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Analytica Chimica Acta (v.571, #2)
The potential of mid infrared spectroscopy (MIRS) for real time bioprocess monitoring by Payal Roychoudhury; Linda M. Harvey; Brian McNeil (pp. 159-166).
The need for effective bioprocess (fermentation) monitoring is growing in importance due to the rapid pace of change in the fermentation industry, and attendant financial pressures. Vibrational spectroscopy has shown great promise in bioprocess monitoring. In particular, recently attention has been focused on the capability of mid infrared spectroscopy (MIRS) to monitor multiple analytes in highly complex fermentation fluids. The potential of this powerful analytical technique is critically evaluated by discussion of relevant studies. The advantages and limitations of MIR are discussed in the context of “rival? technologies, such as near infrared, focusing especially on employing such techniques in bioprocesses for real time (either in situ or ex situ) measurements. The potential barriers to the development of MIRS for real time monitoring are identified and further research directions highlighted.
Keywords: Bioprocess monitoring; Fermentation; Mid infrared spectroscopy
The potential of mid infrared spectroscopy (MIRS) for real time bioprocess monitoring by Payal Roychoudhury; Linda M. Harvey; Brian McNeil (pp. 159-166).
The need for effective bioprocess (fermentation) monitoring is growing in importance due to the rapid pace of change in the fermentation industry, and attendant financial pressures. Vibrational spectroscopy has shown great promise in bioprocess monitoring. In particular, recently attention has been focused on the capability of mid infrared spectroscopy (MIRS) to monitor multiple analytes in highly complex fermentation fluids. The potential of this powerful analytical technique is critically evaluated by discussion of relevant studies. The advantages and limitations of MIR are discussed in the context of “rival” technologies, such as near infrared, focusing especially on employing such techniques in bioprocesses for real time (either in situ or ex situ) measurements. The potential barriers to the development of MIRS for real time monitoring are identified and further research directions highlighted.
Keywords: Bioprocess monitoring; Fermentation; Mid infrared spectroscopy
Combination of mid- and near-infrared spectroscopy for the determination of the quality properties of beers by Fernando A. Iñón; Salvador Garrigues; Miguel de la Guardia (pp. 167-174).
The combination of infrared (MIR) and near-infrared (NIR) spectroscopy has been employed for the determination of important quality parameters of beers, such as original and real extract and alcohol content. A population of 43 samples obtained from the Spanish market and including different types of beer, was evaluated. For each technique, spectra were obtained in triplicate. In the case of NIR a 1mm pathlength quartz flow cell was used, whereas attenuated total reflectance measurements were used in MIR. Cluster hierarchical analysis was employed to select calibration and validation data sets. The calibration set was composed of 15 samples, thus leaving 28 for validation. A critical evaluation of the prediction capability of multivariate methods established from the combination of NIR and MIR spectra was made. Partial least squares (PLS) and artificial neural networks (ANN) were evaluated for the treatment of data obtained in each individual technique and the combination of both. Different parameters of each methodology were optimized. A slightly better predictive performance was obtained for NIR–MIR combined spectra, and in all the cases ANN performs better than PLS, which may be interpreted from the existence of some non-linearity in the data. The root-mean-sqare-error of prediction (RMSEP) values obtained for the combined NIR–MIR spectra for the determination of real extract, original extract and ethanol were 0.076% w/w, 0.14% w/w and 0.091% v/v.
Keywords: Determination; Original and real extract; Alcohol content; Beers; Artificial neuronal networks; Partial least squares; Combination of spectroscopic techniques; Near-infrared; Middle-infrared; Attenuated total reflectance
Combination of mid- and near-infrared spectroscopy for the determination of the quality properties of beers by Fernando A. Iñón; Salvador Garrigues; Miguel de la Guardia (pp. 167-174).
The combination of infrared (MIR) and near-infrared (NIR) spectroscopy has been employed for the determination of important quality parameters of beers, such as original and real extract and alcohol content. A population of 43 samples obtained from the Spanish market and including different types of beer, was evaluated. For each technique, spectra were obtained in triplicate. In the case of NIR a 1mm pathlength quartz flow cell was used, whereas attenuated total reflectance measurements were used in MIR. Cluster hierarchical analysis was employed to select calibration and validation data sets. The calibration set was composed of 15 samples, thus leaving 28 for validation. A critical evaluation of the prediction capability of multivariate methods established from the combination of NIR and MIR spectra was made. Partial least squares (PLS) and artificial neural networks (ANN) were evaluated for the treatment of data obtained in each individual technique and the combination of both. Different parameters of each methodology were optimized. A slightly better predictive performance was obtained for NIR–MIR combined spectra, and in all the cases ANN performs better than PLS, which may be interpreted from the existence of some non-linearity in the data. The root-mean-sqare-error of prediction (RMSEP) values obtained for the combined NIR–MIR spectra for the determination of real extract, original extract and ethanol were 0.076% w/w, 0.14% w/w and 0.091% v/v.
Keywords: Determination; Original and real extract; Alcohol content; Beers; Artificial neuronal networks; Partial least squares; Combination of spectroscopic techniques; Near-infrared; Middle-infrared; Attenuated total reflectance
Fluorescent investigation of the interactions between N-( p-chlorophenyl)- N′-(1-naphthyl) thiourea and serum albumin: Synchronous fluorescence determination of serum albumin by Feng-Ling Cui; Jun-Li Wang; Yan-Rui Cui; Jian-Ping Li (pp. 175-183).
The interactions between N-( p-chlorophenyl)- N′-(1-naphthyl) thiourea and serum albumin were investigated by fluorescence spectroscopy and UV absorption spectrum under physiological conditions. The results of spectroscopic measurements suggested that N-( p-chlorophenyl)- N′-(1-naphthyl) thiourea should have a strong ability to quench the intrinsic fluorescence of both bovine serum albumin and human serum albumin through static quenching procedure, and the hydrophobic interaction was the predominant intermolecular force stabilizing the complex. Thermodynamic parameter enthalpy changes (Δ H) and entropy changes (Δ S) were calculated according to the Vant’Hoff equation. The binding distances between N-( p-chlorophenyl)- N′-(1-naphthyl) thiourea and the proteins were evaluated on the basis of the theory of Föster energy transfer. In addition, the effects of other ions on the binding constants of complexes were also discussed. Synchronous fluorescence technology was successfully applied to the determination of serum albumins added to the CPNT solution.
Keywords: N; -(; p; -chlorophenyl)-; N; ′-(1-naphthyl) thiourea (CPNT); Bovine serum albumin (BSA); Human serum albumin (HSA); Fluorescence spectroscopy; Synchronous fluorescence spectrum
Fluorescent investigation of the interactions between N-( p-chlorophenyl)- N′-(1-naphthyl) thiourea and serum albumin: Synchronous fluorescence determination of serum albumin by Feng-Ling Cui; Jun-Li Wang; Yan-Rui Cui; Jian-Ping Li (pp. 175-183).
The interactions between N-( p-chlorophenyl)- N′-(1-naphthyl) thiourea and serum albumin were investigated by fluorescence spectroscopy and UV absorption spectrum under physiological conditions. The results of spectroscopic measurements suggested that N-( p-chlorophenyl)- N′-(1-naphthyl) thiourea should have a strong ability to quench the intrinsic fluorescence of both bovine serum albumin and human serum albumin through static quenching procedure, and the hydrophobic interaction was the predominant intermolecular force stabilizing the complex. Thermodynamic parameter enthalpy changes (Δ H) and entropy changes (Δ S) were calculated according to the Vant’Hoff equation. The binding distances between N-( p-chlorophenyl)- N′-(1-naphthyl) thiourea and the proteins were evaluated on the basis of the theory of Föster energy transfer. In addition, the effects of other ions on the binding constants of complexes were also discussed. Synchronous fluorescence technology was successfully applied to the determination of serum albumins added to the CPNT solution.
Keywords: N; -(; p; -chlorophenyl)-; N; ′-(1-naphthyl) thiourea (CPNT); Bovine serum albumin (BSA); Human serum albumin (HSA); Fluorescence spectroscopy; Synchronous fluorescence spectrum
Flow injection analysis of ultratrace orthophosphate in seawater with solid-phase enrichment and luminol chemiluminescence detection by Ying Liang; Dongxing Yuan; Quanlong Li; Qingmei Lin (pp. 184-190).
Solid-phase extraction technique had been applied to extract molybdophosphoric heteropoly acid (MoP) paired with cetyltrimethylammonium bromide (CTAB) from seawater matrix using C18 sorbent. Chemiluminescence emission could be generated via MoP reaction with alkaline luminol. Based on these, a novel on-line solid-phase extraction method coupled with flow injection (FI) analysis and luminol chemiluminescence detection had been established to determine ultratrace orthophosphate in seawater. The MoP–CTAB compound could be efficiently extracted on an in-line Sep-Pak C18 cartridge, and rapidly eluted by 0.3moll−1 sulphuric acid–ethanol solution. Then the compound was reduced by luminol to produce chemiluminescence light, which could be detected using a luminescence analyzer. Experimental parameters were optimized using a univariate experimental design. Using artificial seawater with salinity of 35 as a matrix, the standard curve with a linear range between 0.005 and 0.194μmoll−1 had been obtained, and the recovery and the detection limit of the proposed method were found to be 92.5% and 0.002μmoll−1, respectively. The relative standard deviation (R.S.D.), which was determined over eight hour, was 4.66% ( n=7) for the artificial seawater at a concentration of 0.097μmoll−1 orthophosphate. Si of 200μmoll−1 would not interfere with the detection of 0.012μmoll−1 orthophosphate compound. Three typical seawater samples were analyzed using both the proposed method and the magnesium hydroxide-induced coprecipitation (MAGIC) method, and the results of the two methods showed no significant difference using the t test. Compared to the MAGIC method, the proposed method was more sensitive, time saving and easy for on-line analysis.
Keywords: Sep-Pak C18; On-line solid-phase extraction; Orthophosphate; Molybdophosphoric heteropoly acid; Cetyltrimethylammonium bromide; Luminol chemiluminescence
Flow injection analysis of ultratrace orthophosphate in seawater with solid-phase enrichment and luminol chemiluminescence detection by Ying Liang; Dongxing Yuan; Quanlong Li; Qingmei Lin (pp. 184-190).
Solid-phase extraction technique had been applied to extract molybdophosphoric heteropoly acid (MoP) paired with cetyltrimethylammonium bromide (CTAB) from seawater matrix using C18 sorbent. Chemiluminescence emission could be generated via MoP reaction with alkaline luminol. Based on these, a novel on-line solid-phase extraction method coupled with flow injection (FI) analysis and luminol chemiluminescence detection had been established to determine ultratrace orthophosphate in seawater. The MoP–CTAB compound could be efficiently extracted on an in-line Sep-Pak C18 cartridge, and rapidly eluted by 0.3moll−1 sulphuric acid–ethanol solution. Then the compound was reduced by luminol to produce chemiluminescence light, which could be detected using a luminescence analyzer. Experimental parameters were optimized using a univariate experimental design. Using artificial seawater with salinity of 35 as a matrix, the standard curve with a linear range between 0.005 and 0.194μmoll−1 had been obtained, and the recovery and the detection limit of the proposed method were found to be 92.5% and 0.002μmoll−1, respectively. The relative standard deviation (R.S.D.), which was determined over eight hour, was 4.66% ( n=7) for the artificial seawater at a concentration of 0.097μmoll−1 orthophosphate. Si of 200μmoll−1 would not interfere with the detection of 0.012μmoll−1 orthophosphate compound. Three typical seawater samples were analyzed using both the proposed method and the magnesium hydroxide-induced coprecipitation (MAGIC) method, and the results of the two methods showed no significant difference using the t test. Compared to the MAGIC method, the proposed method was more sensitive, time saving and easy for on-line analysis.
Keywords: Sep-Pak C18; On-line solid-phase extraction; Orthophosphate; Molybdophosphoric heteropoly acid; Cetyltrimethylammonium bromide; Luminol chemiluminescence
Gas chromatographic–mass spectrometric analysis of N-acetylated amino acids: The first case of aminoacylase I deficiency by Erik Gerlo; Rudy Van Coster; Willy Lissens; Gerda Winckelmans; Linda De Meirleir; Ron Wevers (pp. 191-199).
During the metabolic work-up of a patient presenting with neonatal convulsions, we consistently observed the presence of unusual peaks in the gas chromatographic–mass spectrometric analysis of urinary organic acids. The gas chromatographic–mass spectrometric characteristics of the unusual peaks suggested that they corresponded to derivatives of N-acetylated amino acids. The tentative identification was confirmed by the identity of retention times and mass spectra of the trimethylsilyl derivatives of the authentic compounds. We describe our observations that led to the identification of the various N-acetylated amino acids in this first patient with a confirmed deficiency of aminoacylase I, an enzyme involved in the cytosolic degradation of N-terminally modified proteins. The potential and limitations of urinary organic acid analysis for the detection of N-acetylated amino acids was further studied using pure compounds. In addition, we provide mass spectral data for 37 trimethylsilyl derivatives from 17 N-acetylated amino acids, most of which have not been reported previously. Our data provide valuable information that will help the clinical laboratorians who are responsible for organic acid analysis to recognize this new condition and could aid its detection in other patients.
Keywords: Aminoacylase I; Inborn error; Gas chromatographic–mass spectrometric; N; -Acetylated amino acids; Trimethylsilylation
Gas chromatographic–mass spectrometric analysis of N-acetylated amino acids: The first case of aminoacylase I deficiency by Erik Gerlo; Rudy Van Coster; Willy Lissens; Gerda Winckelmans; Linda De Meirleir; Ron Wevers (pp. 191-199).
During the metabolic work-up of a patient presenting with neonatal convulsions, we consistently observed the presence of unusual peaks in the gas chromatographic–mass spectrometric analysis of urinary organic acids. The gas chromatographic–mass spectrometric characteristics of the unusual peaks suggested that they corresponded to derivatives of N-acetylated amino acids. The tentative identification was confirmed by the identity of retention times and mass spectra of the trimethylsilyl derivatives of the authentic compounds. We describe our observations that led to the identification of the various N-acetylated amino acids in this first patient with a confirmed deficiency of aminoacylase I, an enzyme involved in the cytosolic degradation of N-terminally modified proteins. The potential and limitations of urinary organic acid analysis for the detection of N-acetylated amino acids was further studied using pure compounds. In addition, we provide mass spectral data for 37 trimethylsilyl derivatives from 17 N-acetylated amino acids, most of which have not been reported previously. Our data provide valuable information that will help the clinical laboratorians who are responsible for organic acid analysis to recognize this new condition and could aid its detection in other patients.
Keywords: Aminoacylase I; Inborn error; Gas chromatographic–mass spectrometric; N; -Acetylated amino acids; Trimethylsilylation
A new immune resonance scattering spectral assay for trace fibrinogen with gold nanoparticle label by Zhi-Liang Jiang; Shuang-Jiao Sun; Ai-Hui Liang; Chang-Jiu Liu (pp. 200-205).
Gold nanoparticles in size of 9.0nm was prepared by the trisodium citrate and used to label goat anti-human fibrinogen. In the pH 6.2 buffer solution and in the presence of polyethylene glycol (PEG), the immune reaction between gold-labeled goat anti-human fibrinogen and fibrinogen took place and the labeled gold nanoparticles were released from the goat anti-human fibrinogen, and the released gold particles aggregated which leaded the resonance scattering intensity at 560nm ( I560nm) to enhance greatly. The I560nm is proportional to the fibrinogen concentration in the range from 0.027 to 1.07μgmL−1. The detection limit is 1.14ngmL−1. This simple assay was applied to determination of fibrinogen in human plasma, with satisfactory results.
Keywords: Fibrinogen; Immune resonance scattering spectral assay; Gold nanoparticle label
A new immune resonance scattering spectral assay for trace fibrinogen with gold nanoparticle label by Zhi-Liang Jiang; Shuang-Jiao Sun; Ai-Hui Liang; Chang-Jiu Liu (pp. 200-205).
Gold nanoparticles in size of 9.0nm was prepared by the trisodium citrate and used to label goat anti-human fibrinogen. In the pH 6.2 buffer solution and in the presence of polyethylene glycol (PEG), the immune reaction between gold-labeled goat anti-human fibrinogen and fibrinogen took place and the labeled gold nanoparticles were released from the goat anti-human fibrinogen, and the released gold particles aggregated which leaded the resonance scattering intensity at 560nm ( I560nm) to enhance greatly. The I560nm is proportional to the fibrinogen concentration in the range from 0.027 to 1.07μgmL−1. The detection limit is 1.14ngmL−1. This simple assay was applied to determination of fibrinogen in human plasma, with satisfactory results.
Keywords: Fibrinogen; Immune resonance scattering spectral assay; Gold nanoparticle label
Size effect in thiol and amine binding to small Pt nanoparticles by J. Yang; Jim Yang Lee; Heng-Phon Too (pp. 206-210).
A study was carried out to compare the binding affinities of 1-dodecanethiol and dodecylamine for small Pt nanoparticles. The results showed that the affinity of thiol for Pt nanoparticles increases with increasing particle size whereas the affinity of amine for Pt nanoparticles decreases. The divergence in binding affinities has resulted in differences in catalytic activities of thiol- and amine-protected Pt nanoparticles in the room temperature electro-oxidation of methanol (a fuel cell reaction). It was therefore possible for the larger Pt nanoparticles to be catalytically more active than the smaller Pt nanoparticles up to a certain critical size, before the surface area effects of nanoparticles become noticeable.
Keywords: 1-Dodecanethiol; Dodecylamine; Pt nanoparticle; Binding affinity; Methanol oxidation
Size effect in thiol and amine binding to small Pt nanoparticles by J. Yang; Jim Yang Lee; Heng-Phon Too (pp. 206-210).
A study was carried out to compare the binding affinities of 1-dodecanethiol and dodecylamine for small Pt nanoparticles. The results showed that the affinity of thiol for Pt nanoparticles increases with increasing particle size whereas the affinity of amine for Pt nanoparticles decreases. The divergence in binding affinities has resulted in differences in catalytic activities of thiol- and amine-protected Pt nanoparticles in the room temperature electro-oxidation of methanol (a fuel cell reaction). It was therefore possible for the larger Pt nanoparticles to be catalytically more active than the smaller Pt nanoparticles up to a certain critical size, before the surface area effects of nanoparticles become noticeable.
Keywords: 1-Dodecanethiol; Dodecylamine; Pt nanoparticle; Binding affinity; Methanol oxidation
Attachment of nickel hexacyanoferrates nanoparticles on carbon nanotubes: Preparation, characterization and bioapplication by Minghui Yang; Yunhui Yang; Fengli Qu; Yashuang Lu; Guoli Shen; Ruqin Yu (pp. 211-217).
The successful attachment of nickel hexacyanoferrate nanoparticles to carbon nanotubes through a simple, two-step procedure is reported. Histidine can be covalently linked to the carbon nanotube surface, which can then be used as interlinker for the binding of nickel hexacyanoferrate nanoparticles. A detailed investigation by Fourier transform infrared spectra (FT-IR), transmission electron microscopy, UV–vis and electrochemistry was performed in order to elucidate the preparation process and properties of the nanocomposites. Abundant nanoparticles were found attached onto the carbon nanotube surface and the nanocomposites are highly stable. Additionally, the nanostructure exhibits more efficient electron transfer ability and larger electrochemical response towards hydrogen peroxide as compared to the nanoparticles and carbon nanotubes physically mixed together. With the immobilization of cholesterol oxidase onto the nanostructure modified electrode surface, a biosensor that responds sensitively to cholesterol has been constructed. In pH 6.98 phosphate buffer, an almost interference free determination of cholesterol has been observed at −0.2V versus SCE with a linear range from 0.005 to 3mM and response time <20s.
Keywords: Biosensor; Cholesterol oxidase; Electrochemistry; Histidine; Nanostructure
Attachment of nickel hexacyanoferrates nanoparticles on carbon nanotubes: Preparation, characterization and bioapplication by Minghui Yang; Yunhui Yang; Fengli Qu; Yashuang Lu; Guoli Shen; Ruqin Yu (pp. 211-217).
The successful attachment of nickel hexacyanoferrate nanoparticles to carbon nanotubes through a simple, two-step procedure is reported. Histidine can be covalently linked to the carbon nanotube surface, which can then be used as interlinker for the binding of nickel hexacyanoferrate nanoparticles. A detailed investigation by Fourier transform infrared spectra (FT-IR), transmission electron microscopy, UV–vis and electrochemistry was performed in order to elucidate the preparation process and properties of the nanocomposites. Abundant nanoparticles were found attached onto the carbon nanotube surface and the nanocomposites are highly stable. Additionally, the nanostructure exhibits more efficient electron transfer ability and larger electrochemical response towards hydrogen peroxide as compared to the nanoparticles and carbon nanotubes physically mixed together. With the immobilization of cholesterol oxidase onto the nanostructure modified electrode surface, a biosensor that responds sensitively to cholesterol has been constructed. In pH 6.98 phosphate buffer, an almost interference free determination of cholesterol has been observed at −0.2V versus SCE with a linear range from 0.005 to 3mM and response time <20s.
Keywords: Biosensor; Cholesterol oxidase; Electrochemistry; Histidine; Nanostructure
Electronic micropipettor: A versatile fluid propulsion and injection device for micro-flow analysis by Daniela Daniel; Ivano G.R. Gutz (pp. 218-227).
The shortage of ready to use small sized liquid propulsion and switching devices for microfluidic cells (μ-cell) is a bottleneck in the dissemination of micro-flow analysis (μ-FA), now that microfluidic electrochemical cells can be designed and assembled in any laboratory by thermal transfer of laser printed masks and CD-Rs. Microprocessor-controlled electronic pipettors, commercially available with minimum capacity of 10μL, represent a compromise solution between oversized peristaltic pumps and tiny “on a chip? micropumps and valves. The versatility of the electronic pipette coupled with the μ-cell (13-μm deep longitudinal channel) was demonstrated in three operation modes: SIA like, FIA like and direct injection analysis (DIA). Injections of 100nL K4Fe(CN)6 (0.1molL−1 KCl) define a linear analytical curve ( r=0.999) in the range of 5×10−7 to 1.0×10−3molL−1 for flow amperometry at a gold electrode potentiostated at 0.4V versus Ag/AgCl. Methods for the amperometric μ-flow determination of promethazine (FIA like), dipyrone (SIA like) and chlorpromazine (DIA) in pharmaceutical formulations were developed and applied to real samples. Excellent linearity of analytical curves and high repeatability (R.S.D.<3.0%) at the low picomole range was obtained and all results for real samples were in agreement with reference methods. The results reflect the stability and the reliability of the setups envisioned for the electronic pipette coupled with amperometric μ-cell and the validity of the μ-FA methods.
Keywords: Electronic pipette; Micro-flow analysis; Micro-flow injection analysis; Microfluidics; Microdevices; Gold electrode; Direct injection analysis; Flow amperometry; Dipyrone analysis; Promethazine analysis; Chlorpromazine analysis
Electronic micropipettor: A versatile fluid propulsion and injection device for micro-flow analysis by Daniela Daniel; Ivano G.R. Gutz (pp. 218-227).
The shortage of ready to use small sized liquid propulsion and switching devices for microfluidic cells (μ-cell) is a bottleneck in the dissemination of micro-flow analysis (μ-FA), now that microfluidic electrochemical cells can be designed and assembled in any laboratory by thermal transfer of laser printed masks and CD-Rs. Microprocessor-controlled electronic pipettors, commercially available with minimum capacity of 10μL, represent a compromise solution between oversized peristaltic pumps and tiny “on a chip” micropumps and valves. The versatility of the electronic pipette coupled with the μ-cell (13-μm deep longitudinal channel) was demonstrated in three operation modes: SIA like, FIA like and direct injection analysis (DIA). Injections of 100nL K4Fe(CN)6 (0.1molL−1 KCl) define a linear analytical curve ( r=0.999) in the range of 5×10−7 to 1.0×10−3molL−1 for flow amperometry at a gold electrode potentiostated at 0.4V versus Ag/AgCl. Methods for the amperometric μ-flow determination of promethazine (FIA like), dipyrone (SIA like) and chlorpromazine (DIA) in pharmaceutical formulations were developed and applied to real samples. Excellent linearity of analytical curves and high repeatability (R.S.D.<3.0%) at the low picomole range was obtained and all results for real samples were in agreement with reference methods. The results reflect the stability and the reliability of the setups envisioned for the electronic pipette coupled with amperometric μ-cell and the validity of the μ-FA methods.
Keywords: Electronic pipette; Micro-flow analysis; Micro-flow injection analysis; Microfluidics; Microdevices; Gold electrode; Direct injection analysis; Flow amperometry; Dipyrone analysis; Promethazine analysis; Chlorpromazine analysis
On-chip integrated hydrolysis, fluorescent labeling, and electrophoretic separation utilized for acetylcholinesterase assay by Vered Heleg-Shabtai; Natzach Gratziany; Zvi Liron (pp. 228-234).
A sensitive on-chip acetylcholinesterase (AChE) assay that serves as a basis for the development of a fully integrated on-chip AChE-inhibitor detection assay is presented. The sequential steps required for the on-chip analysis process were integrated into a microchip. Transport and mixing of the reagents occurred by a combination of electroosmosis and electrophoresis using computer-controlled electrokinetic transport. AChE-catalyzed hydrolysis of acetylthiocholine to thiocholine was determined by on-chip reaction of thiocholine with eosinmaleimide, and the resulting thioether was electrophoretically separated and detected by laser-induced fluorescence (LIF). Enzyme-substrate mixing and reaction by confluent flow of reagents was compared with electrophoretically mediated microanalysis (EMMA), based on injection of an enzyme plug, and the utilization of differences in electrophoretic mobility as a driving force for efficient mixing and reaction. Both methods yielded similar results, however the EMMA-plug technique is preferable. The EMMA-plug technique was optimized for length and pushing time of enzyme plug, length of dyes mixture plug, acetylthiocholine concentration, and detector location. Detection of O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothiolate (VX) and paraoxon, two AChE inhibitors, was demonstrated by off-chip mixing of the inhibitor and AChE, followed by the on-chip AChE assay. Limit of detection of VX for 5.5min incubation and of paraoxon for 8min incubation was 4×10−10 and 4×10−7M, respectively. Utilization of the AChE microchip assay for inhibition kinetics was demonstrated also by evaluation of the inhibitor-enzyme bimolecular reaction constant ( k i). The evaluated k i values for VX and paraoxon for AChE from the electric eel were 3.5×107 and 1.7×105M−1min−1, respectively, conforming well to reported values obtained by bulk methods.
Keywords: Acetylcholinesterase; Electrophoretic separation; Laser-induced fluorescence; Microchip; Paraoxon; O; -Ethyl; S; -[2-(diisopropylamino)ethyl] methylphosphonothiolate
On-chip integrated hydrolysis, fluorescent labeling, and electrophoretic separation utilized for acetylcholinesterase assay by Vered Heleg-Shabtai; Natzach Gratziany; Zvi Liron (pp. 228-234).
A sensitive on-chip acetylcholinesterase (AChE) assay that serves as a basis for the development of a fully integrated on-chip AChE-inhibitor detection assay is presented. The sequential steps required for the on-chip analysis process were integrated into a microchip. Transport and mixing of the reagents occurred by a combination of electroosmosis and electrophoresis using computer-controlled electrokinetic transport. AChE-catalyzed hydrolysis of acetylthiocholine to thiocholine was determined by on-chip reaction of thiocholine with eosinmaleimide, and the resulting thioether was electrophoretically separated and detected by laser-induced fluorescence (LIF). Enzyme-substrate mixing and reaction by confluent flow of reagents was compared with electrophoretically mediated microanalysis (EMMA), based on injection of an enzyme plug, and the utilization of differences in electrophoretic mobility as a driving force for efficient mixing and reaction. Both methods yielded similar results, however the EMMA-plug technique is preferable. The EMMA-plug technique was optimized for length and pushing time of enzyme plug, length of dyes mixture plug, acetylthiocholine concentration, and detector location. Detection of O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothiolate (VX) and paraoxon, two AChE inhibitors, was demonstrated by off-chip mixing of the inhibitor and AChE, followed by the on-chip AChE assay. Limit of detection of VX for 5.5min incubation and of paraoxon for 8min incubation was 4×10−10 and 4×10−7M, respectively. Utilization of the AChE microchip assay for inhibition kinetics was demonstrated also by evaluation of the inhibitor-enzyme bimolecular reaction constant ( k i). The evaluated k i values for VX and paraoxon for AChE from the electric eel were 3.5×107 and 1.7×105M−1min−1, respectively, conforming well to reported values obtained by bulk methods.
Keywords: Acetylcholinesterase; Electrophoretic separation; Laser-induced fluorescence; Microchip; Paraoxon; O; -Ethyl; S; -[2-(diisopropylamino)ethyl] methylphosphonothiolate
Monolithic molecularly imprinted polymer for sulfamethoxazole and molecular recognition properties in aqueous mobile phase by Xiangjun Liu; Canbin Ouyang; Rui Zhao; Dihua Shangguan; Yi Chen; Guoquan Liu (pp. 235-241).
A monolithic molecularly imprinted polymer (monolithic MIP) for sulfamethoxazole (SMO) was prepared by in situ polymerization method as the HPLC stationary phase. By optimizing the polymerization conditions, the monolithic MIP showed highly specific recognition for the template SMO over its three structurally related analogs. As shown by SEM and the pore size distribution profile, the resultant MIP monolith showed a main pore diameter of 594nm and a large specific surface area of 124m2g−1, this allowed the mobile phase to flow through the column with low backpressure. Furthermore, the recognition abilities of the monolithic MIP in aqueous and organic media were studied. The results exhibited that the monolithic MIP possessed excellent recognition ability in aqueous media. Hydrophobic interactions, in addition to shape recognition, were the dominant effect for recognition in the mobile phase with high water content. Moreover, the binding sites and the dissociation constant were also determined by frontal chromatography as 122μmolg−1 and 1.88×10−5molL−1, respectively, which demonstrated that the obtained SMO-MIP monolith had a high binding capacity and strong affinity ability to the template molecule. Furthermore, the resultant SMO-MIP monolith was used as HPLC column directly to determine the SMO contents in three kinds of pharmaceutical tablets with the optimized aqueous mobile phase.
Keywords: Molecularly imprinted polymer; Monolithic; Aqueous phase recognition; Sulfamethoxazole; Pharmaceutical analysis
Monolithic molecularly imprinted polymer for sulfamethoxazole and molecular recognition properties in aqueous mobile phase by Xiangjun Liu; Canbin Ouyang; Rui Zhao; Dihua Shangguan; Yi Chen; Guoquan Liu (pp. 235-241).
A monolithic molecularly imprinted polymer (monolithic MIP) for sulfamethoxazole (SMO) was prepared by in situ polymerization method as the HPLC stationary phase. By optimizing the polymerization conditions, the monolithic MIP showed highly specific recognition for the template SMO over its three structurally related analogs. As shown by SEM and the pore size distribution profile, the resultant MIP monolith showed a main pore diameter of 594nm and a large specific surface area of 124m2g−1, this allowed the mobile phase to flow through the column with low backpressure. Furthermore, the recognition abilities of the monolithic MIP in aqueous and organic media were studied. The results exhibited that the monolithic MIP possessed excellent recognition ability in aqueous media. Hydrophobic interactions, in addition to shape recognition, were the dominant effect for recognition in the mobile phase with high water content. Moreover, the binding sites and the dissociation constant were also determined by frontal chromatography as 122μmolg−1 and 1.88×10−5molL−1, respectively, which demonstrated that the obtained SMO-MIP monolith had a high binding capacity and strong affinity ability to the template molecule. Furthermore, the resultant SMO-MIP monolith was used as HPLC column directly to determine the SMO contents in three kinds of pharmaceutical tablets with the optimized aqueous mobile phase.
Keywords: Molecularly imprinted polymer; Monolithic; Aqueous phase recognition; Sulfamethoxazole; Pharmaceutical analysis
A surface-fluorinated-TiO2–KMnO4 photocatalytic system for determination of chemical oxygen demand by Lihua Zhu; Yu’e Chen; Yinghui Wu; Xiurong Li; Heqing Tang (pp. 242-247).
A new method for chemical oxygen demand (COD) determination has been developed, based on photocatalytic oxidative degradation by using a fluorinated-TiO2–KMnO4 system. In such a system, a linear correlation is observed between the amount of oxidizable dissolved organic matter and the amount of MnO4− consumed by the coupled reduction process. Thus, the COD determination is transformed to a simple and direct determination of the deletion of MnO4−. The surface fluorination of TiO2 nanoparticles can enhance the rate of photocatalytic oxidation of organic matter and the rate of coupled photocatalytic reduction of MnO4−. This makes the method be rapid, environment friendly and easy for operation. Under optimized conditions, this method can respond linearly to COD of potassium hydrogen phthalate (KHP) in the range of 0.1–280mgL−1, with a detection limit of 0.02mgL−1 COD. The COD in samples of tap water, lake water and paper industry sewage has been determined satisfactorily by using this method.
Keywords: Chemical oxygen demand; Titania; Photocatalysis; Fluoride; Permanganate
A surface-fluorinated-TiO2–KMnO4 photocatalytic system for determination of chemical oxygen demand by Lihua Zhu; Yu’e Chen; Yinghui Wu; Xiurong Li; Heqing Tang (pp. 242-247).
A new method for chemical oxygen demand (COD) determination has been developed, based on photocatalytic oxidative degradation by using a fluorinated-TiO2–KMnO4 system. In such a system, a linear correlation is observed between the amount of oxidizable dissolved organic matter and the amount of MnO4− consumed by the coupled reduction process. Thus, the COD determination is transformed to a simple and direct determination of the deletion of MnO4−. The surface fluorination of TiO2 nanoparticles can enhance the rate of photocatalytic oxidation of organic matter and the rate of coupled photocatalytic reduction of MnO4−. This makes the method be rapid, environment friendly and easy for operation. Under optimized conditions, this method can respond linearly to COD of potassium hydrogen phthalate (KHP) in the range of 0.1–280mgL−1, with a detection limit of 0.02mgL−1 COD. The COD in samples of tap water, lake water and paper industry sewage has been determined satisfactorily by using this method.
Keywords: Chemical oxygen demand; Titania; Photocatalysis; Fluoride; Permanganate
Multi-way modeling of hydro-chemical data of an alluvial river system—A case study by Kunwar P. Singh; Amrita Malik; Vinod K. Singh; Nikita Basant; Sarita Sinha (pp. 248-259).
A large data set pertaining to water quality of an alluvial river was analyzed using multi-way data analysis methods with a view to extract the hidden information, spatial and temporal variation trends in the river water quality. Four-way data (8 monitoring sites×22 water quality variables×10 monitoring years×12 sampling months) analysis was performed using PARAFAC and Tucker3 models. A two component PARAFAC model, although explained 35.1% of the data variance, could not fit to the data set. Tucker3 model of optimum complexity (2,3,1,3) explaining 39.7% of the data variance, allowed interpretation of the data information in four modes. The model explained spatial and temporal variation trends in terms of water quality variables during the study period and revealed that sampling sites in mid-stretch of the river were dominated mainly by the variables of anthropogenic origin. The results delineated the mid stretch of the river as critical from pollution point of view and also identified summer months as having high influence on river water quality in this stretch. The information regarding spatial and temporal variations in water quality generated by the four-way modeling of data would be useful in developing long-term water resources management strategies in the river basin.
Keywords: Multi-way modeling; PARAFAC; Tucker3; Multi-way partial least squares; Water quality; Residual analysis
Multi-way modeling of hydro-chemical data of an alluvial river system—A case study by Kunwar P. Singh; Amrita Malik; Vinod K. Singh; Nikita Basant; Sarita Sinha (pp. 248-259).
A large data set pertaining to water quality of an alluvial river was analyzed using multi-way data analysis methods with a view to extract the hidden information, spatial and temporal variation trends in the river water quality. Four-way data (8 monitoring sites×22 water quality variables×10 monitoring years×12 sampling months) analysis was performed using PARAFAC and Tucker3 models. A two component PARAFAC model, although explained 35.1% of the data variance, could not fit to the data set. Tucker3 model of optimum complexity (2,3,1,3) explaining 39.7% of the data variance, allowed interpretation of the data information in four modes. The model explained spatial and temporal variation trends in terms of water quality variables during the study period and revealed that sampling sites in mid-stretch of the river were dominated mainly by the variables of anthropogenic origin. The results delineated the mid stretch of the river as critical from pollution point of view and also identified summer months as having high influence on river water quality in this stretch. The information regarding spatial and temporal variations in water quality generated by the four-way modeling of data would be useful in developing long-term water resources management strategies in the river basin.
Keywords: Multi-way modeling; PARAFAC; Tucker3; Multi-way partial least squares; Water quality; Residual analysis
Chemical speciation of Co, Ni, Cu, and Zn in mine effluents and effects of dilution of the effluent on release of the above metals from their metal–dissolved organic carbon (DOC) complexes by Parthasarathi Chakraborty; Chuni L. Chakrabarti (pp. 260-269).
The paper explores the lability of DOC complexes of Co, Ni, Cu, and Zn in the mining effluent, and investigates the effects of dilution of the effluent on the release of metals from the metal–DOC complexes. This study was done using competing ligand exchange method in conjunction with adsorptive cathodic stripping voltammetry on effluent samples from Copper Cliff Mine, Sudbury, Canada, using two samples of the effluent: one, undiluted (100%) effluent, and the other, diluted (45%) effluent. The dilution was done with tap water in order to determine the effects of dilution on the metal complexes in the effluents when they were discharged into receiving streams of freshwaters. The dilution of the effluent had a small effect on release of Cu from the Cu–DOC complexes, but had a much greater effect on the release of Zn from the Zn–DOC complexes. The release of Ni and Co from their DOC complexes decreased drastically on dilution of the effluent. The much greater release of Cu from the Cu–DOC complexes compared to the release of Ni, Co, and Zn from their DOC complexes in both the undiluted and the diluted effluent was probably due to the higher absolute concentration of Cu and the higher [Cu]/[DOC] ratio. The drastic decrease in the release of Ni and Co from the Ni– and Co–DOC complexes in the diluted (45%) effluent compared with the undiluted (100%) effluent probably resulted from strengthening of the metal–DOC bond due to the reduced screening of charges by a smaller concentration of Ca2+ in the diluted (45%) effluent. This work also shows that change in the ionic strength produces conformational changes in and in aggregation and precipitation of the DOC and also changes in electrostatic interactions between the metal cations and the humate polyanions.
Keywords: Mine effluents; Competing ligand exchange method; Adsorptive cathodic stripping voltammetry; Metal–DOC bond; Ligand field stabilization energy
Chemical speciation of Co, Ni, Cu, and Zn in mine effluents and effects of dilution of the effluent on release of the above metals from their metal–dissolved organic carbon (DOC) complexes by Parthasarathi Chakraborty; Chuni L. Chakrabarti (pp. 260-269).
The paper explores the lability of DOC complexes of Co, Ni, Cu, and Zn in the mining effluent, and investigates the effects of dilution of the effluent on the release of metals from the metal–DOC complexes. This study was done using competing ligand exchange method in conjunction with adsorptive cathodic stripping voltammetry on effluent samples from Copper Cliff Mine, Sudbury, Canada, using two samples of the effluent: one, undiluted (100%) effluent, and the other, diluted (45%) effluent. The dilution was done with tap water in order to determine the effects of dilution on the metal complexes in the effluents when they were discharged into receiving streams of freshwaters. The dilution of the effluent had a small effect on release of Cu from the Cu–DOC complexes, but had a much greater effect on the release of Zn from the Zn–DOC complexes. The release of Ni and Co from their DOC complexes decreased drastically on dilution of the effluent. The much greater release of Cu from the Cu–DOC complexes compared to the release of Ni, Co, and Zn from their DOC complexes in both the undiluted and the diluted effluent was probably due to the higher absolute concentration of Cu and the higher [Cu]/[DOC] ratio. The drastic decrease in the release of Ni and Co from the Ni– and Co–DOC complexes in the diluted (45%) effluent compared with the undiluted (100%) effluent probably resulted from strengthening of the metal–DOC bond due to the reduced screening of charges by a smaller concentration of Ca2+ in the diluted (45%) effluent. This work also shows that change in the ionic strength produces conformational changes in and in aggregation and precipitation of the DOC and also changes in electrostatic interactions between the metal cations and the humate polyanions.
Keywords: Mine effluents; Competing ligand exchange method; Adsorptive cathodic stripping voltammetry; Metal–DOC bond; Ligand field stabilization energy
Analysis of heavy metals in road-deposited sediments by Lars Herngren; Ashantha Goonetilleke; Godwin A. Ayoko (pp. 270-278).
Road-deposited sediments were analysed for heavy metal concentrations at three different landuses (residential, industrial, commercial) in Queensland State, Australia. The sediments were collected using a domestic vacuum cleaner which was proven to be highly efficient in collecting sub-micron particles. Five particle sizes were analysed separately for eight heavy metal elements (Zn, Fe, Pb, Cd, Cu, Cr, Al and Mn). At all sites, the maximum concentration of the heavy metals occurred in the 0.45–75μm particle size range, which conventional street cleaning services do not remove efficiently. Multicriteria decision making methods (MCDM), PROMETHEE and GAIA, were employed in the data analysis. PROMETHEE, a non-parametric ranking analysis procedure, was used to rank the metal contents of the sediments sampled at each site. The most polluted site and particle size range were the industrial site and the 0.45–75μm range, respectively. Although the industrial site displayed the highest metal concentrations, the highest heavy metal loading coincided with the highest sediment load, which occurred at the commercial site. GAIA, a special form of principal component analysis, was applied to determine correlations between the heavy metals and particle size ranges and also to assess possible correlation with total organic carbon (TOC). The GAIA-planes revealed that irrespective of the site, most of the heavy metals are adsorbed to sediments below 150μm. A weak correlation was found between Zn, Mn and TOC at the commercial site. This could lead to higher bioavailability of these metals through complexation reactions with the organic species in the sediments.
Keywords: Heavy metals; Preference ranking organization method for enrichment evaluation and graphical analysis for interactive assistance; Urban water quality; Chemometrics; Multicriteria decision making methods
Analysis of heavy metals in road-deposited sediments by Lars Herngren; Ashantha Goonetilleke; Godwin A. Ayoko (pp. 270-278).
Road-deposited sediments were analysed for heavy metal concentrations at three different landuses (residential, industrial, commercial) in Queensland State, Australia. The sediments were collected using a domestic vacuum cleaner which was proven to be highly efficient in collecting sub-micron particles. Five particle sizes were analysed separately for eight heavy metal elements (Zn, Fe, Pb, Cd, Cu, Cr, Al and Mn). At all sites, the maximum concentration of the heavy metals occurred in the 0.45–75μm particle size range, which conventional street cleaning services do not remove efficiently. Multicriteria decision making methods (MCDM), PROMETHEE and GAIA, were employed in the data analysis. PROMETHEE, a non-parametric ranking analysis procedure, was used to rank the metal contents of the sediments sampled at each site. The most polluted site and particle size range were the industrial site and the 0.45–75μm range, respectively. Although the industrial site displayed the highest metal concentrations, the highest heavy metal loading coincided with the highest sediment load, which occurred at the commercial site. GAIA, a special form of principal component analysis, was applied to determine correlations between the heavy metals and particle size ranges and also to assess possible correlation with total organic carbon (TOC). The GAIA-planes revealed that irrespective of the site, most of the heavy metals are adsorbed to sediments below 150μm. A weak correlation was found between Zn, Mn and TOC at the commercial site. This could lead to higher bioavailability of these metals through complexation reactions with the organic species in the sediments.
Keywords: Heavy metals; Preference ranking organization method for enrichment evaluation and graphical analysis for interactive assistance; Urban water quality; Chemometrics; Multicriteria decision making methods
Isotope dilution–thermal ionisation mass spectrometric analysis for tin in a fly ash material by Carolina Hernández; Marta Fernández; Alberto J. Quejido; Dolores M. Sánchez; Ramón Morante; Raúl Martín (pp. 279-287).
Isotope dilution–thermal ionisation mass spectrometry (ID–TIMS) analysis has been applied to the determination of tin in a fly ash sample supplied by the EC Joint Research Centre (Ispra, Italy). The proposed procedure includes the silica gel/phosphoric acid technique for tin thermal ionisation activation and a strict heating protocol for isotope ratio measurements. Instrumental mass discrimination factor has been previously determined measuring a natural tin standard solution. Spike solution has been prepared from112Sn-enriched metal and quantified by reverse isotope dilution analysis. Two sample aliquots were spiked and tin was extracted with 4.5M HCl during 25min ultrasound exposure time. Due to the complex matrix of this fly ash material, a two-step purification stage using ion-exchange chromatography was required prior TIMS analysis. Obtained results for the two sample–spike blends (10.11±0.55 and 10.50±0.64μmolg−1) are comparable, both value and uncertainty. Also a good reproducibility is observed between measurements. The proposed ID–TIMS procedure, as a primary method and due to the lack of fly ash reference materials certified for tin content, can be used to validate more routine methodologies applied to tin determination in this kind of samples.
Keywords: Tin; Isotope dilution; Thermal ionisation mass spectrometry; Ion-exchange chromatography; Fly ash
Isotope dilution–thermal ionisation mass spectrometric analysis for tin in a fly ash material by Carolina Hernández; Marta Fernández; Alberto J. Quejido; Dolores M. Sánchez; Ramón Morante; Raúl Martín (pp. 279-287).
Isotope dilution–thermal ionisation mass spectrometry (ID–TIMS) analysis has been applied to the determination of tin in a fly ash sample supplied by the EC Joint Research Centre (Ispra, Italy). The proposed procedure includes the silica gel/phosphoric acid technique for tin thermal ionisation activation and a strict heating protocol for isotope ratio measurements. Instrumental mass discrimination factor has been previously determined measuring a natural tin standard solution. Spike solution has been prepared from112Sn-enriched metal and quantified by reverse isotope dilution analysis. Two sample aliquots were spiked and tin was extracted with 4.5M HCl during 25min ultrasound exposure time. Due to the complex matrix of this fly ash material, a two-step purification stage using ion-exchange chromatography was required prior TIMS analysis. Obtained results for the two sample–spike blends (10.11±0.55 and 10.50±0.64μmolg−1) are comparable, both value and uncertainty. Also a good reproducibility is observed between measurements. The proposed ID–TIMS procedure, as a primary method and due to the lack of fly ash reference materials certified for tin content, can be used to validate more routine methodologies applied to tin determination in this kind of samples.
Keywords: Tin; Isotope dilution; Thermal ionisation mass spectrometry; Ion-exchange chromatography; Fly ash
Optimization of transmission near infrared spectrometry procedures for quality control of pesticide formulations by Sergio Armenta; Salvador Garrigues; Miguel de la Guardia (pp. 288-297).
The use of different response functions to be optimized in the frame of the use of near infrared spectrometry for quality control of active principles in agrochemical formulations has been evaluated. Both, simple functions, based on parameters like sensitivity, repeatability, accuracy, signal to noise ratio, limit of detection or sample throughput, and a complex function, considering all the aforementioned aspects, were employed in the development of a new method for Iprodione determination in agrochemicals. Optimization strategies were based on the previous screening of the most important instrumental factors like number of cumulated scans, nominal resolution, mirror velocity and zero filling factor, based on a two-level full factorial design and on the search for the optimum conditions using central composite designs. Data found evidenced the influence of the response function on the optimum values of experimental conditions and could be employed as a general guide to evaluate the experimental factors in routine use of near infrared spectrometry. Finally the optimized method for Iprodione has been applied to the determination of Diuron and results found compared with those obtained by a conventional approach.
Keywords: Optimization functions; Near infrared; Partial least squares calibration; Pesticide formulations
Optimization of transmission near infrared spectrometry procedures for quality control of pesticide formulations by Sergio Armenta; Salvador Garrigues; Miguel de la Guardia (pp. 288-297).
The use of different response functions to be optimized in the frame of the use of near infrared spectrometry for quality control of active principles in agrochemical formulations has been evaluated. Both, simple functions, based on parameters like sensitivity, repeatability, accuracy, signal to noise ratio, limit of detection or sample throughput, and a complex function, considering all the aforementioned aspects, were employed in the development of a new method for Iprodione determination in agrochemicals. Optimization strategies were based on the previous screening of the most important instrumental factors like number of cumulated scans, nominal resolution, mirror velocity and zero filling factor, based on a two-level full factorial design and on the search for the optimum conditions using central composite designs. Data found evidenced the influence of the response function on the optimum values of experimental conditions and could be employed as a general guide to evaluate the experimental factors in routine use of near infrared spectrometry. Finally the optimized method for Iprodione has been applied to the determination of Diuron and results found compared with those obtained by a conventional approach.
Keywords: Optimization functions; Near infrared; Partial least squares calibration; Pesticide formulations
Validation and uncertainty assessment of rapid extraction and clean-up methods for the determination of 16 organochlorine pesticide residues in vegetables by Serpil Yenisoy-Karakaş (pp. 298-307).
Rapid and practical extraction methods were developed using dichloromethane and ethyl acetate for the routine determination of 16 organochlorine pesticide residues and applied to approximately 30 fresh vegetables (tomato, cucumber and pepper) by using GC-ECD. The procedures were validated. Measurement uncertainties were calculated by applying bottom-up approach. The average recoveries obtained for each pesticide ranged between 65 and 102% at three fortification levels. The uncertainties of the analytical methods were lower than 21 and 16% with and without recovery correction, respectively. The calculated limits of detection and quantification were typically less than 1ngg−1 that were much lower than the maximum residue levels.
Keywords: Vegetables; Residual pesticides; Method validation; Extraction; Uncertainty
Validation and uncertainty assessment of rapid extraction and clean-up methods for the determination of 16 organochlorine pesticide residues in vegetables by Serpil Yenisoy-Karakaş (pp. 298-307).
Rapid and practical extraction methods were developed using dichloromethane and ethyl acetate for the routine determination of 16 organochlorine pesticide residues and applied to approximately 30 fresh vegetables (tomato, cucumber and pepper) by using GC-ECD. The procedures were validated. Measurement uncertainties were calculated by applying bottom-up approach. The average recoveries obtained for each pesticide ranged between 65 and 102% at three fortification levels. The uncertainties of the analytical methods were lower than 21 and 16% with and without recovery correction, respectively. The calculated limits of detection and quantification were typically less than 1ngg−1 that were much lower than the maximum residue levels.
Keywords: Vegetables; Residual pesticides; Method validation; Extraction; Uncertainty
Evaluation of calix-crown ionophores for selective separation of radio-cesium from acidic nuclear waste solution by P.K. Mohapatra; S.A. Ansari; A. Sarkar; A. Bhattacharyya; V.K. Manchanda (pp. 308-314).
Extraction of Cs-137 from nitric acid was carried out using nitrobenzene solutions of calix-crowns such as calix[4]arene-bis(crown-6) (CC-A), calix[4]arene-bis(benzo crown-6) (CC-B) and calix[4]arene-bis(napthocrown-6) (CC-C). CC-C was found to be superior extractant for Cs(I) as compared to the other two calix-crown ligands used in the present study. The effect of diluent on the extraction of Cs(I) indicated the trend: nitrobenzene>dichloroethane>chloroform>decanol≫carbon tetrachloride∼ n-hexane∼toluene. Subsequently, the studies were carried out with nitrobenzene solutions of the calix-crown ligands (mainly CC-C) on the effects of (a) aqueous phase acidity, (b) ligand concentration, and (c) cesium concentration on Cs extraction from nitric acid media. Conditions for quantitative extraction and stripping were optimized and the extracted species conformed to {[CsL]+·[NO3]−· nH2O}. Selectivity studies were carried out using an irradiated natural U target involving tracer amount of fission products activities. Extraction of Cs(I) from a synthetic high level waste solution was also carried out. The promising results obtained in the present studies indicate possible use of the calix-crown ligand for Cs(I) recovery from the acidic high level waste.
Keywords: Abbreviations; Alamine 336; tri-caproyl amine; 18C6; 18 crown 6; CC-A; calix[4]arene-bis(crown-6); CC-B; calix[4]arene-bis(benzocrown-6); CC-C; calix[4]arene-bis(napthocrown-6); CSSX; caustic side solvent extraction; D.P.; Schmidt's diluent parameter; DTBB18C6; di-; tert; -butyl benzo 18 crown 6; HLW; high level waste; L; calix-crown ligand; MIBK; methyl; iso; -butyl ketone; PHWR; pressurised heavy water reactor; δ; Hildebrand's solubility parametersCesium; Solvent extraction; Nuclear waste; Calix-crown
Evaluation of calix-crown ionophores for selective separation of radio-cesium from acidic nuclear waste solution by P.K. Mohapatra; S.A. Ansari; A. Sarkar; A. Bhattacharyya; V.K. Manchanda (pp. 308-314).
Extraction of Cs-137 from nitric acid was carried out using nitrobenzene solutions of calix-crowns such as calix[4]arene-bis(crown-6) (CC-A), calix[4]arene-bis(benzo crown-6) (CC-B) and calix[4]arene-bis(napthocrown-6) (CC-C). CC-C was found to be superior extractant for Cs(I) as compared to the other two calix-crown ligands used in the present study. The effect of diluent on the extraction of Cs(I) indicated the trend: nitrobenzene>dichloroethane>chloroform>decanol≫carbon tetrachloride∼ n-hexane∼toluene. Subsequently, the studies were carried out with nitrobenzene solutions of the calix-crown ligands (mainly CC-C) on the effects of (a) aqueous phase acidity, (b) ligand concentration, and (c) cesium concentration on Cs extraction from nitric acid media. Conditions for quantitative extraction and stripping were optimized and the extracted species conformed to {[CsL]+·[NO3]−· nH2O}. Selectivity studies were carried out using an irradiated natural U target involving tracer amount of fission products activities. Extraction of Cs(I) from a synthetic high level waste solution was also carried out. The promising results obtained in the present studies indicate possible use of the calix-crown ligand for Cs(I) recovery from the acidic high level waste.
Keywords: Abbreviations; Alamine 336; tri-caproyl amine; 18C6; 18 crown 6; CC-A; calix[4]arene-bis(crown-6); CC-B; calix[4]arene-bis(benzocrown-6); CC-C; calix[4]arene-bis(napthocrown-6); CSSX; caustic side solvent extraction; D.P.; Schmidt's diluent parameter; DTBB18C6; di-; tert; -butyl benzo 18 crown 6; HLW; high level waste; L; calix-crown ligand; MIBK; methyl; iso; -butyl ketone; PHWR; pressurised heavy water reactor; δ; Hildebrand's solubility parametersCesium; Solvent extraction; Nuclear waste; Calix-crown
Handling complex effects in slurry-sampling-electrothermal atomic absorption spectrometry by multivariate calibration by M. Felipe-Sotelo; M.J. Cal-Prieto; M.P. Gómez-Carracedo; J.M. Andrade; A. Carlosena; D. Prada (pp. 315-323).
Analysis of solid samples by slurry-sampling-electrothermal atomic absorption spectrometry (SS-ETAAS) can imply spectral and chemical interferences caused by the large amount of concomitants introduced into the graphite furnace. Sometimes they cannot be solved using stabilized temperature platform furnace (STPF) conditions or typical approaches (previous sample ashing, use of chemical modifiers, etc.), which are time consuming and quite expensive. A new approach to handle interferences using multivariate calibrations (partial least squares, PLS, and artificial neural networks, ANN) is presented and exemplified with a real problem consisting on determining Sb in several solid matrices (soils, sediments and coal fly ash) as slurries by ETAAS.Experimental designs were implemented at different levels of Sb to develop the calibration matrix and assess which concomitants (seven ions were considered) modified the atomic signal mostly. They were Na+ and Ca2+ and they induced simultaneous displacement, depletion (enhancement) and broadening of the atomic peak. Here it is shown that these complex effects can be handled in a reliable, fast and cost-effective way to predict the concentration of Sb in slurry samples of several solid matrices. The method was validated predicting the concentrations of five certified reference materials (CRMs) and studying its robustness to current ETAAS problems. It is also shown that linear PLS can handle eventual non-linearities and that its results are comparable to more complex (non-linear) models, as those from ANNs.
Keywords: Electrothermal atomic absorption spectrometry; Antimony; Environmental solid sample slurries; Chemical interferences; Partial least squares; Artificial neural networks
Handling complex effects in slurry-sampling-electrothermal atomic absorption spectrometry by multivariate calibration by M. Felipe-Sotelo; M.J. Cal-Prieto; M.P. Gómez-Carracedo; J.M. Andrade; A. Carlosena; D. Prada (pp. 315-323).
Analysis of solid samples by slurry-sampling-electrothermal atomic absorption spectrometry (SS-ETAAS) can imply spectral and chemical interferences caused by the large amount of concomitants introduced into the graphite furnace. Sometimes they cannot be solved using stabilized temperature platform furnace (STPF) conditions or typical approaches (previous sample ashing, use of chemical modifiers, etc.), which are time consuming and quite expensive. A new approach to handle interferences using multivariate calibrations (partial least squares, PLS, and artificial neural networks, ANN) is presented and exemplified with a real problem consisting on determining Sb in several solid matrices (soils, sediments and coal fly ash) as slurries by ETAAS.Experimental designs were implemented at different levels of Sb to develop the calibration matrix and assess which concomitants (seven ions were considered) modified the atomic signal mostly. They were Na+ and Ca2+ and they induced simultaneous displacement, depletion (enhancement) and broadening of the atomic peak. Here it is shown that these complex effects can be handled in a reliable, fast and cost-effective way to predict the concentration of Sb in slurry samples of several solid matrices. The method was validated predicting the concentrations of five certified reference materials (CRMs) and studying its robustness to current ETAAS problems. It is also shown that linear PLS can handle eventual non-linearities and that its results are comparable to more complex (non-linear) models, as those from ANNs.
Keywords: Electrothermal atomic absorption spectrometry; Antimony; Environmental solid sample slurries; Chemical interferences; Partial least squares; Artificial neural networks