 74-78).
A fast and highly sensitive assay for pepsinogen I (PG I) and pepsinogen II (PG II) by using time-resolved fluoroimmunoassay (TRFIA) detection technique has been developed for the determination of serum PG I and PG II against gastrointestinal diseases. On the noncompetitive assay, one monoclonal antibody (McAb) coated on wells was directed against a specific antigenic site on the PG I or PG II. The McAb, called as labelling McAb, was prepared with the europium-chelate of N-( p-isothiocyanatobenzyl)-diethylenetriamine- N, N, N, N-tetraacetic acid and directed against a different antigenic site on the PG I or PG II molecule. After bound/free separation by washing, the fluorescence counts of bound Eu3+–McAb were measured. The levels of PG in sera from patients or healthy volunteers were determined by PG I and PG II TRFIA using the autoDELFIA1235 system. The measurement ranges of PG I-TRFIA were 3.5–328.0μgL−1 and those of PG II-TRFIA were 2.0–55.0μgL−1. The within-run and between-run CVs of the PG I-TRFIA were 1.9% and 4.7%, respectively, and those of PG II-TRFIA were 2.1% and 3.8%, respectively. The recovery rates of PG I-TRFIA and PG II-TRFIA were 102.7% and 104.6%, respectively. The detection limitations of PG I and PG II were 0.05μgL−1 and 0.02μgL−1, respectively. The dilution experiments showed the percentage of expected value of PG I-TRFIA was 93.2–102.3% and of PG II-TRFIA was 97.3–110.6%. The cross-reacting rate between PG I and PG II was negligible. The linear correlation of radioimmunoassay (RIA) and TRFIA measurements resulted in a correlation coefficient as 0.926 of PG I and as 0.959 of PG II. The europium-labelling McAbs were stable for at least one year at −20°C, and the results of the TRFIA with same reagents were reproducible over one year as well. The means of 1600 healthy volunteers were 162.4±52.1μgL−1 for serum PG I, 11.7±6.8μgL−1 for serum PG II, and 13.8±7.4 for the PG I/PG II ratio. The normal ranges of Serum PG I levels for healthy volunteers were 58.2–266.6μgL−1, and those of serum PG II levels were less than 25.3μgL−1. The availability of a highly sensitive, reliable, and convenient PG-TRFIA method for quantifying PG will allow investigations into the possible diagnostic value of this analysis in various clinical conditions, including gastric carcinoma, duodenal ulcer, gastric ulcer and gastritis. The sensitivity and reproducibility of the assay were satisfactory for clinical applications.
Keywords: Time-resolved fluoroimmunoassay (TRFIA); Pepsinogen I; Pepsinogen II; Monoclonal antibody; Analysis
Comparison between conventional indirect competitive enzyme-linked immunosorbent assay (icELISA) and simplified icELISA for small molecules by Jing Zhao; Gang Li; Guo-Xiang Yi; Bao-Min Wang; Ai-Xing Deng; Tie-Gui Nan; Zhao-Hu Li; Qing X. Li (pp. 79-85).
A simplified indirect competitive enzyme-linked immunosorbent assay (icELISA) for small molecules was established by modifying the procedure of conventional icELISA. The key change was that the analyte, antibody, and enzyme-labeled second antibody in the simplified icELISA were added in one step, whereas in conventional icELISA these reagents were added in two separate steps. Three small chemicals, namely zeatin riboside, glycyrrhetinic acid, and chlorimuron-ethyl, were used to verify the new assay format and compare the results obtained from conventional icELISA and simplified icELISA. The results indicated that, under optimized conditions, the new assay offered several advantages over the conventional icELISA, which are simpler, less time consuming and higher sensitive although it requires more amount of reagents. The assay sensitivity (IC50) was improved for 1.2–1.4-fold. Four licorice roots samples were analyzed by conventional icELISA and simplified icELISA, as well as liquid chromatography (LC). There was no significant difference among the content obtained from the three methods for each sample. The correlation between data obtained from conventional icELISA and simplified icELISA analyses was 0.9888. The results suggest that the simplified icELISA be useful for high throughput screening of small molecules.
Keywords: icELISA; Small molecules; Chlorimuron-ethyl; Glycyrrhetinic acid; Zeatin riboside
Comparison between conventional indirect competitive enzyme-linked immunosorbent assay (icELISA) and simplified icELISA for small molecules by Jing Zhao; Gang Li; Guo-Xiang Yi; Bao-Min Wang; Ai-Xing Deng; Tie-Gui Nan; Zhao-Hu Li; Qing X. Li (pp. 79-85).
A simplified indirect competitive enzyme-linked immunosorbent assay (icELISA) for small molecules was established by modifying the procedure of conventional icELISA. The key change was that the analyte, antibody, and enzyme-labeled second antibody in the simplified icELISA were added in one step, whereas in conventional icELISA these reagents were added in two separate steps. Three small chemicals, namely zeatin riboside, glycyrrhetinic acid, and chlorimuron-ethyl, were used to verify the new assay format and compare the results obtained from conventional icELISA and simplified icELISA. The results indicated that, under optimized conditions, the new assay offered several advantages over the conventional icELISA, which are simpler, less time consuming and higher sensitive although it requires more amount of reagents. The assay sensitivity (IC50) was improved for 1.2–1.4-fold. Four licorice roots samples were analyzed by conventional icELISA and simplified icELISA, as well as liquid chromatography (LC). There was no significant difference among the content obtained from the three methods for each sample. The correlation between data obtained from conventional icELISA and simplified icELISA analyses was 0.9888. The results suggest that the simplified icELISA be useful for high throughput screening of small molecules.
Keywords: icELISA; Small molecules; Chlorimuron-ethyl; Glycyrrhetinic acid; Zeatin riboside
Advantages of using a mercury coated, micro-wire, electrode in adsorptive cathodic stripping voltammetry by Jenny Gun; Pascal Salaün; Constant M.G. van den Berg (pp. 86-92).
A mercury coated, gold, micro-wire electrode is used here for the determination of iron in seawater by catalytic cathodic stripping voltammetry (CSV) with a limit of detection of 0.1nM Fe at a 60s adsorption time. It was found that the electrode surface is stable for extended periods of analyses (at least five days) and that it is reactivated by briefly (2s) applying a negative potential prior to each scan. Advantages of this electrode over mercury drop electrodes are that metallic mercury use is eliminated and that it can be readily used for flow analysis. This is demonstrated here by the determination of iron in seawater by continuous flow analysis. It is likely that this method can be extended to other elements. Experiments using bismuth coated, carbon fibre, electrodes showed that the bismuth catalyses the oxidation of the important oxidants bromate and hydrogen peroxide, which makes it impossible to use bismuth based electrodes for catalytic CSV involving these oxidants. For this reason mercury coated electrodes retain a major advantage for catalytic voltammetric analyses.
Keywords: Cathodic stripping voltammetry; Microelectrode; Iron; Seawater
Advantages of using a mercury coated, micro-wire, electrode in adsorptive cathodic stripping voltammetry by Jenny Gun; Pascal Salaün; Constant M.G. van den Berg (pp. 86-92).
A mercury coated, gold, micro-wire electrode is used here for the determination of iron in seawater by catalytic cathodic stripping voltammetry (CSV) with a limit of detection of 0.1nM Fe at a 60s adsorption time. It was found that the electrode surface is stable for extended periods of analyses (at least five days) and that it is reactivated by briefly (2s) applying a negative potential prior to each scan. Advantages of this electrode over mercury drop electrodes are that metallic mercury use is eliminated and that it can be readily used for flow analysis. This is demonstrated here by the determination of iron in seawater by continuous flow analysis. It is likely that this method can be extended to other elements. Experiments using bismuth coated, carbon fibre, electrodes showed that the bismuth catalyses the oxidation of the important oxidants bromate and hydrogen peroxide, which makes it impossible to use bismuth based electrodes for catalytic CSV involving these oxidants. For this reason mercury coated electrodes retain a major advantage for catalytic voltammetric analyses.
Keywords: Cathodic stripping voltammetry; Microelectrode; Iron; Seawater
Fast ultrasound-assisted treatment of urine samples for chronopotentiometric stripping determination of mercury at gold film electrodes by Rodrigo A.A. Munoz; Fabiana S. Felix; Márcio A. Augelli; Thelma Pavesi; Lucio Angnes (pp. 93-98).
This work describes an efficient, fast, and reliable analytical methodology for mercury determination in urine samples using stripping chronopotentiometry at gold film electrodes. The samples were sonicated in the presence of concentrated HC1 and H2O2 for 15min in order to disrupt the organic ligands and release the mercury. Thirty samples can be treated over the optimized region of the ultrasonic bath. This sample preparation was enough to allow the accurate stripping chronopotentiometric determination of mercury in the treated samples. No background currents and no passivation of the gold film electrode due to the sample matrix were verified. The samples were also analyzed by cold vapour atomic absorption spectrometry (CV-AAS) and good agreement between the results was verified. The analysis of NIST SRM 2670 (Toxic Metals in Freeze-Dried Urine) also validated the proposed electroanalytical method. Finally, this method was applied for mercury evaluation in urine of workers exposed to hospital waste incinerators.
Keywords: Ultrasound-assisted treatment; Ultrasonic bath; Stripping chronopotentiometry; Mercury; Gold film electrode; Urine
Fast ultrasound-assisted treatment of urine samples for chronopotentiometric stripping determination of mercury at gold film electrodes by Rodrigo A.A. Munoz; Fabiana S. Felix; Márcio A. Augelli; Thelma Pavesi; Lucio Angnes (pp. 93-98).
This work describes an efficient, fast, and reliable analytical methodology for mercury determination in urine samples using stripping chronopotentiometry at gold film electrodes. The samples were sonicated in the presence of concentrated HC1 and H2O2 for 15min in order to disrupt the organic ligands and release the mercury. Thirty samples can be treated over the optimized region of the ultrasonic bath. This sample preparation was enough to allow the accurate stripping chronopotentiometric determination of mercury in the treated samples. No background currents and no passivation of the gold film electrode due to the sample matrix were verified. The samples were also analyzed by cold vapour atomic absorption spectrometry (CV-AAS) and good agreement between the results was verified. The analysis of NIST SRM 2670 (Toxic Metals in Freeze-Dried Urine) also validated the proposed electroanalytical method. Finally, this method was applied for mercury evaluation in urine of workers exposed to hospital waste incinerators.
Keywords: Ultrasound-assisted treatment; Ultrasonic bath; Stripping chronopotentiometry; Mercury; Gold film electrode; Urine
Application of adsorptive stripping voltammetry to the simultaneous determination of bismuth and copper in the presence of nuclear fast red by M.B. Gholivand; A.A. Romiani (pp. 99-104).
A sensitive and selective method for the simultaneous determination of copper and bismuth by adsorptive stripping was developed using nuclear fast red (2-anthracenesulfonic acid, 4-amino-9,10-dihydro-1,3-dihydroxy-9,10-dioxo-, monosodium salt) as selective complexing agent onto hanging mercury drop electrode. In a single scan both metals gave peaks that were distinctly separated by 85mV allowing their determination in the presence of each other. Optimal analytical conditions were found to be: nuclear fast red concentration of 80μM, pH of 2.8 and adsorptive potential of −300mV versus Ag/AgCl. With accumulation time of 180s the peaks currents are proportional to concentration of copper and bismuth over the 1–100 and 5–60ngmL−1 range with detection limits of 0.2 and 1.2ngmL−1, respectively. The procedure was applied to simultaneous determination of copper and bismuth in some real samples.
Keywords: Copper and bismuth; Adsorptive stripping voltammetry; Nuclear fast red; Simultaneous determination
Application of adsorptive stripping voltammetry to the simultaneous determination of bismuth and copper in the presence of nuclear fast red by M.B. Gholivand; A.A. Romiani (pp. 99-104).
A sensitive and selective method for the simultaneous determination of copper and bismuth by adsorptive stripping was developed using nuclear fast red (2-anthracenesulfonic acid, 4-amino-9,10-dihydro-1,3-dihydroxy-9,10-dioxo-, monosodium salt) as selective complexing agent onto hanging mercury drop electrode. In a single scan both metals gave peaks that were distinctly separated by 85mV allowing their determination in the presence of each other. Optimal analytical conditions were found to be: nuclear fast red concentration of 80μM, pH of 2.8 and adsorptive potential of −300mV versus Ag/AgCl. With accumulation time of 180s the peaks currents are proportional to concentration of copper and bismuth over the 1–100 and 5–60ngmL−1 range with detection limits of 0.2 and 1.2ngmL−1, respectively. The procedure was applied to simultaneous determination of copper and bismuth in some real samples.
Keywords: Copper and bismuth; Adsorptive stripping voltammetry; Nuclear fast red; Simultaneous determination
Influence of the physical properties and handling of silica gel modified carbon paste electrodes on the phase transfer of solved Cu(II) ions by Axel Meyer; Susanne Höffler; Klaus Fischer (pp. 105-112).
Carbon paste electrodes (CPE) modified with natural minerals might be utilised to mimic adsorption/desorption reactions at natural interfaces. As a step towards this aim, several properties and application conditions of CPEs, modified with silica gel, were tested for their influence on phase transfer reactions of solved Cu(II)–tetrammine complex ions.The peak current recorded during the anodic stripping of adsorbed Cu(II) species increased with increasing diameter of the circular electrode surface. A silica gel content of 29 mass percent yielded the highest peak current at otherwise constant exposition conditions. A substitution of graphite by glassy carbon did not enhance the electrode sensitivity. The peak current increased with increasing exposition time (up to 20min) and with decreasing size of the modifier particles. Typically between 12% and 22% of the solved Cu ions were adsorbed onto the electrode surface and between 15% and 20% of this Cu fraction was subsequently removed by stripping and electrode regeneration. Despite the incomplete electrode regeneration the mass transfer ratios of the Cu(II) species were relatively constant during several application cycles.
Keywords: Silica gel modified carbon paste electrode; Adsorption; Desorption; Phase distribution; Copper(II) ions; Cu(II)–tetrammine complex; Voltammetry
Influence of the physical properties and handling of silica gel modified carbon paste electrodes on the phase transfer of solved Cu(II) ions by Axel Meyer; Susanne Höffler; Klaus Fischer (pp. 105-112).
Carbon paste electrodes (CPE) modified with natural minerals might be utilised to mimic adsorption/desorption reactions at natural interfaces. As a step towards this aim, several properties and application conditions of CPEs, modified with silica gel, were tested for their influence on phase transfer reactions of solved Cu(II)–tetrammine complex ions.The peak current recorded during the anodic stripping of adsorbed Cu(II) species increased with increasing diameter of the circular electrode surface. A silica gel content of 29 mass percent yielded the highest peak current at otherwise constant exposition conditions. A substitution of graphite by glassy carbon did not enhance the electrode sensitivity. The peak current increased with increasing exposition time (up to 20min) and with decreasing size of the modifier particles. Typically between 12% and 22% of the solved Cu ions were adsorbed onto the electrode surface and between 15% and 20% of this Cu fraction was subsequently removed by stripping and electrode regeneration. Despite the incomplete electrode regeneration the mass transfer ratios of the Cu(II) species were relatively constant during several application cycles.
Keywords: Silica gel modified carbon paste electrode; Adsorption; Desorption; Phase distribution; Copper(II) ions; Cu(II)–tetrammine complex; Voltammetry
Application of band-target entropy minimization (BTEM) and residual spectral analysis to in situ reflection–absorption infrared spectroscopy (RAIRS) data from surface chemistry studies by Boon Hong Kee; Wee-Sun Sim; Wee Chew (pp. 113-120).
The band-target entropy minimization (BTEM) curve resolution technique has been used to analyze in situ reflection–absorption infrared spectroscopy (RAIRS) data of CO chemisorption on Ni(111) single crystal surfaces. The bilinearity assumption for pRAIRS data, that is, negative logarithm to the base 10 of raw reflectance RAIRS data, was found to be sufficiently valid for the test data. A total of 11 real pure component pRAIRS spectra were elucidated via BTEM in tandem with an iterative residual spectral data analysis. Furthermore, 2 abstract pure component right singular vectors were found to account for all the pRAIRS non-linearities, baseline drifts and other spectral noise. In total, 100.2% of the pRAIRS signals were accounted for by these 13 spectral components. The 11 real pure component pRAIRS spectra and their corresponding relative concentration kinetic sequences correlate with 6 well-known adsorbed CO domain structures. Moreover, amongst the BTEM resolved spectra were five new bands that were not previously observed using conventional visual identification methods adopted by surface chemists. These new bands engendered new understanding to the mechanism of CO chemisorption on Ni(111). The combination of BTEM with residual spectral analysis was thus demonstrated to be efficacious for curve resolution of in situ RAIRS data obtained from surface chemistry studies.
Keywords: Self-modeling curve resolution; Chemometrics; Band-target entropy minimization, BTEM; Reflection–absorption infrared spectroscopy; In situ spectroscopy; Surface chemistry
Application of band-target entropy minimization (BTEM) and residual spectral analysis to in situ reflection–absorption infrared spectroscopy (RAIRS) data from surface chemistry studies by Boon Hong Kee; Wee-Sun Sim; Wee Chew (pp. 113-120).
The band-target entropy minimization (BTEM) curve resolution technique has been used to analyze in situ reflection–absorption infrared spectroscopy (RAIRS) data of CO chemisorption on Ni(111) single crystal surfaces. The bilinearity assumption for pRAIRS data, that is, negative logarithm to the base 10 of raw reflectance RAIRS data, was found to be sufficiently valid for the test data. A total of 11 real pure component pRAIRS spectra were elucidated via BTEM in tandem with an iterative residual spectral data analysis. Furthermore, 2 abstract pure component right singular vectors were found to account for all the pRAIRS non-linearities, baseline drifts and other spectral noise. In total, 100.2% of the pRAIRS signals were accounted for by these 13 spectral components. The 11 real pure component pRAIRS spectra and their corresponding relative concentration kinetic sequences correlate with 6 well-known adsorbed CO domain structures. Moreover, amongst the BTEM resolved spectra were five new bands that were not previously observed using conventional visual identification methods adopted by surface chemists. These new bands engendered new understanding to the mechanism of CO chemisorption on Ni(111). The combination of BTEM with residual spectral analysis was thus demonstrated to be efficacious for curve resolution of in situ RAIRS data obtained from surface chemistry studies.
Keywords: Self-modeling curve resolution; Chemometrics; Band-target entropy minimization, BTEM; Reflection–absorption infrared spectroscopy; In situ spectroscopy; Surface chemistry
Investigation of degradation mechanisms by portable Raman spectroscopy and thermodynamic speciation: The wall painting of Santa María de Lemoniz (Basque Country, North of Spain) by Maite Pérez-Alonso; Kepa Castro; Juan Manuel Madariaga (pp. 121-128).
This article presents the “in situ? and totally non destructive investigation of a wall painting in Santa María de Lemoniz (Biscay, Basque Country, Spain) by Raman microprobe spectroscopy 14 years after its restoration. Although no sample was allowed to be taken, it has been possible to determine the original pigments in the artwork (vermilion, red iron oxide, yellow iron oxide, carbon black, lead white), as well as some degradation products (calcium oxalate dihydrate, anhydrite). For the first time, the mechanism for the transformation of malachite into copper basic sulphates has been ascertained by the integration of Raman data with thermodynamic speciation studies. Moreover, some remarks regarding the unsuitability of the past intervention procedure with regard to the chemical stability of the artwork are made.
Keywords: Portable Raman spectroscopy; Wall painting; Pigment/mortar identification; Pigment/mortar degradation; Thermodynamic speciation
Investigation of degradation mechanisms by portable Raman spectroscopy and thermodynamic speciation: The wall painting of Santa María de Lemoniz (Basque Country, North of Spain) by Maite Pérez-Alonso; Kepa Castro; Juan Manuel Madariaga (pp. 121-128).
This article presents the “in situ” and totally non destructive investigation of a wall painting in Santa María de Lemoniz (Biscay, Basque Country, Spain) by Raman microprobe spectroscopy 14 years after its restoration. Although no sample was allowed to be taken, it has been possible to determine the original pigments in the artwork (vermilion, red iron oxide, yellow iron oxide, carbon black, lead white), as well as some degradation products (calcium oxalate dihydrate, anhydrite). For the first time, the mechanism for the transformation of malachite into copper basic sulphates has been ascertained by the integration of Raman data with thermodynamic speciation studies. Moreover, some remarks regarding the unsuitability of the past intervention procedure with regard to the chemical stability of the artwork are made.
Keywords: Portable Raman spectroscopy; Wall painting; Pigment/mortar identification; Pigment/mortar degradation; Thermodynamic speciation
Chromium speciation using sequential injection analysis and multivariate curve resolution by V. Gómez; M.S. Larrechi; M.P. Callao (pp. 129-135).
In this paper we develop a suitable method for the speciation of chromium in tanning and environmental water samples.We use sequential injection analysis (SIA) with a diode array detector linked to chemometric tools such as multivariate curve resolution-alternating least squares (MCR-ALS) to determine Cr(III) and Cr(VI) species. Although Cr(III) is an absorbent species, its sensitivity is much lower than that of Cr(VI). To increase its sensitivity, therefore, it was complexed with EDTA.This method involves generating a pH gradient in the system reactor that converts dichromate into chromate in such a way that, when the sample reaches the detector, selective areas are observed and a data matrix is obtained. Applying MCR enables Cr(III) and Cr(VI) to be successfully determined simultaneously in tanning and environmental wastewater samples.
Keywords: Chromium speciation; Sequential injection analysis; Multivariate curve resolution; Tanning and environmental samples
Chromium speciation using sequential injection analysis and multivariate curve resolution by V. Gómez; M.S. Larrechi; M.P. Callao (pp. 129-135).
In this paper we develop a suitable method for the speciation of chromium in tanning and environmental water samples.We use sequential injection analysis (SIA) with a diode array detector linked to chemometric tools such as multivariate curve resolution-alternating least squares (MCR-ALS) to determine Cr(III) and Cr(VI) species. Although Cr(III) is an absorbent species, its sensitivity is much lower than that of Cr(VI). To increase its sensitivity, therefore, it was complexed with EDTA.This method involves generating a pH gradient in the system reactor that converts dichromate into chromate in such a way that, when the sample reaches the detector, selective areas are observed and a data matrix is obtained. Applying MCR enables Cr(III) and Cr(VI) to be successfully determined simultaneously in tanning and environmental wastewater samples.
Keywords: Chromium speciation; Sequential injection analysis; Multivariate curve resolution; Tanning and environmental samples
Evaluation of a tungsten coil atomization-laser-induced fluorescence detection approach for trace elemental analysis by Muhsin Ezer; Seth A. Elwood; Bradley T. Jones; Josef B. Simeonsson (pp. 136-141).
The analytical utility of a tungsten (W)-coil atomization-laser-induced fluorescence (LIF) approach has been evaluated for trace level measurements of elemental chromium (Cr), arsenic (As), selenium (Se), antimony (Sb), lead (Pb), tin (Sn), copper (Cu), thallium (Tl), indium (In), cadmium (Cd), zinc (Zn) and mercury (Hg). Measurements of As, Cr, In, Se, Sb, Pb, Tl, and Sn were performed by laser-induced fluorescence using a single dye laser operating near 460nm whose output was converted by frequency doubling and stimulated Raman scattering to wavelengths ranging from 196 to 286nm for atomic excitation. Absolute limits of detection (LODs) of 1, 0.3, 0.3, 0.2, 1, 6, 1, 0.2 and 0.8pg and concentration LODs of 100, 30, 30, 20, 100, 600, 100, 20, and 80pg/mL were achieved for As, Se, Sb, Sn, In, Cu, Cr, Pb and Tl, respectively. Determinations of Hg, Pb, Zn and Cd were performed using two-color excitation approaches and resulted in absolute LODs of 2, 30, 5 and 0.6pg, respectively, and concentration LODs of 200, 3000, 500 and 60pg/mL, respectively. The sensitivities achieved by the W-coil LIF approaches compare well with those reported by W-coil atomic absorption spectrometry, graphite furnace atomic absorption spectrometry, and graphite furnace electrothermal atomization-LIF approaches. The accuracy of the approach was verified through the analysis of a multielement reference solution containing Sb, Pb and Tl which each had certified performance acceptance limits of 19.6–20.4μg/mL. The determined concentrations were 20.05±2.60, 20.70±2.27 and 20.60±2.46μg/mL, for Sb, Pb and Tl, respectively. The results demonstrate that W-coil LIF provides good analytical performance for trace analyses due to its high sensitivity, linearity, and capability to measure multiple elements using a single tunable laser and suggest that the development of portable W-coil LIF instrumentation using compact, solid-state lasers is feasible.
Keywords: Tungsten coil atomizer; Laser-induced fluorescence; Stimulated Raman scattering
Evaluation of a tungsten coil atomization-laser-induced fluorescence detection approach for trace elemental analysis by Muhsin Ezer; Seth A. Elwood; Bradley T. Jones; Josef B. Simeonsson (pp. 136-141).
The analytical utility of a tungsten (W)-coil atomization-laser-induced fluorescence (LIF) approach has been evaluated for trace level measurements of elemental chromium (Cr), arsenic (As), selenium (Se), antimony (Sb), lead (Pb), tin (Sn), copper (Cu), thallium (Tl), indium (In), cadmium (Cd), zinc (Zn) and mercury (Hg). Measurements of As, Cr, In, Se, Sb, Pb, Tl, and Sn were performed by laser-induced fluorescence using a single dye laser operating near 460nm whose output was converted by frequency doubling and stimulated Raman scattering to wavelengths ranging from 196 to 286nm for atomic excitation. Absolute limits of detection (LODs) of 1, 0.3, 0.3, 0.2, 1, 6, 1, 0.2 and 0.8pg and concentration LODs of 100, 30, 30, 20, 100, 600, 100, 20, and 80pg/mL were achieved for As, Se, Sb, Sn, In, Cu, Cr, Pb and Tl, respectively. Determinations of Hg, Pb, Zn and Cd were performed using two-color excitation approaches and resulted in absolute LODs of 2, 30, 5 and 0.6pg, respectively, and concentration LODs of 200, 3000, 500 and 60pg/mL, respectively. The sensitivities achieved by the W-coil LIF approaches compare well with those reported by W-coil atomic absorption spectrometry, graphite furnace atomic absorption spectrometry, and graphite furnace electrothermal atomization-LIF approaches. The accuracy of the approach was verified through the analysis of a multielement reference solution containing Sb, Pb and Tl which each had certified performance acceptance limits of 19.6–20.4μg/mL. The determined concentrations were 20.05±2.60, 20.70±2.27 and 20.60±2.46μg/mL, for Sb, Pb and Tl, respectively. The results demonstrate that W-coil LIF provides good analytical performance for trace analyses due to its high sensitivity, linearity, and capability to measure multiple elements using a single tunable laser and suggest that the development of portable W-coil LIF instrumentation using compact, solid-state lasers is feasible.
Keywords: Tungsten coil atomizer; Laser-induced fluorescence; Stimulated Raman scattering
Solid sampling-graphite furnace atomic absorption spectrometry for the direct determination of silver at trace and ultratrace levels by M. Resano; M. Aramendía; E. García-Ruiz; C. Crespo; M.A. Belarra (pp. 142-149).
In this work, the possibilities of solid sampling-graphite furnace atomic absorption spectrometry for the direct determination of silver in solid samples of very different nature (a biological sample, a soil, an ore concentrate and a polymer) and showing substantial differences in their analyte content (from approximately, 40ngg−1 up to 350μgg−1) have been evaluated, the goal always being to develop fast methods, only relying on the use of aqueous standards for calibration.Different factors had to be taken into account in order to develop suitable procedures for all the samples under investigation. Among the most important ones, the following can be mentioned: (i) optimization of the temperature program in order to selectively atomize the analyte; (ii) the use of chemical modifiers (such as Pd or HNO3), depending on the sample characteristics; (iii) appropriate wavelength, argon flow and sample mass selection (depending on the analyte content); (iv) the use of 3-field mode Zeeman-effect background correction in order to further expand the linear range up to 1000ng of Ag, which was needed for analysis of the sample showing the highest Ag content (polypropylene).The procedures finally proposed show interesting features for the determination of silver in solid samples: the advantage of using aqueous standard solutions for calibration, a high sample throughput (approximately, 15min per sample), a low detection limit (2ngg−1), sufficient precision (R.S.D. values in the vicinity of 10%) and a reduced risk of analyte losses and contamination.
Keywords: Solid sampling; Graphite furnace atomic absorption spectrometry; Silver determination; 3-Field mode Zeeman-effect background correction
Solid sampling-graphite furnace atomic absorption spectrometry for the direct determination of silver at trace and ultratrace levels by M. Resano; M. Aramendía; E. García-Ruiz; C. Crespo; M.A. Belarra (pp. 142-149).
In this work, the possibilities of solid sampling-graphite furnace atomic absorption spectrometry for the direct determination of silver in solid samples of very different nature (a biological sample, a soil, an ore concentrate and a polymer) and showing substantial differences in their analyte content (from approximately, 40ngg−1 up to 350μgg−1) have been evaluated, the goal always being to develop fast methods, only relying on the use of aqueous standards for calibration.Different factors had to be taken into account in order to develop suitable procedures for all the samples under investigation. Among the most important ones, the following can be mentioned: (i) optimization of the temperature program in order to selectively atomize the analyte; (ii) the use of chemical modifiers (such as Pd or HNO3), depending on the sample characteristics; (iii) appropriate wavelength, argon flow and sample mass selection (depending on the analyte content); (iv) the use of 3-field mode Zeeman-effect background correction in order to further expand the linear range up to 1000ng of Ag, which was needed for analysis of the sample showing the highest Ag content (polypropylene).The procedures finally proposed show interesting features for the determination of silver in solid samples: the advantage of using aqueous standard solutions for calibration, a high sample throughput (approximately, 15min per sample), a low detection limit (2ngg−1), sufficient precision (R.S.D. values in the vicinity of 10%) and a reduced risk of analyte losses and contamination.
Keywords: Solid sampling; Graphite furnace atomic absorption spectrometry; Silver determination; 3-Field mode Zeeman-effect background correction
Improved sensitivity for transition metal ions by use of sulfide in the Belousov–Zhabotinskii oscillating reaction by Jinzhang Gao; Hua Chen; Hongxia Dai; Dongyu Lv; Jie Ren; Lei Wang; Wu Yang (pp. 150-155).
A highly sensitive method for the determination of trace amounts of transition metal ions by use of sulfide in the Belousov–Zhabotinskii (B–Z) oscillating chemical reaction is proposed. The use of sulfide increased strongly the sensitivity of the B–Z reaction for transition metal ions, such as Ag+, Pb2+, Hg2+, Cd2+, Cu2+,and Bi3+. Results showed that the variational ratio of oscillating period ( PR) is linearly proportional to the negative logarithm of concentration of metal ions. The detection limit is down to 10−12molL−1. Various influencing factors on the determination were also examined.
Keywords: Belousov–Zhabotinskii (B–Z) oscillating chemical system; Trace analysis; Determination of cations; Transition metal ions
Improved sensitivity for transition metal ions by use of sulfide in the Belousov–Zhabotinskii oscillating reaction by Jinzhang Gao; Hua Chen; Hongxia Dai; Dongyu Lv; Jie Ren; Lei Wang; Wu Yang (pp. 150-155).
A highly sensitive method for the determination of trace amounts of transition metal ions by use of sulfide in the Belousov–Zhabotinskii (B–Z) oscillating chemical reaction is proposed. The use of sulfide increased strongly the sensitivity of the B–Z reaction for transition metal ions, such as Ag+, Pb2+, Hg2+, Cd2+, Cu2+,and Bi3+. Results showed that the variational ratio of oscillating period ( PR) is linearly proportional to the negative logarithm of concentration of metal ions. The detection limit is down to 10−12molL−1. Various influencing factors on the determination were also examined.
Keywords: Belousov–Zhabotinskii (B–Z) oscillating chemical system; Trace analysis; Determination of cations; Transition metal ions