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Analytica Chimica Acta (v.582, #2)
Environmental and pharmaceutical analysis of dithiocarbamates by O.H.J. Szolar (pp. 191-200).
The current review aims at a comprehensive survey of analytical methods for the determination of dithiocarbamates (DTCs) in environmental and pharmaceutical samples. Besides parent compounds, analytical approaches for various metabolites and degradation products of DTCs are considered. Special emphasis is given to analyte stability as DTCs are considerably reactive interacting with various organic and inorganic compounds; in addition, depending on the chemical nature of the substance, DTCs are prone to oxidation and hydrolysis under alkaline and acidic conditions, respectively. The review mainly focuses on chromatography but also covers applications in electrophoresis, spectrophotometry, and biosensing.
Keywords: Dithiocarbamates; Chromatography; Environmental analysis; Pharmaceutical analysis; Review
Environmental and pharmaceutical analysis of dithiocarbamates by O.H.J. Szolar (pp. 191-200).
The current review aims at a comprehensive survey of analytical methods for the determination of dithiocarbamates (DTCs) in environmental and pharmaceutical samples. Besides parent compounds, analytical approaches for various metabolites and degradation products of DTCs are considered. Special emphasis is given to analyte stability as DTCs are considerably reactive interacting with various organic and inorganic compounds; in addition, depending on the chemical nature of the substance, DTCs are prone to oxidation and hydrolysis under alkaline and acidic conditions, respectively. The review mainly focuses on chromatography but also covers applications in electrophoresis, spectrophotometry, and biosensing.
Keywords: Dithiocarbamates; Chromatography; Environmental analysis; Pharmaceutical analysis; Review
Platinum-group element concentrations in BCR-723: A quantitative review of published analyses by Ross A. Sutherland (pp. 201-207).
BCR-723 is the only environmental certified reference material for platinum-group elements (PGEs) Pt, Pd and Rh. It has been an integral component of quality control/quality assurance procedures in environmental laboratories measuring PGEs, since 2001. Here, we present an extensive quantitative review of the published PGEs measured in BCR-723, since its introduction. A statistical examination of concentrations, measurement precision and accuracy for 25 studies is presented. Measurement typically starts with an aqua regia digestion, followed by some form of pre-concentration or separation procedure, and quantitation by ICP-MS. Use of a sample mass below the recommended value of 100mg has been shown to produce biased results for acid-based digestions or with laser ablation. Platinum is the most precisely and accurately measured PGE in BCR-723, followed by Rh, and finally by Pd. Literature precision data for all autocatalyst PGEs did not differ significantly ( α=0.05) from those obtained by the original laboratories used to certify BCR-723. Measurement accuracies for the literature tabulated PGE data did not differ significantly from zero, indicating an overall lack of directional bias. These results should be encouraging to the analytical community, but further advancements, especially for Pd quantification are required.
Keywords: Palladium; Platinum; Rhodium; Certified reference material; Concentrations; Accuracy; Precision
Platinum-group element concentrations in BCR-723: A quantitative review of published analyses by Ross A. Sutherland (pp. 201-207).
BCR-723 is the only environmental certified reference material for platinum-group elements (PGEs) Pt, Pd and Rh. It has been an integral component of quality control/quality assurance procedures in environmental laboratories measuring PGEs, since 2001. Here, we present an extensive quantitative review of the published PGEs measured in BCR-723, since its introduction. A statistical examination of concentrations, measurement precision and accuracy for 25 studies is presented. Measurement typically starts with an aqua regia digestion, followed by some form of pre-concentration or separation procedure, and quantitation by ICP-MS. Use of a sample mass below the recommended value of 100mg has been shown to produce biased results for acid-based digestions or with laser ablation. Platinum is the most precisely and accurately measured PGE in BCR-723, followed by Rh, and finally by Pd. Literature precision data for all autocatalyst PGEs did not differ significantly ( α=0.05) from those obtained by the original laboratories used to certify BCR-723. Measurement accuracies for the literature tabulated PGE data did not differ significantly from zero, indicating an overall lack of directional bias. These results should be encouraging to the analytical community, but further advancements, especially for Pd quantification are required.
Keywords: Palladium; Platinum; Rhodium; Certified reference material; Concentrations; Accuracy; Precision
Determination of metal impurities in pure hydroxides and salts by inductively coupled plasma optical emission spectrometry by Anna Krejčová; Tomáš Černohorský; Miloslav Pouzar (pp. 208-213).
A simple analytical method sufficient for the determination of Na, K, Ca, Mg, Al, B, Ba, Cd, Co, Cr, Cu, Fe, Li, Mn, Mo, Ni, Pb, Sr, V and Zn at mgkg−1 levels in pure NaOH, KOH, NaCl and KCl using the optical emission spectrometry was developed. The results of direct determination with multi-elemental aqueous standards were compared with them obtained by the internal standardisation, by the standard addition methods and with the maximal allowable contents of above-mentioned elements in pure chemicals. The method was shown to be very sensitive and exhibits following limits of detection: Na 0.90, K 3.0, Ca 0.064, Mg 0.026, Al 0.43, B 0.13, Ba 0.015, Cd 0.023, Co 0.056, Cr 0.041, Cu 0.063, Fe 0.060, Li 0.017, Mn 0.035, Mo 0.19, Ni 0.055, Pb 0.39, Sr 0.030, V 0.065 and Zn 0.043 (all in mgkg−1). The method presents a satisfactory precision (relative standard deviation 4–11%), high analytical recoveries, linear responses of at least four orders of magnitude, accuracy and low contamination susceptibility.
Keywords: Inductively coupled plasma optical emission spectrometry (ICP OES); Chloride; Hydroxide; Matrix interference; Internal standardisation
Determination of metal impurities in pure hydroxides and salts by inductively coupled plasma optical emission spectrometry by Anna Krejčová; Tomáš Černohorský; Miloslav Pouzar (pp. 208-213).
A simple analytical method sufficient for the determination of Na, K, Ca, Mg, Al, B, Ba, Cd, Co, Cr, Cu, Fe, Li, Mn, Mo, Ni, Pb, Sr, V and Zn at mgkg−1 levels in pure NaOH, KOH, NaCl and KCl using the optical emission spectrometry was developed. The results of direct determination with multi-elemental aqueous standards were compared with them obtained by the internal standardisation, by the standard addition methods and with the maximal allowable contents of above-mentioned elements in pure chemicals. The method was shown to be very sensitive and exhibits following limits of detection: Na 0.90, K 3.0, Ca 0.064, Mg 0.026, Al 0.43, B 0.13, Ba 0.015, Cd 0.023, Co 0.056, Cr 0.041, Cu 0.063, Fe 0.060, Li 0.017, Mn 0.035, Mo 0.19, Ni 0.055, Pb 0.39, Sr 0.030, V 0.065 and Zn 0.043 (all in mgkg−1). The method presents a satisfactory precision (relative standard deviation 4–11%), high analytical recoveries, linear responses of at least four orders of magnitude, accuracy and low contamination susceptibility.
Keywords: Inductively coupled plasma optical emission spectrometry (ICP OES); Chloride; Hydroxide; Matrix interference; Internal standardisation
Solid sampling-graphite furnace atomic absorption spectrometry for the direct determination of boron in plant tissues by M. Resano; J. Briceño; M. Aramendía; M.A. Belarra (pp. 214-222).
In this work, the potential of graphite furnace atomic absorption spectrometry for the direct determination of B in plant tissues has been investigated. Three certified reference materials (NIST SRM 1570a spinach leaves, NIST SRM 1573a tomato leaves and BCR CRM 679 white cabbage) were selected for this study, the goal always being to develop a fast procedure that could be robust enough to provide a satisfactory performance for all of them, without any modifications in the conditions applied.The use of a suitable chemical modifier was found to be essential for obtaining a reproducible and sufficiently sensitive signal for boron solutions. In this regard, the performance of the combination of citric acid plus W (added as a permanent modifier) was noteworthy, resulting in well-defined signal profiles, a remarkable analyte stabilization during the pyrolysis step (up to 2100°C) and minimal memory effects. This mixture of modifiers provided a good performance for the direct analysis of solid samples as well, but only if a suitable temperature program, favoring the interaction between the analyte and the modifiers, was used. Thus, such a temperature program, with two pyrolysis steps and the addition of NH4NO3 in order to carry out the in situ sample microdigestion, was optimized. Under these conditions, the peak areas obtained for both solid samples and aqueous standards were comparable.Finally, the analysis of the samples was carried out. In all cases, a good agreement with the certified values was obtained, while R.S.D. values ranged between 6 and 10%. It can be concluded that the method proposed shows significant advantages for the determination of this complicated element in solid samples such as the use of aqueous standards for calibration, a high sample throughput (20min per sample), a suitable limit of detection (0.3μgg−1) and reduced risk of analyte losses and contamination.
Keywords: Solid sampling; Graphite furnace atomic absorption spectrometry; Boron determination; Tungsten permanent modifier; Citric acid
Solid sampling-graphite furnace atomic absorption spectrometry for the direct determination of boron in plant tissues by M. Resano; J. Briceño; M. Aramendía; M.A. Belarra (pp. 214-222).
In this work, the potential of graphite furnace atomic absorption spectrometry for the direct determination of B in plant tissues has been investigated. Three certified reference materials (NIST SRM 1570a spinach leaves, NIST SRM 1573a tomato leaves and BCR CRM 679 white cabbage) were selected for this study, the goal always being to develop a fast procedure that could be robust enough to provide a satisfactory performance for all of them, without any modifications in the conditions applied.The use of a suitable chemical modifier was found to be essential for obtaining a reproducible and sufficiently sensitive signal for boron solutions. In this regard, the performance of the combination of citric acid plus W (added as a permanent modifier) was noteworthy, resulting in well-defined signal profiles, a remarkable analyte stabilization during the pyrolysis step (up to 2100°C) and minimal memory effects. This mixture of modifiers provided a good performance for the direct analysis of solid samples as well, but only if a suitable temperature program, favoring the interaction between the analyte and the modifiers, was used. Thus, such a temperature program, with two pyrolysis steps and the addition of NH4NO3 in order to carry out the in situ sample microdigestion, was optimized. Under these conditions, the peak areas obtained for both solid samples and aqueous standards were comparable.Finally, the analysis of the samples was carried out. In all cases, a good agreement with the certified values was obtained, while R.S.D. values ranged between 6 and 10%. It can be concluded that the method proposed shows significant advantages for the determination of this complicated element in solid samples such as the use of aqueous standards for calibration, a high sample throughput (20min per sample), a suitable limit of detection (0.3μgg−1) and reduced risk of analyte losses and contamination.
Keywords: Solid sampling; Graphite furnace atomic absorption spectrometry; Boron determination; Tungsten permanent modifier; Citric acid
Enantioseparation of phenotiazines by affinity electrokinetic chromatography using human serum albumin as chiral selector by María Amparo Martínez-Gómez; Salvador Sagrado; Rosa María Villanueva-Camañas; Maria José Medina-Hernández (pp. 223-228).
Nowadays, there is a special interest within the pharmaceutical laboratories to develop single enantiomer formulations and consequently a need for analytical methods to determine the enantiomeric purity of drugs. The present paper deals with the enantiomeric separation of promethazine and trimeprazine enantiomers by affinity electrokinetic chromatography (AEKC)-partial filling technique using human serum albumin (HSA) as chiral selector. A multivariate optimization of the most critical experimental variables in enantioresolution, running pH, HSA concentration and plug length, is carried out to obtain enantioresolution of promethazine and trimeprazine. The estimated maximum and optimum resolution of trimeprazine and prometazine enantiomers (Rs=1.74 and 2.01, respectively) corresponded to the following experimental conditions: pH 7.5; [HSA] 170μM and plug length 190s and pH 7.6; [HSA] 170μM and plug length 170s, for trimeprazine and prometazine, respectively. The developed methodologies were applied for the enantiomeric quality control of promethazine and trimeprazine enantiomers in commercially available pharmaceutical formulations. Resolution, accuracy, reproducibility, cost and sample throughput of the proposed methodologies make it suitable for quality control of the enantiomeric composition of promethazine and trimeprazine in pharmaceutical preparations.
Keywords: Affinity electrokinetic chromatography; Partial filling technique; Human serum albumin; Promethazine enantiomers; Trimeprazine enantiomers; Enantiomeric quality control; Pharmaceutical preparations
Enantioseparation of phenotiazines by affinity electrokinetic chromatography using human serum albumin as chiral selector by María Amparo Martínez-Gómez; Salvador Sagrado; Rosa María Villanueva-Camañas; Maria José Medina-Hernández (pp. 223-228).
Nowadays, there is a special interest within the pharmaceutical laboratories to develop single enantiomer formulations and consequently a need for analytical methods to determine the enantiomeric purity of drugs. The present paper deals with the enantiomeric separation of promethazine and trimeprazine enantiomers by affinity electrokinetic chromatography (AEKC)-partial filling technique using human serum albumin (HSA) as chiral selector. A multivariate optimization of the most critical experimental variables in enantioresolution, running pH, HSA concentration and plug length, is carried out to obtain enantioresolution of promethazine and trimeprazine. The estimated maximum and optimum resolution of trimeprazine and prometazine enantiomers (Rs=1.74 and 2.01, respectively) corresponded to the following experimental conditions: pH 7.5; [HSA] 170μM and plug length 190s and pH 7.6; [HSA] 170μM and plug length 170s, for trimeprazine and prometazine, respectively. The developed methodologies were applied for the enantiomeric quality control of promethazine and trimeprazine enantiomers in commercially available pharmaceutical formulations. Resolution, accuracy, reproducibility, cost and sample throughput of the proposed methodologies make it suitable for quality control of the enantiomeric composition of promethazine and trimeprazine in pharmaceutical preparations.
Keywords: Affinity electrokinetic chromatography; Partial filling technique; Human serum albumin; Promethazine enantiomers; Trimeprazine enantiomers; Enantiomeric quality control; Pharmaceutical preparations
Detection of indomethacin by high-performance liquid chromatography with in situ electrogenerated Mn(III) chemiluminescence detection by Yantu Zhang; Zhujun Zhang; Guangcai Qi; Yonghua Sun; Yue Wei; Hongyan Ma (pp. 229-234).
The determination of indomethacin (INM) in pharmaceutical and biological samples by means of high-performance liquid chromatography (HPLC) with in situ electrogenerated Mn(III) chemiluminescence (CL) detection was proposed. The method was based on the direct CL reaction of INM and Mn(III), which was in situ electrogenerated by constant current electrolysis. The chromatographic separation was carried out on Nucleosil RP-C18 column (250mm×4.6mm; i.d., 5μm; pore size, 100Å) at 20°C. The mobile phase consisted of methanol:water:acetic acid=67:33:0.1 solution. At a flow rate of 1.0mLmin−1, the total run time was 10min. The effects of several parameters on the HPLC resolution and CL emission were studied systematically. Under the optimal conditions, a linear range from 0.01 to 10μgmL−1( R2=0.9991), and a detection limit of 8ngmL−1 (signal-to-noise ratio=3) for INM were achieved. The relative standard deviations (R.S.D.) for 0.1μgmL−1 INM were 2.2% within a day ( n=11) and 3.0% on 5 consecutive days ( n=6), respectively. The recovery of INM from urine samples was more than 92%. The applicability of the method for the analysis of pharmaceutical and biological samples was examined.
Keywords: Indomethacin; Chemiluminescence; Electrogenerated Mn(III); High-performance liquid chromatography
Detection of indomethacin by high-performance liquid chromatography with in situ electrogenerated Mn(III) chemiluminescence detection by Yantu Zhang; Zhujun Zhang; Guangcai Qi; Yonghua Sun; Yue Wei; Hongyan Ma (pp. 229-234).
The determination of indomethacin (INM) in pharmaceutical and biological samples by means of high-performance liquid chromatography (HPLC) with in situ electrogenerated Mn(III) chemiluminescence (CL) detection was proposed. The method was based on the direct CL reaction of INM and Mn(III), which was in situ electrogenerated by constant current electrolysis. The chromatographic separation was carried out on Nucleosil RP-C18 column (250mm×4.6mm; i.d., 5μm; pore size, 100Å) at 20°C. The mobile phase consisted of methanol:water:acetic acid=67:33:0.1 solution. At a flow rate of 1.0mLmin−1, the total run time was 10min. The effects of several parameters on the HPLC resolution and CL emission were studied systematically. Under the optimal conditions, a linear range from 0.01 to 10μgmL−1( R2=0.9991), and a detection limit of 8ngmL−1 (signal-to-noise ratio=3) for INM were achieved. The relative standard deviations (R.S.D.) for 0.1μgmL−1 INM were 2.2% within a day ( n=11) and 3.0% on 5 consecutive days ( n=6), respectively. The recovery of INM from urine samples was more than 92%. The applicability of the method for the analysis of pharmaceutical and biological samples was examined.
Keywords: Indomethacin; Chemiluminescence; Electrogenerated Mn(III); High-performance liquid chromatography
Quantitative structure-retention relationships of pesticides in reversed-phase high-performance liquid chromatography by Massimiliano Aschi; Angelo Antonio D’Archivio; Maria Anna Maggi; Pietro Mazzeo; Fabrizio Ruggieri (pp. 235-242).
In this paper, a quantitative structure–retention relationships (QSRR) method is employed to predict the retention behaviour of pesticides in reversed-phase high-performance liquid chromatography (HPLC). A six-parameter nonlinear model is developed by means of a feed-forward artificial neural network (ANN) with back-propagation learning rule. Accurate description of the retention factors of 26 compounds including commonly used insecticides, herbicides and fungicides and some metabolites is successfully achieved. In addition to the acetonitrile content, included to describe composition of the water–acetonitrile mobile phase, the octanol–water partition coefficient (from literature) and four quantum chemical descriptors are considered to account for the effect of solute structure on the retention. These are: the total dipole moment, the mean polarizability, the anisotropy of polarizability and a descriptor of hydrogen bonding ability based on the atomic charges on hydrogen bond donor and acceptor chemical functionalities. The proposed nonlinear QSRR model exhibits a high degree of correlation between observed and computed retention factors and a good predictive performance in wide range of mobile phase composition (40–65%, v/v acetonitrile) that supports its application for the prediction of the chromatographic behaviour of unknown pesticides. A multilinear regression model based on the same six descriptors shows a significantly worse predictive capability.
Keywords: Quantitative structure-retention relationships; Quantum chemical descriptors; Artificial neural network; Reversed-phase high-performance liquid chromatography; Pesticides; Chromatographic optimization
Quantitative structure-retention relationships of pesticides in reversed-phase high-performance liquid chromatography by Massimiliano Aschi; Angelo Antonio D’Archivio; Maria Anna Maggi; Pietro Mazzeo; Fabrizio Ruggieri (pp. 235-242).
In this paper, a quantitative structure–retention relationships (QSRR) method is employed to predict the retention behaviour of pesticides in reversed-phase high-performance liquid chromatography (HPLC). A six-parameter nonlinear model is developed by means of a feed-forward artificial neural network (ANN) with back-propagation learning rule. Accurate description of the retention factors of 26 compounds including commonly used insecticides, herbicides and fungicides and some metabolites is successfully achieved. In addition to the acetonitrile content, included to describe composition of the water–acetonitrile mobile phase, the octanol–water partition coefficient (from literature) and four quantum chemical descriptors are considered to account for the effect of solute structure on the retention. These are: the total dipole moment, the mean polarizability, the anisotropy of polarizability and a descriptor of hydrogen bonding ability based on the atomic charges on hydrogen bond donor and acceptor chemical functionalities. The proposed nonlinear QSRR model exhibits a high degree of correlation between observed and computed retention factors and a good predictive performance in wide range of mobile phase composition (40–65%, v/v acetonitrile) that supports its application for the prediction of the chromatographic behaviour of unknown pesticides. A multilinear regression model based on the same six descriptors shows a significantly worse predictive capability.
Keywords: Quantitative structure-retention relationships; Quantum chemical descriptors; Artificial neural network; Reversed-phase high-performance liquid chromatography; Pesticides; Chromatographic optimization
Fast analysis of soy isoflavones by high-performance liquid chromatography with monolithic columns by Mauricio A. Rostagno; Miguel Palma; Carmelo G. Barroso (pp. 243-249).
A fast method using high-performance liquid chromatography based on two monolithic columns has been developed for the simultaneous determination of isoflavones extracted from soybeans and derived foods. The 12 main isoflavones were resolved in 10min in two coupled monolithic columns working at 35°C using a elution gradient of acidified water (0.1% acetic acid) and methanol (0.1% acetic acid) at a flow rate of 5mLmin−1. Retention time and relative area standard deviations were below 1% for all isoflavones. The method developed was successfully applied to several soy food samples and spiked samples. Total isoflavone concentration in sampled soy foods ranged from 34.28mgL−1 to 4.29mgg−1.
Keywords: High-performance liquid chromatography; Monolithic columns; Isoflavones; Soybeans; Soy foods
Fast analysis of soy isoflavones by high-performance liquid chromatography with monolithic columns by Mauricio A. Rostagno; Miguel Palma; Carmelo G. Barroso (pp. 243-249).
A fast method using high-performance liquid chromatography based on two monolithic columns has been developed for the simultaneous determination of isoflavones extracted from soybeans and derived foods. The 12 main isoflavones were resolved in 10min in two coupled monolithic columns working at 35°C using a elution gradient of acidified water (0.1% acetic acid) and methanol (0.1% acetic acid) at a flow rate of 5mLmin−1. Retention time and relative area standard deviations were below 1% for all isoflavones. The method developed was successfully applied to several soy food samples and spiked samples. Total isoflavone concentration in sampled soy foods ranged from 34.28mgL−1 to 4.29mgg−1.
Keywords: High-performance liquid chromatography; Monolithic columns; Isoflavones; Soybeans; Soy foods
A comparative study of the performance of acetonitrile and methanol in the multi-linear gradient separation of proteic primary amino acids by V. Concha-Herrera; J.R. Torres-Lapasió; G. Vivó-Truyols; M.C. García-Álvarez-Coque (pp. 250-258).
The performance of the separation of proteic primary amino acids using multi-linear gradients of acetonitrile and methanol was studied under an experimental-design basis, using an Inertsil ODS-3 column and pre-column derivatization with o-phthaldialdehyde (OPA) and N-acetyl-l-cysteine (NAC). Elution strength, peak properties, resolution, and analysis time, were examined. The optimal separation was established through modeling, using information obtained from isocratic data. By optimizing the separation with gradients of increasing complexity, acceptable resolution was possible, being glycine/threonine the critical pair. Multi-criteria decision-making (Derringer desirabilities) was applied to balance resolution and analysis time. The more favorable peak distribution for methanol gradients allowed a larger reduction of analysis times, keeping satisfactory resolution, but its smaller elution strength forces the use of concentrations significantly larger. Methanol is, however, less toxic, and the final cost is similar for both solvents.
Keywords: Proteic primary amino acids; Reversed-phase liquid chromatography; Acetonitrile; Methanol; Separation performance; Multi-linear gradients
A comparative study of the performance of acetonitrile and methanol in the multi-linear gradient separation of proteic primary amino acids by V. Concha-Herrera; J.R. Torres-Lapasió; G. Vivó-Truyols; M.C. García-Álvarez-Coque (pp. 250-258).
The performance of the separation of proteic primary amino acids using multi-linear gradients of acetonitrile and methanol was studied under an experimental-design basis, using an Inertsil ODS-3 column and pre-column derivatization with o-phthaldialdehyde (OPA) and N-acetyl-l-cysteine (NAC). Elution strength, peak properties, resolution, and analysis time, were examined. The optimal separation was established through modeling, using information obtained from isocratic data. By optimizing the separation with gradients of increasing complexity, acceptable resolution was possible, being glycine/threonine the critical pair. Multi-criteria decision-making (Derringer desirabilities) was applied to balance resolution and analysis time. The more favorable peak distribution for methanol gradients allowed a larger reduction of analysis times, keeping satisfactory resolution, but its smaller elution strength forces the use of concentrations significantly larger. Methanol is, however, less toxic, and the final cost is similar for both solvents.
Keywords: Proteic primary amino acids; Reversed-phase liquid chromatography; Acetonitrile; Methanol; Separation performance; Multi-linear gradients
Determination of less polar heterocyclic amines in meat extracts by Aurora Martín-Calero; Juan H. Ayala; Venerando González; Ana M. Afonso (pp. 259-266).
A procedure for the determination of less polar heterocyclic amines in meat extracts using solid phase microextraction (SPME) coupled to high-performance liquid chromatography (HPLC) with fluorescence detection is presented. Analytes were first extracted from the samples using methanol/NaOH by an ultrasound-assisted method, and then concentrated on a Carbowax-templated resin (CW-TPR) SPME fiber. The extraction conditions such as extractant mixture composition, extraction time and extractions number, were optimized and the need of an extract freezing step previous to SPME is discussed. The detection limits under optimal conditions are in the range of 0.28–1.1ngg−1. The method was applied to the determination of less polar heterocyclic amines in four commercial meat extracts. Recovery values obtained are higher than 60% for the majority of amines.
Keywords: Solid-phase microextraction; High-performance liquid chromatography; Experimental design; Heterocyclic amines; Food analysis
Determination of less polar heterocyclic amines in meat extracts by Aurora Martín-Calero; Juan H. Ayala; Venerando González; Ana M. Afonso (pp. 259-266).
A procedure for the determination of less polar heterocyclic amines in meat extracts using solid phase microextraction (SPME) coupled to high-performance liquid chromatography (HPLC) with fluorescence detection is presented. Analytes were first extracted from the samples using methanol/NaOH by an ultrasound-assisted method, and then concentrated on a Carbowax-templated resin (CW-TPR) SPME fiber. The extraction conditions such as extractant mixture composition, extraction time and extractions number, were optimized and the need of an extract freezing step previous to SPME is discussed. The detection limits under optimal conditions are in the range of 0.28–1.1ngg−1. The method was applied to the determination of less polar heterocyclic amines in four commercial meat extracts. Recovery values obtained are higher than 60% for the majority of amines.
Keywords: Solid-phase microextraction; High-performance liquid chromatography; Experimental design; Heterocyclic amines; Food analysis
Highly selective electrogenerated chemiluminescence (ECL) for sulfide ion determination at multi-wall carbon nanotubes-modified graphite electrode by Rongfu Huang; Xingwang Zheng; Yingjuan Qu (pp. 267-274).
In the present work, a novel method for immobilization of carbon nanotubes (CNTs) on the surface of graphite electrode was proposed. We further found that superoxide ion was electrogenerated on this CNTs-modified electrode, which can react with sulfide ion combing with a weak but fast electrogenerated chemiluminescence (ECL) emission, and this weak ECL signal could be enhanced by the oxidative products of rhodamine B. In addition, the rate constant of this electrochemical reaction k0 was investigated and confirmed that the speed of electrogenerating superoxide ion was in accordance with the subsequent fast CL reaction. Thus, the fast CL reaction of superoxide ion with target brought in the possibility of high selectivity based on time-resolved, relative to other interferences. Based on these findings, an excellently selective and highly sensitive ECL method for sulfide ion was developed. Under the optimum conditions, the enhancing ECL signals were linear with the sulfide ion concentration in the range from 6.0×10−10 to 1.0×10−8molL−1, and a 2.0×10−10molL−1 detection limits (3 σ) was achieved. In addition, the proposed method was successfully used to detect sulfide ion in environmental water samples.
Keywords: Electrogenerating superoxide ion; Chemiluminescence; Multi-wall carbon nanotubes; Sulfide ion determination; Modified graphite electrode
Highly selective electrogenerated chemiluminescence (ECL) for sulfide ion determination at multi-wall carbon nanotubes-modified graphite electrode by Rongfu Huang; Xingwang Zheng; Yingjuan Qu (pp. 267-274).
In the present work, a novel method for immobilization of carbon nanotubes (CNTs) on the surface of graphite electrode was proposed. We further found that superoxide ion was electrogenerated on this CNTs-modified electrode, which can react with sulfide ion combing with a weak but fast electrogenerated chemiluminescence (ECL) emission, and this weak ECL signal could be enhanced by the oxidative products of rhodamine B. In addition, the rate constant of this electrochemical reaction k0 was investigated and confirmed that the speed of electrogenerating superoxide ion was in accordance with the subsequent fast CL reaction. Thus, the fast CL reaction of superoxide ion with target brought in the possibility of high selectivity based on time-resolved, relative to other interferences. Based on these findings, an excellently selective and highly sensitive ECL method for sulfide ion was developed. Under the optimum conditions, the enhancing ECL signals were linear with the sulfide ion concentration in the range from 6.0×10−10 to 1.0×10−8molL−1, and a 2.0×10−10molL−1 detection limits (3 σ) was achieved. In addition, the proposed method was successfully used to detect sulfide ion in environmental water samples.
Keywords: Electrogenerating superoxide ion; Chemiluminescence; Multi-wall carbon nanotubes; Sulfide ion determination; Modified graphite electrode
An improved electrochemiluminescence polymerase chain reaction method for highly sensitive detection of plant viruses by Ya-bing Tang; Da Xing; De-bin Zhu; Jin-feng Liu (pp. 275-280).
Recently, we have reported an electrochemiluminescence polymerase chain reaction (ECL-PCR) method for detection of genetically modified organisms. The ECL-PCR method was further improved in the current study by introducing a multi-purpose nucleic acid sequence that was specific to the tris(bipyridine) ruthenium (TBR) labeled probe, into the 5′ terminal of the primers. The method was applied to detect plant viruses. Conserved sequence of the plant viruses was amplified by PCR. The product was hybridized with a biotin labeled probe and a TBR labeled probe. The hybridization product was separated by streptavidin-coated magnetic beads, and detected by measuring the ECL signals of the TBR labeled. Under the optimized conditions, the experiment results show that the detection limit is 50fmol of PCR products, and the signal-to-noise ratio is in excess of 14.6. The method was used to detect banana streak virus, banana bunchy top virus, and papaya leaf curl virus. The experiment results show that this method could reliably identity viruses infected plant samples. The improved ECL-PCR approach has higher sensitivity and lower cost than previous approach. It can effectively detect the plant viruses with simplicity, stability, and high sensitivity.
Keywords: Electrochemiluminescence; Polymerase chain reaction; Plant viruses; Tris(bipyridine) ruthenium-probe; Biotin-probe
An improved electrochemiluminescence polymerase chain reaction method for highly sensitive detection of plant viruses by Ya-bing Tang; Da Xing; De-bin Zhu; Jin-feng Liu (pp. 275-280).
Recently, we have reported an electrochemiluminescence polymerase chain reaction (ECL-PCR) method for detection of genetically modified organisms. The ECL-PCR method was further improved in the current study by introducing a multi-purpose nucleic acid sequence that was specific to the tris(bipyridine) ruthenium (TBR) labeled probe, into the 5′ terminal of the primers. The method was applied to detect plant viruses. Conserved sequence of the plant viruses was amplified by PCR. The product was hybridized with a biotin labeled probe and a TBR labeled probe. The hybridization product was separated by streptavidin-coated magnetic beads, and detected by measuring the ECL signals of the TBR labeled. Under the optimized conditions, the experiment results show that the detection limit is 50fmol of PCR products, and the signal-to-noise ratio is in excess of 14.6. The method was used to detect banana streak virus, banana bunchy top virus, and papaya leaf curl virus. The experiment results show that this method could reliably identity viruses infected plant samples. The improved ECL-PCR approach has higher sensitivity and lower cost than previous approach. It can effectively detect the plant viruses with simplicity, stability, and high sensitivity.
Keywords: Electrochemiluminescence; Polymerase chain reaction; Plant viruses; Tris(bipyridine) ruthenium-probe; Biotin-probe
Fluorescence for the ultrasensitive detection of peptides with functionalized nano-ZnS by Xudong Chen; Yeping Dong; Li Fan; Dacheng Yang (pp. 281-287).
The fluorescence emitted by the functionalized ZnS nanocrystal at 440nm could be efficiently enhanced or quenched when various peptides were added. The mechanism of the fluorescence enchancement and quenching of ZnS nanocrystals was discussed. The binding constant and numbers of binding sites was obtained from the Scatchard plot. The change of fluorescence intensity was in proportion to the concentration of peptides. The limits of detection were in range of 0.011–0.028μgmL−1. Application results to synthetic samples showed simplicity, rapidity, high sensitivity and satisfactory reproducibility of the presented method. Measurements of real samples also give satisfactory results which were in good agreement with those obtained using high performance liquid chromatograph (HPLC) and liquid chromatograph–mass spectrograph (LC–MS) methods.
Keywords: Peptides; Nanocrystals; Fluorescence; Determination
Fluorescence for the ultrasensitive detection of peptides with functionalized nano-ZnS by Xudong Chen; Yeping Dong; Li Fan; Dacheng Yang (pp. 281-287).
The fluorescence emitted by the functionalized ZnS nanocrystal at 440nm could be efficiently enhanced or quenched when various peptides were added. The mechanism of the fluorescence enchancement and quenching of ZnS nanocrystals was discussed. The binding constant and numbers of binding sites was obtained from the Scatchard plot. The change of fluorescence intensity was in proportion to the concentration of peptides. The limits of detection were in range of 0.011–0.028μgmL−1. Application results to synthetic samples showed simplicity, rapidity, high sensitivity and satisfactory reproducibility of the presented method. Measurements of real samples also give satisfactory results which were in good agreement with those obtained using high performance liquid chromatograph (HPLC) and liquid chromatograph–mass spectrograph (LC–MS) methods.
Keywords: Peptides; Nanocrystals; Fluorescence; Determination
Enhanced synchronous spectrofluorimetric determination of aflatoxin B1 in pistachio samples using multivariate analysis by Mohammad Aghamohammadi; Javad Hashemi; Gholamreza Asadi Kram; Naader Alizadeh (pp. 288-294).
The determination of aflatoxin B1 (AFB1) in pistachio has been accomplished by normal and synchronous fluorimetry in combination with some multivariate calibration methods and derivative techniques. Extending the two-dimensional synchronous fluorescence scan to a three-dimensional total synchronous fluorescence scan was used to obtain the optimized Δ λ for AFB1 in pistachio sample. The methods are based on the enhanced fluorescence of AFB1 by β-cyclodextrine in 10% (v/v) methanol–water solution. Twenty-six pistachio samples containing AFB1 in the range 0–15ppb were used as calibration set. Eighteen combinational methods were tested to make best model for prediction of AFB1 and finally best results obtained using a method based on synchronous fluorimetry in combination with multiple linear regressions (MLR). For concentrations ranging from 0 to 15ppb of AFB1 in 22 pistachio samples as prediction set, the values of root mean square difference (RMSD) and relative error of prediction (REP) using MLR were 0.328 and 4.453%, respectively were observed. Two naturally contaminated pistachio samples were analyzed by synchronous fluorimetry using MLR and compared with HPLC results.
Keywords: Aflatoxin B; 1; Pistachio; β-Cyclodextrine; Synchronous fluorimetry; Multiple linear regressions; Partial least-squares; Principle components analysis
Enhanced synchronous spectrofluorimetric determination of aflatoxin B1 in pistachio samples using multivariate analysis by Mohammad Aghamohammadi; Javad Hashemi; Gholamreza Asadi Kram; Naader Alizadeh (pp. 288-294).
The determination of aflatoxin B1 (AFB1) in pistachio has been accomplished by normal and synchronous fluorimetry in combination with some multivariate calibration methods and derivative techniques. Extending the two-dimensional synchronous fluorescence scan to a three-dimensional total synchronous fluorescence scan was used to obtain the optimized Δ λ for AFB1 in pistachio sample. The methods are based on the enhanced fluorescence of AFB1 by β-cyclodextrine in 10% (v/v) methanol–water solution. Twenty-six pistachio samples containing AFB1 in the range 0–15ppb were used as calibration set. Eighteen combinational methods were tested to make best model for prediction of AFB1 and finally best results obtained using a method based on synchronous fluorimetry in combination with multiple linear regressions (MLR). For concentrations ranging from 0 to 15ppb of AFB1 in 22 pistachio samples as prediction set, the values of root mean square difference (RMSD) and relative error of prediction (REP) using MLR were 0.328 and 4.453%, respectively were observed. Two naturally contaminated pistachio samples were analyzed by synchronous fluorimetry using MLR and compared with HPLC results.
Keywords: Aflatoxin B; 1; Pistachio; β-Cyclodextrine; Synchronous fluorimetry; Multiple linear regressions; Partial least-squares; Principle components analysis
Rapid discrimination of single-nucleotide mismatches using a microfluidic device with monolayered beads by Johnson Kian-Kok Ng; Hanhua Feng; Wen-Tso Liu (pp. 295-303).
A microfluidic device incorporating monolayered beads is developed for the discrimination of single-nucleotide mismatches, based on the differential dissociation kinetics between perfect match (PM) and mismatched (MM) duplexes. The monolayered beads are used as solid support for the immobilization of oligonucleotide probes containing a single-base variation. Target oligonucleotides hybridize to the probes, forming either PM duplexes or MM duplexes containing a single mismatch. Optimization studies show that PM and MM duplexes are easily discriminated based on their dissociation but not hybridization kinetics under an optimized buffer composition of 100mM NaCl and 50% formamide. Detection of single-nucleotide polymorphism (SNP) using the device is demonstrated within 8min using four probes containing all the possible single-base variants. The device can easily be modified to integrate multiplexed detection, making high-throughput SNP detection possible.
Keywords: Single-nucleotide polymorphisms (SNPs); Microfluidic device; Single-nucleotide mismatches; Microbeads; Dissociation kinetics
Rapid discrimination of single-nucleotide mismatches using a microfluidic device with monolayered beads by Johnson Kian-Kok Ng; Hanhua Feng; Wen-Tso Liu (pp. 295-303).
A microfluidic device incorporating monolayered beads is developed for the discrimination of single-nucleotide mismatches, based on the differential dissociation kinetics between perfect match (PM) and mismatched (MM) duplexes. The monolayered beads are used as solid support for the immobilization of oligonucleotide probes containing a single-base variation. Target oligonucleotides hybridize to the probes, forming either PM duplexes or MM duplexes containing a single mismatch. Optimization studies show that PM and MM duplexes are easily discriminated based on their dissociation but not hybridization kinetics under an optimized buffer composition of 100mM NaCl and 50% formamide. Detection of single-nucleotide polymorphism (SNP) using the device is demonstrated within 8min using four probes containing all the possible single-base variants. The device can easily be modified to integrate multiplexed detection, making high-throughput SNP detection possible.
Keywords: Single-nucleotide polymorphisms (SNPs); Microfluidic device; Single-nucleotide mismatches; Microbeads; Dissociation kinetics
Hierarchically imprinted organic–inorganic hybrid sorbent for selective separation of mercury ion from aqueous solution by Genhua Wu; Zhuqing Wang; Jie Wang; Chiyang He (pp. 304-310).
A new type of hierarchically organic–inorganic hybrid sorbent was prepared by a double-imprinting approach for the selective separation of Hg(II) from aqueous solution. In the imprinting process, both mercury ions and surfactant micelles (cetyltrimethylammonium bromide, CTAB) were used as templates, N-[3-(trimethoxy-silyl)propyl]ethylenediamine (TPED) as functional monomer, and tetraethoxysilane (TEOS) as cross-linking agent. The mercury ions and surfactant were removed from sorbent via acid leaching and ethanol extraction, respectively. The adsorption property and selective recognition ability of the sorbents were studied by equilibrium-adsorption method. Results showed that in the presence of Cu(II) or Cd(II) the biggest selectivity coefficient of the imprinted sorbents for Hg(II) was over 100, which is much higher than those of non-imprinted sorbents. The largest relative selectivity coefficient ( k′) of the ion-imprinted functionalized sorbent between Hg(II) and Cu(II) was over 300, and between Hg(II) and Cd(II) over 200. The uptake capacities and the selectivity coefficients of the hierarchically imprinted sorbent were much higher than those of the sorbent prepared without CTAB template. Furthermore, the new imprinted sorbent possessed a fast kinetics for the removal of Hg(II) from aqueous solution with the saturation time less than 5min, and could be used repeatedly. This sorbent has been successfully applied to the separation and determination of the trace Hg(II) in real water samples and those spiked with standards. This new sorbent can be used as an effective solid-phase extraction material for the selective preconcentration and separation of Hg(II) in environmental samples.
Keywords: Ionic imprinting; Selective recognition; Adsorption; Mercury ion
Hierarchically imprinted organic–inorganic hybrid sorbent for selective separation of mercury ion from aqueous solution by Genhua Wu; Zhuqing Wang; Jie Wang; Chiyang He (pp. 304-310).
A new type of hierarchically organic–inorganic hybrid sorbent was prepared by a double-imprinting approach for the selective separation of Hg(II) from aqueous solution. In the imprinting process, both mercury ions and surfactant micelles (cetyltrimethylammonium bromide, CTAB) were used as templates, N-[3-(trimethoxy-silyl)propyl]ethylenediamine (TPED) as functional monomer, and tetraethoxysilane (TEOS) as cross-linking agent. The mercury ions and surfactant were removed from sorbent via acid leaching and ethanol extraction, respectively. The adsorption property and selective recognition ability of the sorbents were studied by equilibrium-adsorption method. Results showed that in the presence of Cu(II) or Cd(II) the biggest selectivity coefficient of the imprinted sorbents for Hg(II) was over 100, which is much higher than those of non-imprinted sorbents. The largest relative selectivity coefficient ( k′) of the ion-imprinted functionalized sorbent between Hg(II) and Cu(II) was over 300, and between Hg(II) and Cd(II) over 200. The uptake capacities and the selectivity coefficients of the hierarchically imprinted sorbent were much higher than those of the sorbent prepared without CTAB template. Furthermore, the new imprinted sorbent possessed a fast kinetics for the removal of Hg(II) from aqueous solution with the saturation time less than 5min, and could be used repeatedly. This sorbent has been successfully applied to the separation and determination of the trace Hg(II) in real water samples and those spiked with standards. This new sorbent can be used as an effective solid-phase extraction material for the selective preconcentration and separation of Hg(II) in environmental samples.
Keywords: Ionic imprinting; Selective recognition; Adsorption; Mercury ion
Porous molecularly imprinted polymer membranes and polymeric particles by T.A. Sergeyeva; O.O. Brovko; E.V. Piletska; S.A. Piletsky; L.A. Goncharova; L.V. Karabanova; L.M. Sergeyeva; A.V. El'skaya (pp. 311-319).
Porous free-standing molecularly imprinted polymer membranes were synthesised by the method of in situ polymerisation using the principle of synthesis of interpenetrating polymer networks and tested in solid-phase extraction of triazine herbicides from aqueous solutions. Atrazine-specific MIP membranes were obtained by the UV-initiated co-polymerisation of methacrylic acid, tri(ethylene glycol) dimethacrylate, and oligourethane acrylate in the presence of a template (atrazine). Addition of oligourethane acrylate provided formation of the highly cross-linked MIP in a form of a free-standing 60μm thick flexible membrane. High water fluxes through the MIP membranes were achieved due to addition of linear polymers (polyethylene glycol Mw 20,000 and polyurethane Mw 40,000) to the initial mixture of monomers before the polymerization. As a result, typical semi-interpenetrating polymer networks (semi-IPNs) have been formed, where the cross-linked polymer was represented by the atrazine-specific molecularly imprinted polymer, while the linear one was represented by polyethylene glycol/polyurethane. Extraction of the linear polymers from the fully formed semi-IPNs resulted in formation of large pores in the membrane structure. At the same time, extraction of the template molecules lead to formation of the sites in the polymeric network, which in shape and arrangement of functional groups are complementary to atrazine. Reference polymeric membranes were prepared from the same mixture of monomers but in the absence of the template. Recognition properties of the MIP membranes were estimated in solid-phase extraction by their ability to selective re-adsorbtion of atrazine from 10−8 to 10−4M aqueous solutions. The imprinting effect was demonstrated for both types of the MIP membranes and the influence of the type of the linear compound on their recognition properties was estimated. The recognition properties of the MIP membranes were compared to those of the MIP particles of the same composition. Morphology of the MIP membranes was investigated using the SEM microscopy. High fluxes of the developed membranes together with high affinity and adsorption capability make them an attractive alternative to MIP particles in separation processes.
Keywords: Molecularly imprinted polymers; Membranes; Solid-phase extraction; Atrazine; Triazine herbicides
Porous molecularly imprinted polymer membranes and polymeric particles by T.A. Sergeyeva; O.O. Brovko; E.V. Piletska; S.A. Piletsky; L.A. Goncharova; L.V. Karabanova; L.M. Sergeyeva; A.V. El'skaya (pp. 311-319).
Porous free-standing molecularly imprinted polymer membranes were synthesised by the method of in situ polymerisation using the principle of synthesis of interpenetrating polymer networks and tested in solid-phase extraction of triazine herbicides from aqueous solutions. Atrazine-specific MIP membranes were obtained by the UV-initiated co-polymerisation of methacrylic acid, tri(ethylene glycol) dimethacrylate, and oligourethane acrylate in the presence of a template (atrazine). Addition of oligourethane acrylate provided formation of the highly cross-linked MIP in a form of a free-standing 60μm thick flexible membrane. High water fluxes through the MIP membranes were achieved due to addition of linear polymers (polyethylene glycol Mw 20,000 and polyurethane Mw 40,000) to the initial mixture of monomers before the polymerization. As a result, typical semi-interpenetrating polymer networks (semi-IPNs) have been formed, where the cross-linked polymer was represented by the atrazine-specific molecularly imprinted polymer, while the linear one was represented by polyethylene glycol/polyurethane. Extraction of the linear polymers from the fully formed semi-IPNs resulted in formation of large pores in the membrane structure. At the same time, extraction of the template molecules lead to formation of the sites in the polymeric network, which in shape and arrangement of functional groups are complementary to atrazine. Reference polymeric membranes were prepared from the same mixture of monomers but in the absence of the template. Recognition properties of the MIP membranes were estimated in solid-phase extraction by their ability to selective re-adsorbtion of atrazine from 10−8 to 10−4M aqueous solutions. The imprinting effect was demonstrated for both types of the MIP membranes and the influence of the type of the linear compound on their recognition properties was estimated. The recognition properties of the MIP membranes were compared to those of the MIP particles of the same composition. Morphology of the MIP membranes was investigated using the SEM microscopy. High fluxes of the developed membranes together with high affinity and adsorption capability make them an attractive alternative to MIP particles in separation processes.
Keywords: Molecularly imprinted polymers; Membranes; Solid-phase extraction; Atrazine; Triazine herbicides
Fish freshness detection by a computer screen photoassisted based gas sensor array by Adriano Alimelli; Giorgio Pennazza; Marco Santonico; Roberto Paolesse; Daniel Filippini; Arnaldo D’Amico; Ingemar Lundström; Corrado Di Natale (pp. 320-328).
In the last years a large number of different measurement methodologies were applied to measure the freshness of fishes. Among them the connection between freshness and headspace composition has been considered by gas chromatographic analysis and from the last two decades by a number of sensors and biosensors aimed at measuring some characteristic indicators (usually amines). More recently also the so-called artificial olfaction systems gathering together many non-specific sensors have shown a certain capability to transduce the global composition of the fish headspace capturing the differences between fresh and spoiled products. One of the main objectives related to the introduction of sensor systems with respect to the analytical methods is the claimed possibility to distribute the freshness control since sensors are expected to be “portable” and “simple”. In spite of these objectives, until now sensor systems did not result in any tool that may be broadly distributed. In this paper, we present a chemical sensor array where the optical features of layers of chemicals, sensitive to volatile compounds typical of spoilage processes in fish, are interrogated by a very simple platform based on a computer screen and a web cam. An array of metalloporphyrins is here used to classify fillets of thawed fishes according to their storage days and to monitor the spoilage in filleted anchovies for a time of 8h. Results indicate a complete identification of the storage days of thawed fillets and a determination of the storage time of anchovies held at room temperature with a root mean square error of validation of about 30min.The optical system produces a sort of spectral fingerprint containing information about both the absorbance and the emission of the sensitive layer. The system here illustrated, based on computer peripherals, can be easily scaled to any device endowed with a programmable screen and a camera such as cellular phones offering for the first time the possibility to fulfil the sensor expectation of diffused and efficient analytical capabilities.
Keywords: Fish freshness; Optical sensors; Sensor array; Chemometrics
Fish freshness detection by a computer screen photoassisted based gas sensor array by Adriano Alimelli; Giorgio Pennazza; Marco Santonico; Roberto Paolesse; Daniel Filippini; Arnaldo D’Amico; Ingemar Lundström; Corrado Di Natale (pp. 320-328).
In the last years a large number of different measurement methodologies were applied to measure the freshness of fishes. Among them the connection between freshness and headspace composition has been considered by gas chromatographic analysis and from the last two decades by a number of sensors and biosensors aimed at measuring some characteristic indicators (usually amines). More recently also the so-called artificial olfaction systems gathering together many non-specific sensors have shown a certain capability to transduce the global composition of the fish headspace capturing the differences between fresh and spoiled products. One of the main objectives related to the introduction of sensor systems with respect to the analytical methods is the claimed possibility to distribute the freshness control since sensors are expected to be “portable” and “simple”. In spite of these objectives, until now sensor systems did not result in any tool that may be broadly distributed. In this paper, we present a chemical sensor array where the optical features of layers of chemicals, sensitive to volatile compounds typical of spoilage processes in fish, are interrogated by a very simple platform based on a computer screen and a web cam. An array of metalloporphyrins is here used to classify fillets of thawed fishes according to their storage days and to monitor the spoilage in filleted anchovies for a time of 8h. Results indicate a complete identification of the storage days of thawed fillets and a determination of the storage time of anchovies held at room temperature with a root mean square error of validation of about 30min.The optical system produces a sort of spectral fingerprint containing information about both the absorbance and the emission of the sensitive layer. The system here illustrated, based on computer peripherals, can be easily scaled to any device endowed with a programmable screen and a camera such as cellular phones offering for the first time the possibility to fulfil the sensor expectation of diffused and efficient analytical capabilities.
Keywords: Fish freshness; Optical sensors; Sensor array; Chemometrics
Development of a biosensor for caffeine by V.R. Sarath Babu; S. Patra; N.G. Karanth; M.A. Kumar; M.S. Thakur (pp. 329-334).
We have utilized a microbe, which can degrade caffeine to develop an Amperometric biosensor for determination of caffeine in solutions. Whole cells of Pseudomonas alcaligenes MTCC 5264 having the capability to degrade caffeine were immobilized on a cellophane membrane with a molecular weight cut off (MWCO) of 3000–6000 by covalent crosslinking method using glutaraledhyde as the bifunctional crosslinking agent and gelatin as the protein based stabilizing agent (PBSA). The biosensor system was able to detect caffeine in solution over a concentration range of 0.1 to 1mgmL−1. With read-times as short as 3min, this caffeine biosensor acts as a rapid analysis system for caffeine in solutions. Interestingly, successful isolation and immobilization of caffeine degrading bacteria for the analysis of caffeine described here was enabled by a novel selection strategy that incorporated isolation of caffeine degrading bacteria capable of utilizing caffeine as the sole source of carbon and nitrogen from soils and induction of caffeine degrading capacity in bacteria for the development of the biosensor. This biosensor is highly specific for caffeine and response to interfering compounds such as theophylline, theobromine, paraxanthine, other methyl xanthines and sugars was found to be negligible.Although a few biosensing methods for caffeine are reported, they have limitations in application for commercial samples. The development and application of new caffeine detection methods remains an active area of investigation, particularly in food and clinical chemistry. The optimum pH and temperature of measurement were 6.8 and 30±2°C, respectively. Interference in analysis of caffeine due to different substrates was observed but was not considerable. Caffeine content of commercial samples of instant tea and coffee was analyzed by the biosensor and the results compared well with HPLC analysis.
Keywords: Caffeine; Biosensor; Amperometric; Immobilization; Microbial biosensor; High-performance liquid chromatography
Development of a biosensor for caffeine by V.R. Sarath Babu; S. Patra; N.G. Karanth; M.A. Kumar; M.S. Thakur (pp. 329-334).
We have utilized a microbe, which can degrade caffeine to develop an Amperometric biosensor for determination of caffeine in solutions. Whole cells of Pseudomonas alcaligenes MTCC 5264 having the capability to degrade caffeine were immobilized on a cellophane membrane with a molecular weight cut off (MWCO) of 3000–6000 by covalent crosslinking method using glutaraledhyde as the bifunctional crosslinking agent and gelatin as the protein based stabilizing agent (PBSA). The biosensor system was able to detect caffeine in solution over a concentration range of 0.1 to 1mgmL−1. With read-times as short as 3min, this caffeine biosensor acts as a rapid analysis system for caffeine in solutions. Interestingly, successful isolation and immobilization of caffeine degrading bacteria for the analysis of caffeine described here was enabled by a novel selection strategy that incorporated isolation of caffeine degrading bacteria capable of utilizing caffeine as the sole source of carbon and nitrogen from soils and induction of caffeine degrading capacity in bacteria for the development of the biosensor. This biosensor is highly specific for caffeine and response to interfering compounds such as theophylline, theobromine, paraxanthine, other methyl xanthines and sugars was found to be negligible.Although a few biosensing methods for caffeine are reported, they have limitations in application for commercial samples. The development and application of new caffeine detection methods remains an active area of investigation, particularly in food and clinical chemistry. The optimum pH and temperature of measurement were 6.8 and 30±2°C, respectively. Interference in analysis of caffeine due to different substrates was observed but was not considerable. Caffeine content of commercial samples of instant tea and coffee was analyzed by the biosensor and the results compared well with HPLC analysis.
Keywords: Caffeine; Biosensor; Amperometric; Immobilization; Microbial biosensor; High-performance liquid chromatography
Immobilization of cholesterol esterase and cholesterol oxidase onto sol–gel films for application to cholesterol biosensor by Suman Singh; Rahul Singhal; B.D. Malhotra (pp. 335-343).
Cholesterol oxidase (ChOx) and cholesterol esterase (ChEt) have been covalently immobilized onto tetraethylorthosilicate (TEOS) sol–gel films. The tetraethylorthosilicate sol–gel/ChEt/ChOx enzyme films thus prepared have been characterized using scanning electron microscopic (SEM), UV–vis spectroscopic, Fourier-transform-infrared (FTIR) spectroscopic and amperometric techniques, respectively. The results of photometric measurements carried out on tetraethylorthosilicate sol–gel/ChEt/ChOx reveal thermal stability up to 55°C, response time as 180s, linearity up to 780mgdL−1 (12mM), shelf life of 1 month, detection limit of 12mgdL−1 and sensitivity as 5.4×10−5Abs.mg−1dL−1.
Keywords: Tetraethylorthosilicate (TEOS) sol–gel; Cholesterol oxidase; Cholesterol esterase; Cholesterol oleate; Encapsulation; Cholesterol biosensor
Immobilization of cholesterol esterase and cholesterol oxidase onto sol–gel films for application to cholesterol biosensor by Suman Singh; Rahul Singhal; B.D. Malhotra (pp. 335-343).
Cholesterol oxidase (ChOx) and cholesterol esterase (ChEt) have been covalently immobilized onto tetraethylorthosilicate (TEOS) sol–gel films. The tetraethylorthosilicate sol–gel/ChEt/ChOx enzyme films thus prepared have been characterized using scanning electron microscopic (SEM), UV–vis spectroscopic, Fourier-transform-infrared (FTIR) spectroscopic and amperometric techniques, respectively. The results of photometric measurements carried out on tetraethylorthosilicate sol–gel/ChEt/ChOx reveal thermal stability up to 55°C, response time as 180s, linearity up to 780mgdL−1 (12mM), shelf life of 1 month, detection limit of 12mgdL−1 and sensitivity as 5.4×10−5Abs.mg−1dL−1.
Keywords: Tetraethylorthosilicate (TEOS) sol–gel; Cholesterol oxidase; Cholesterol esterase; Cholesterol oleate; Encapsulation; Cholesterol biosensor
Brdička-type processes of cysteine and cysteine-containing peptides on silver amalgam electrodes by Renáta Šelešovská-Fadrná; Miroslav Fojta; Tomáš Navrátil; Jaromíra Chýlková (pp. 344-352).
Silver solid amalgam electrode (AgSAE) was used for differential pulse voltammetric (DPV) measurements of cysteine and cysteine-containing peptides, glutathione, γ-Glu-Cys-Gly and phytochelatin (γ-Glu-Cys)3-Gly (PC3), in the presence of Co(II) ions. It had been established earlier that cysteine-containing peptides and proteins catalyze hydrogen evolution at mercury electrodes in presence of cobalt salts; these processes are known as the Brdička reaction. DPV signals measured with the AgSAE, the surfaces of which had been modified by mercury meniscus or mercury film, were qualitatively the same as those obtained with the hanging mercury drop electrode (HMDE). With these electrodes the number and the intensity of Brdička signals of cysteine, glutathione and PC3 differed, making a distinction among them possible. On the other hand, with the polished silver solid amalgam electrode (the surface of which was completely free of liquid mercury) all three compounds produced only one but strikingly intense peak in the region of Brdička reaction. Using this signal, cysteine, glutathione as well as PC3 could be determined at 10−8M level, representing sensitivity up to 2 orders of magnitude better than attained with the mercury-modified AgSAEs or HMDE.
Keywords: Silver solid amalgam electrode; Hanging mercury drop electrode; Brdička reaction; Catalytic hydrogen evolution; Cysteine; Glutathione; Phytochelatin
Brdička-type processes of cysteine and cysteine-containing peptides on silver amalgam electrodes by Renáta Šelešovská-Fadrná; Miroslav Fojta; Tomáš Navrátil; Jaromíra Chýlková (pp. 344-352).
Silver solid amalgam electrode (AgSAE) was used for differential pulse voltammetric (DPV) measurements of cysteine and cysteine-containing peptides, glutathione, γ-Glu-Cys-Gly and phytochelatin (γ-Glu-Cys)3-Gly (PC3), in the presence of Co(II) ions. It had been established earlier that cysteine-containing peptides and proteins catalyze hydrogen evolution at mercury electrodes in presence of cobalt salts; these processes are known as the Brdička reaction. DPV signals measured with the AgSAE, the surfaces of which had been modified by mercury meniscus or mercury film, were qualitatively the same as those obtained with the hanging mercury drop electrode (HMDE). With these electrodes the number and the intensity of Brdička signals of cysteine, glutathione and PC3 differed, making a distinction among them possible. On the other hand, with the polished silver solid amalgam electrode (the surface of which was completely free of liquid mercury) all three compounds produced only one but strikingly intense peak in the region of Brdička reaction. Using this signal, cysteine, glutathione as well as PC3 could be determined at 10−8M level, representing sensitivity up to 2 orders of magnitude better than attained with the mercury-modified AgSAEs or HMDE.
Keywords: Silver solid amalgam electrode; Hanging mercury drop electrode; Brdička reaction; Catalytic hydrogen evolution; Cysteine; Glutathione; Phytochelatin
Blank problems in trace analysis of diethylhexyl and dibutyl phthalate: Investigation of the sources, tips and tricks by Anja Fankhauser-Noti; Koni Grob (pp. 353-360).
The analysis of phthalates, particularly that of di(2-ethylhexyl)phthalate (DEHP) and dibutyl phthalate (DBP), is notorious for blank problems. Methods and tools are listed to identify the sources and reduce the system contamination to below 1pg DEHP and DBP or below 1ngmL−1 of sample solution. Once direct contact with phthalate-containing plastic articles is ruled out, the air is the major source, primarily via absorption to the surfaces of laboratory glass ware. A main improvement was achieved by cleaning solvents with aluminium oxide permanently left in the reservoirs. The data enables to estimate the contamination to be expected and to design methods keeping blanks below a critical threshold.
Keywords: Phthalates; Di(2-ethylhexyl)phthalate; Dibutyl phthalate; Blank problem; Absorption from the air; Aluminium oxide for cleaning solvent
Blank problems in trace analysis of diethylhexyl and dibutyl phthalate: Investigation of the sources, tips and tricks by Anja Fankhauser-Noti; Koni Grob (pp. 353-360).
The analysis of phthalates, particularly that of di(2-ethylhexyl)phthalate (DEHP) and dibutyl phthalate (DBP), is notorious for blank problems. Methods and tools are listed to identify the sources and reduce the system contamination to below 1pg DEHP and DBP or below 1ngmL−1 of sample solution. Once direct contact with phthalate-containing plastic articles is ruled out, the air is the major source, primarily via absorption to the surfaces of laboratory glass ware. A main improvement was achieved by cleaning solvents with aluminium oxide permanently left in the reservoirs. The data enables to estimate the contamination to be expected and to design methods keeping blanks below a critical threshold.
Keywords: Phthalates; Di(2-ethylhexyl)phthalate; Dibutyl phthalate; Blank problem; Absorption from the air; Aluminium oxide for cleaning solvent
Hydrogen peroxide biosensor based on hemoglobin modified zirconia nanoparticles-grafted collagen matrix by Shuizhen Zong; Yong Cao; Yuming Zhou; Huangxian Ju (pp. 361-366).
A novel method for the immobilization of hemoglobin (Hb) and preparation of reagentless biosensor was proposed using a biocompatible non-toxic zirconia enhanced grafted collagen tri-helix scaffold. The formed membrane was characterized with UV–vis and FT-IR spectroscopy, scanning electron microscope and electrochemical methods. The Hb immobilized in the matrix showed excellent direct electrochemistry with an electron transfer rate constant of 6.46s−1 and electrocatalytic activity to the reduction of hydrogen peroxide. The apparent Michaelis–Menten constant for H2O2 was 0.026mM, showing good affinity. Based on the direct electrochemistry, a new biosensor for H2O2 ranging from 0.8 to 132μM was constructed. Owing to the porous structure and high enzyme loading of the matrix the biosensor exhibited low limit of detection of 0.12μM at 3 σ, fast response less than 5s and high sensitivity of 45.6mAM−1cm−2. The biosensor exhibited acceptable stability and reproducibility. ZrO2-grafted collagen provided a good matrix for protein immobilization and biosensing preparation. This method was useful for monitoring H2O2 in practical samples with the satisfactory results.
Keywords: Biosensor; Direct electrochemistry; Grafted collagen; Zirconia nanoparticles; Hemoglobin; Hydrogen peroxide
Hydrogen peroxide biosensor based on hemoglobin modified zirconia nanoparticles-grafted collagen matrix by Shuizhen Zong; Yong Cao; Yuming Zhou; Huangxian Ju (pp. 361-366).
A novel method for the immobilization of hemoglobin (Hb) and preparation of reagentless biosensor was proposed using a biocompatible non-toxic zirconia enhanced grafted collagen tri-helix scaffold. The formed membrane was characterized with UV–vis and FT-IR spectroscopy, scanning electron microscope and electrochemical methods. The Hb immobilized in the matrix showed excellent direct electrochemistry with an electron transfer rate constant of 6.46s−1 and electrocatalytic activity to the reduction of hydrogen peroxide. The apparent Michaelis–Menten constant for H2O2 was 0.026mM, showing good affinity. Based on the direct electrochemistry, a new biosensor for H2O2 ranging from 0.8 to 132μM was constructed. Owing to the porous structure and high enzyme loading of the matrix the biosensor exhibited low limit of detection of 0.12μM at 3 σ, fast response less than 5s and high sensitivity of 45.6mAM−1cm−2. The biosensor exhibited acceptable stability and reproducibility. ZrO2-grafted collagen provided a good matrix for protein immobilization and biosensing preparation. This method was useful for monitoring H2O2 in practical samples with the satisfactory results.
Keywords: Biosensor; Direct electrochemistry; Grafted collagen; Zirconia nanoparticles; Hemoglobin; Hydrogen peroxide
Kinetic determination of morphine by means of Bray–Liebhafsky oscillatory reaction system using analyte pulse perturbation technique by Nataša D. Pejić; Slavica M. Blagojević; Slobodan R. Anić; Vladana B. Vukojević; Miroslav D. Mijatović; Jasna S. Ćirić; Zoran S. Marković; Svetlana D. Marković; Ljiljana Z. Kolar-Anić (pp. 367-374).
A novel kinetic method for micro-quantitative determinations of morphine (MH) is proposed and validated. The method is based on the potentiometric monitoring of the concentration perturbations of the oscillatory reaction system being in a stable non-equilibrium stationary state close to the bifurcation point between stable and oscillatory state. The response of the Bray–Liebhafsky (BL) oscillatory reaction as a matrix system, to the perturbations by different concentrations of morphine, is followed by a Pt-electrode. The proposed method relies on the linear relationship between maximal potential shift, Δ Em, and the logarithm of the added morphine amounts in the range of 0.004–0.18μmol. Under optimum conditions, the sensitivity of the proposed method (as the limit of detection) is 0.001μmol and the method is featured by good precision (R.S.D.=1.6%) as well as the excellent sample throughput (45samplesh−1). In addition to standard solution analysis, this approach was successfully applied for quantitative determination of morphine in a typical pharmaceutical dosage form. Some aspects of the possible mechanism of morphine action on the BL oscillating chemical system are discussed in detail.
Keywords: Morphine; Bray–Liebhafsky reaction; Quantitative analysis; Analyte pulse perturbation; Kinetic method
Kinetic determination of morphine by means of Bray–Liebhafsky oscillatory reaction system using analyte pulse perturbation technique by Nataša D. Pejić; Slavica M. Blagojević; Slobodan R. Anić; Vladana B. Vukojević; Miroslav D. Mijatović; Jasna S. Ćirić; Zoran S. Marković; Svetlana D. Marković; Ljiljana Z. Kolar-Anić (pp. 367-374).
A novel kinetic method for micro-quantitative determinations of morphine (MH) is proposed and validated. The method is based on the potentiometric monitoring of the concentration perturbations of the oscillatory reaction system being in a stable non-equilibrium stationary state close to the bifurcation point between stable and oscillatory state. The response of the Bray–Liebhafsky (BL) oscillatory reaction as a matrix system, to the perturbations by different concentrations of morphine, is followed by a Pt-electrode. The proposed method relies on the linear relationship between maximal potential shift, Δ Em, and the logarithm of the added morphine amounts in the range of 0.004–0.18μmol. Under optimum conditions, the sensitivity of the proposed method (as the limit of detection) is 0.001μmol and the method is featured by good precision (R.S.D.=1.6%) as well as the excellent sample throughput (45samplesh−1). In addition to standard solution analysis, this approach was successfully applied for quantitative determination of morphine in a typical pharmaceutical dosage form. Some aspects of the possible mechanism of morphine action on the BL oscillating chemical system are discussed in detail.
Keywords: Morphine; Bray–Liebhafsky reaction; Quantitative analysis; Analyte pulse perturbation; Kinetic method
Stable carbon (12/13C) and nitrogen (14/15N) isotopes as a tool for identifying the sources of cyanide in wastes and contaminated soils—A method development by Jenny Weihmann; Tim Mansfeldt; Ulrike Schulte (pp. 375-381).
The occurrence of iron–cyanide complexes in the environment is of concern, since they are potentially hazardous. In order to determine the source of iron–cyanide complexes in contaminated soils and wastes, we developed a method based on the stable isotope ratios13C/12C and15N/14N of the complexed cyanide-ion (CN−). The method was tested on three pure chemicals and two industrials wastes: blast-furnace sludge (BFS) and gas-purifier waste (GPW). The iron–cyanide complexes were converted into the solid cupric ferrocyanide, Cu2[Fe(CN)6]·7H2O, followed by combustion and determination of the isotope-ratios by continuous flow isotope ratio mass spectrometry. Cupric ferrocyanide was obtained from the materials by (i) an alkaline extraction with 1M NaOH and (ii) a distillate digestion. The [Fe(CN)6]4− of the alkaline extraction was precipitated after adding Cu2+. The CN− of the distillate digestion was at first complexed with Fe2+ under inert conditions and then precipitated after adding Cu2+. The δ13C-values obtained by the two methods differed slightly up to 1–3‰ for standards and BFS. The difference was larger for alkaline-extracted GPW (4–7‰), since non-cyanide C was co-extracted and co-precipitated. Therefore the distillate digestion technique is recommended when determining the C isotope ratios in samples rich in organic carbon. Since the δ13C-values of BFS are in the range of −30 to −24‰ and of −17 to −5‰ for GPW, carbon seems to be a suitable tracer for identifying the source of cyanide in both wastes. However, the δ15N-values overlapped for BFS and GPW, making nitrogen unsuitable as a tracer.
Keywords: Stable isotopes; Carbon; Nitrogen; Cyanide; Waste; Soil
Stable carbon (12/13C) and nitrogen (14/15N) isotopes as a tool for identifying the sources of cyanide in wastes and contaminated soils—A method development by Jenny Weihmann; Tim Mansfeldt; Ulrike Schulte (pp. 375-381).
The occurrence of iron–cyanide complexes in the environment is of concern, since they are potentially hazardous. In order to determine the source of iron–cyanide complexes in contaminated soils and wastes, we developed a method based on the stable isotope ratios13C/12C and15N/14N of the complexed cyanide-ion (CN−). The method was tested on three pure chemicals and two industrials wastes: blast-furnace sludge (BFS) and gas-purifier waste (GPW). The iron–cyanide complexes were converted into the solid cupric ferrocyanide, Cu2[Fe(CN)6]·7H2O, followed by combustion and determination of the isotope-ratios by continuous flow isotope ratio mass spectrometry. Cupric ferrocyanide was obtained from the materials by (i) an alkaline extraction with 1M NaOH and (ii) a distillate digestion. The [Fe(CN)6]4− of the alkaline extraction was precipitated after adding Cu2+. The CN− of the distillate digestion was at first complexed with Fe2+ under inert conditions and then precipitated after adding Cu2+. The δ13C-values obtained by the two methods differed slightly up to 1–3‰ for standards and BFS. The difference was larger for alkaline-extracted GPW (4–7‰), since non-cyanide C was co-extracted and co-precipitated. Therefore the distillate digestion technique is recommended when determining the C isotope ratios in samples rich in organic carbon. Since the δ13C-values of BFS are in the range of −30 to −24‰ and of −17 to −5‰ for GPW, carbon seems to be a suitable tracer for identifying the source of cyanide in both wastes. However, the δ15N-values overlapped for BFS and GPW, making nitrogen unsuitable as a tracer.
Keywords: Stable isotopes; Carbon; Nitrogen; Cyanide; Waste; Soil
Nondestructive and rapid determination of nitrate in soil, dry deposits and aerosol samples using KBr-matrix with diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) by Santosh Kumar Verma; Manas Kanti Deb (pp. 382-389).
This paper presents the development of a new, rapid and precise analytical method for submicrogram levels of nitrate (NO3−) in environmental samples like soil, dry deposit samples, and coarse and fine aerosol particles. The determination of submicrogram levels of nitrate is based on the selection of a quantitative analytical peak at 1385cm−1 among the three observed vibrational peaks and preparing calibration curves using different known concentrations of nitrate by diffuse reflectance Fourier transform infra red spectrometric (DRIFTS) technique. Pre-weighed and ground infrared (IR) grade KBr was used as substrate over which remarkably wide range of known concentration of nitrate was sprayed and dried. The dried sample was analyzed by DRIFTS and absorbance was measured. Eight calibration curves for four different concentration ranges of nitrate for absorbance as well as peak area were prepared for samples containing lower and relatively higher values of nitrate. The relative standard deviation ( n=8) for the nitrate concentration ranges, 0.05–40, 0.05–1.5, 1.5–25, 5–40μg/0.1gKBr were in the range 1.6–2.3% for the above calibration curves. The limit of detection (LOD) of the method is 0.07μgg−1 NO3−. The F- and t-tests were performed to check the analytical quality assurance test. The noteworthy feature of the reported method is the noninterference of any of the associated cations. The results were compared with that of ion-chromatographic method with high degree of acceptability. The method can be applied in wide concentration ranges. The method is reagent less, nondestructive, very fast, repeatable, and accurate and has high sample throughput value.
Keywords: Infrared spectroscopy; Diffuse reflectance; Quantitative nitrate determination; Environmental samples
Nondestructive and rapid determination of nitrate in soil, dry deposits and aerosol samples using KBr-matrix with diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) by Santosh Kumar Verma; Manas Kanti Deb (pp. 382-389).
This paper presents the development of a new, rapid and precise analytical method for submicrogram levels of nitrate (NO3−) in environmental samples like soil, dry deposit samples, and coarse and fine aerosol particles. The determination of submicrogram levels of nitrate is based on the selection of a quantitative analytical peak at 1385cm−1 among the three observed vibrational peaks and preparing calibration curves using different known concentrations of nitrate by diffuse reflectance Fourier transform infra red spectrometric (DRIFTS) technique. Pre-weighed and ground infrared (IR) grade KBr was used as substrate over which remarkably wide range of known concentration of nitrate was sprayed and dried. The dried sample was analyzed by DRIFTS and absorbance was measured. Eight calibration curves for four different concentration ranges of nitrate for absorbance as well as peak area were prepared for samples containing lower and relatively higher values of nitrate. The relative standard deviation ( n=8) for the nitrate concentration ranges, 0.05–40, 0.05–1.5, 1.5–25, 5–40μg/0.1gKBr were in the range 1.6–2.3% for the above calibration curves. The limit of detection (LOD) of the method is 0.07μgg−1 NO3−. The F- and t-tests were performed to check the analytical quality assurance test. The noteworthy feature of the reported method is the noninterference of any of the associated cations. The results were compared with that of ion-chromatographic method with high degree of acceptability. The method can be applied in wide concentration ranges. The method is reagent less, nondestructive, very fast, repeatable, and accurate and has high sample throughput value.
Keywords: Infrared spectroscopy; Diffuse reflectance; Quantitative nitrate determination; Environmental samples
Chemometric application in classification and assessment of monitoring locations of an urban river system by Prakash Raj Kannel; Seockheon Lee; Sushil Raj Kanel; Siddhi Pratap Khan (pp. 390-399).
The study presents the application of selected chemometric techniques: cluster analysis, principal component analysis, factor analysis and discriminant analysis, to classify a river water quality and evaluation of the pollution data. Seventeen stations, monitored for 16 physical and chemical parameters in 4 seasons during the period 1999–2003, located at the Bagmati river basin in Kathmandu Valley, Nepal were selected for the purpose of this study. The results allowed, determining natural clusters of monitoring stations with similar pollution characteristics and identifying main discriminant variables that are important for regional water quality variation and possible pollution sources affecting the river water quality. The analysis enabled to group 17 monitoring sites into 3 regions with 5 major discriminating variables: EC, DO, CL, NO2N and BOD. Results revealed that some locations were under the high influence of municipal contamination and some others under the influence of minerals. This study demonstrated that chemometric method is effective for river water classification, and for rapid assessment of water qualities, using the representative sites; it could serve to optimize cost and time without losing any significance of the outcome.
Keywords: Water quality; Classification; Bagmati River; Chemometrics
Chemometric application in classification and assessment of monitoring locations of an urban river system by Prakash Raj Kannel; Seockheon Lee; Sushil Raj Kanel; Siddhi Pratap Khan (pp. 390-399).
The study presents the application of selected chemometric techniques: cluster analysis, principal component analysis, factor analysis and discriminant analysis, to classify a river water quality and evaluation of the pollution data. Seventeen stations, monitored for 16 physical and chemical parameters in 4 seasons during the period 1999–2003, located at the Bagmati river basin in Kathmandu Valley, Nepal were selected for the purpose of this study. The results allowed, determining natural clusters of monitoring stations with similar pollution characteristics and identifying main discriminant variables that are important for regional water quality variation and possible pollution sources affecting the river water quality. The analysis enabled to group 17 monitoring sites into 3 regions with 5 major discriminating variables: EC, DO, CL, NO2N and BOD. Results revealed that some locations were under the high influence of municipal contamination and some others under the influence of minerals. This study demonstrated that chemometric method is effective for river water classification, and for rapid assessment of water qualities, using the representative sites; it could serve to optimize cost and time without losing any significance of the outcome.
Keywords: Water quality; Classification; Bagmati River; Chemometrics