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Analytical and Bioanalytical Chemistry (v.383, #5)
Technical Systems for Biotechnology and Environment: 12th Heiligenstädter Colloquium, 27–29 October 2004, Heiligenstadt, Germany
by Dieter Beckmann (pp. 731-732).
Technical Systems for Biotechnology and Environment: 12th Heiligenstädter Colloquium, 27–29 October 2004, Heiligenstadt, Germany
by Dieter Beckmann (pp. 731-732).
A capillary electrophoresis chip with hydrodynamic sample injection for measurements from a continuous sample flow by S. Büttgenbach; R. Wilke (pp. 733-737).
A microchip-based capillary electrophoresis device supported by a microfluidic network made of poly(dimethylsiloxane), used for measuring target analytes from a continuous sample flow, is presented. The microsystem was fabricated by means of replica molding in combination with standard microfabrication technologies, resulting in microfluidic components and an electrochemical detector. A new hydrodynamic sample injection procedure is introduced, and the maximum number of consecutive measurements that can be made with a poly(dimethylsiloxane) capillary electrophoresis chip with amperometric detection is investigated with respect to reproducibility. The device features a high degree of functional integration, so the benefits associated with miniaturized analysis systems apply to it.
Keywords: Microchip capillary electrophoresis; On-line monitoring; Poly(dimethylsiloxane); Hydrodynamic sample injection
A capillary electrophoresis chip with hydrodynamic sample injection for measurements from a continuous sample flow by S. Büttgenbach; R. Wilke (pp. 733-737).
A microchip-based capillary electrophoresis device supported by a microfluidic network made of poly(dimethylsiloxane), used for measuring target analytes from a continuous sample flow, is presented. The microsystem was fabricated by means of replica molding in combination with standard microfabrication technologies, resulting in microfluidic components and an electrochemical detector. A new hydrodynamic sample injection procedure is introduced, and the maximum number of consecutive measurements that can be made with a poly(dimethylsiloxane) capillary electrophoresis chip with amperometric detection is investigated with respect to reproducibility. The device features a high degree of functional integration, so the benefits associated with miniaturized analysis systems apply to it.
Keywords: Microchip capillary electrophoresis; On-line monitoring; Poly(dimethylsiloxane); Hydrodynamic sample injection
Microstructured layers of spherical biofunctional core-shell nanoparticles provide enlarged reactive surfaces for protein microarrays by Kirsten Borchers; Achim Weber; Herwig Brunner; Günter E. M. Tovar (pp. 738-746).
Nanostructured core-shell particles with tailor-made affinity surfaces were used to generate microstructured affinity surfaces by microspotting the particles to form densely packed amorphous nanoparticle layers. These layers provided a large reactive surface for the specific binding of protein ligands from aqueous solution. Biofunctional core-shell particles were synthesized for this purpose that consisted of a silica core with a diameter of 100 nm and an organic shell a few nm thick. The nanoparticle core was prepared by sol-gel chemistry and the shell formed in suspension by organosilane chemistry. The shell provided amino groups or carbonyl groups at its outer surface for subsequent covalent immobilization of streptavidin, rabbit IgG antibodies or goat IgG antibodies. AlexaFluor 647®-conjugated and biotinylated cytochrome C and CyDye-labeled anti-rabbit IgG and anti-goat IgG were probed as model analytes. The core-shell nanoparticles were spotted using a pin-ring micro-arrayer onto microscope glass slides that were coated with a polycation monolayer by dip-coating prior to nanoparticle deposition. Amorphous particle layers of well-defined thicknesses in the range of 100 nm to 2 μm were obtained by printing aqueous particle suspensions containing 5–500 mg/mL (0.5–50 wt%) of silica particles. The specific affinity of the plotted nanoparticulate capture surface was demonstrated by binding Cy3-labeled donkey anti-rabbit IgG and Cy5-labeled mouse anti-goat IgG to immobilized rabbit IgG and goat IgG particles. The signal intensity per spot increased for any given analyte concentration when the amount of particles per spot was augmented. This was attributed to the increasing integration of receptor molecules per surface footprint, which shifted the binding equilibrium towards the formation of the receptor–ligand complex. Additionally, the locally-increased supply of receptor molecules at the nanoparticulate microchip surface resulted in a wide dynamic range of 4 fM–20 nM (covering six orders of magnitude).
Keywords: Fluorescence label; Capturing; Protein biochip; Bioconjugation; Dynamic range
Microstructured layers of spherical biofunctional core-shell nanoparticles provide enlarged reactive surfaces for protein microarrays by Kirsten Borchers; Achim Weber; Herwig Brunner; Günter E. M. Tovar (pp. 738-746).
Nanostructured core-shell particles with tailor-made affinity surfaces were used to generate microstructured affinity surfaces by microspotting the particles to form densely packed amorphous nanoparticle layers. These layers provided a large reactive surface for the specific binding of protein ligands from aqueous solution. Biofunctional core-shell particles were synthesized for this purpose that consisted of a silica core with a diameter of 100 nm and an organic shell a few nm thick. The nanoparticle core was prepared by sol-gel chemistry and the shell formed in suspension by organosilane chemistry. The shell provided amino groups or carbonyl groups at its outer surface for subsequent covalent immobilization of streptavidin, rabbit IgG antibodies or goat IgG antibodies. AlexaFluor 647®-conjugated and biotinylated cytochrome C and CyDye-labeled anti-rabbit IgG and anti-goat IgG were probed as model analytes. The core-shell nanoparticles were spotted using a pin-ring micro-arrayer onto microscope glass slides that were coated with a polycation monolayer by dip-coating prior to nanoparticle deposition. Amorphous particle layers of well-defined thicknesses in the range of 100 nm to 2 μm were obtained by printing aqueous particle suspensions containing 5–500 mg/mL (0.5–50 wt%) of silica particles. The specific affinity of the plotted nanoparticulate capture surface was demonstrated by binding Cy3-labeled donkey anti-rabbit IgG and Cy5-labeled mouse anti-goat IgG to immobilized rabbit IgG and goat IgG particles. The signal intensity per spot increased for any given analyte concentration when the amount of particles per spot was augmented. This was attributed to the increasing integration of receptor molecules per surface footprint, which shifted the binding equilibrium towards the formation of the receptor–ligand complex. Additionally, the locally-increased supply of receptor molecules at the nanoparticulate microchip surface resulted in a wide dynamic range of 4 fM–20 nM (covering six orders of magnitude).
Keywords: Fluorescence label; Capturing; Protein biochip; Bioconjugation; Dynamic range
Performance of calorimetric methods for the investigation of microbial systems in combination with additional sensors by F. Ullrich; M. Winkelmann; R. Hüttl; G. Wolf (pp. 747-751).
Calorimetric methods are used in combination with online oxygen measurement (using an amperometric sensor) and determination of the optical density (using a fibre optic sensor) to investigate microbial growth behaviour. The calorimetric curves of different batch experiments show a characteristic and reproducible course. Changes in the slope of the ΔT–time curves indicate the effects of limiting factors on the microbial activity during the cultivation. A first limitation could be correlated with the depletion of oxygen in the medium; a second correlates with the depletion of the carbon source. Measurements of optical density in some cases provide reliable information about the growth of a microorganism culture. Our measurements show a good correlation of the universal calorimetric signal (heat–time curve) to the signal of the miniaturised photometric (OD) sensor.
Keywords: Calorimetry; Microbial; Substrate limitation; Fibre optic sensor; Oxygen sensor
Performance of calorimetric methods for the investigation of microbial systems in combination with additional sensors by F. Ullrich; M. Winkelmann; R. Hüttl; G. Wolf (pp. 747-751).
Calorimetric methods are used in combination with online oxygen measurement (using an amperometric sensor) and determination of the optical density (using a fibre optic sensor) to investigate microbial growth behaviour. The calorimetric curves of different batch experiments show a characteristic and reproducible course. Changes in the slope of the ΔT–time curves indicate the effects of limiting factors on the microbial activity during the cultivation. A first limitation could be correlated with the depletion of oxygen in the medium; a second correlates with the depletion of the carbon source. Measurements of optical density in some cases provide reliable information about the growth of a microorganism culture. Our measurements show a good correlation of the universal calorimetric signal (heat–time curve) to the signal of the miniaturised photometric (OD) sensor.
Keywords: Calorimetry; Microbial; Substrate limitation; Fibre optic sensor; Oxygen sensor
New type of dry substances content meter using microwaves for application in biogas plants by Thomas Nacke; Kathleen Brückner; Arndt Göller; Sebastian Kaufhold; Xenia Nakos; Stephan Noack; Heinrich Stöber; Dieter Beckmann (pp. 752-757).
Dry substances (DS) are an important index for monitoring and controlling anaerobic co-digestion in biogas plants. We have developed and tested an online meter that measures suspended solids by means of the reflection coefficient of an exiting microwave signal, which is dependent on the dielectric properties of the suspensions. Intelligent models based on partial least squares regression (PLSR) and artificial neural network (ANN) for calibration allow exact and reproducible measurements under different circumstances. This measuring method is appropriate for contactless and online measurements of dry substance contents in biogas plants in a large range from 2–14%.
Keywords: Dry substance; Online measurement; Microwave sensor
New type of dry substances content meter using microwaves for application in biogas plants by Thomas Nacke; Kathleen Brückner; Arndt Göller; Sebastian Kaufhold; Xenia Nakos; Stephan Noack; Heinrich Stöber; Dieter Beckmann (pp. 752-757).
Dry substances (DS) are an important index for monitoring and controlling anaerobic co-digestion in biogas plants. We have developed and tested an online meter that measures suspended solids by means of the reflection coefficient of an exiting microwave signal, which is dependent on the dielectric properties of the suspensions. Intelligent models based on partial least squares regression (PLSR) and artificial neural network (ANN) for calibration allow exact and reproducible measurements under different circumstances. This measuring method is appropriate for contactless and online measurements of dry substance contents in biogas plants in a large range from 2–14%.
Keywords: Dry substance; Online measurement; Microwave sensor
Comparison between RGD-peptide-modified titanium and borosilicate surfaces by N. Senyah; G. Hildebrand; K. Liefeith (pp. 758-762).
The use of synthetic peptides containing adhesive sequences, such as the Arg-Gly-Asp (RGD) motif, represents a promising strategy to control biological interactions at the cell–material interface. These peptides are known to improve the tissue–material contact owing to highly specific binding to cellular membrane receptors known as integrins, thereby promoting the adhesion, migration and proliferation of cells. The peptides were coupled to borosilicate glass and titanium surfaces using silanisation chemistry. A tryptophan residue was incorporated into the amino acid sequences of selected peptides to facilitate the detection of the covalently bound peptides. Successful peptide immobilisation was proven by fluorimetric measurements. The confocal imaging analysis suggests a homogeneous distribution of the immobilised peptide across the biomaterial surface. In vitro cell proliferation assays were employed to compare the adhesion potentials of the well-known RGD-containing peptides GRGDSP, GRADSP and RGDS to the three peptides designed by our group. The results demonstrate that the RGD sequence is not necessarily required to enhance the adhesion of cells to non-biological surfaces. Moreover, it is shown that the number of adhering cells can be increased by changes in the peptide hydrophobicity. Changes in the cytoskeleton are observed depending on the type of RGD-peptide modification.
Keywords: RGD-peptides; Surface distribution; Cell adhesion; Osteoblasts; Titanium
Comparison between RGD-peptide-modified titanium and borosilicate surfaces by N. Senyah; G. Hildebrand; K. Liefeith (pp. 758-762).
The use of synthetic peptides containing adhesive sequences, such as the Arg-Gly-Asp (RGD) motif, represents a promising strategy to control biological interactions at the cell–material interface. These peptides are known to improve the tissue–material contact owing to highly specific binding to cellular membrane receptors known as integrins, thereby promoting the adhesion, migration and proliferation of cells. The peptides were coupled to borosilicate glass and titanium surfaces using silanisation chemistry. A tryptophan residue was incorporated into the amino acid sequences of selected peptides to facilitate the detection of the covalently bound peptides. Successful peptide immobilisation was proven by fluorimetric measurements. The confocal imaging analysis suggests a homogeneous distribution of the immobilised peptide across the biomaterial surface. In vitro cell proliferation assays were employed to compare the adhesion potentials of the well-known RGD-containing peptides GRGDSP, GRADSP and RGDS to the three peptides designed by our group. The results demonstrate that the RGD sequence is not necessarily required to enhance the adhesion of cells to non-biological surfaces. Moreover, it is shown that the number of adhering cells can be increased by changes in the peptide hydrophobicity. Changes in the cytoskeleton are observed depending on the type of RGD-peptide modification.
Keywords: RGD-peptides; Surface distribution; Cell adhesion; Osteoblasts; Titanium
Surface-enhanced Raman scattering detection of lysophosphatidic acid by Leo Seballos; Jin Z. Zhang; Rebecca Sutphen (pp. 763-767).
Surface-enhanced Raman scattering using silver nanoparticles was applied to detect various forms of lysophosphatidic acid (LPA) to examine its potential application as an alternative to current detection methods of LPA as biomarkers of ovarian cancer. Enhancement of the Raman modes of the molecule, especially those related to the acyl chain within the 800–1300 cm−1 region, was observed. In particular, the C–C vibration mode of the gauche-bonded chain around 1100 cm−1 was enhanced to allow the discrimination of two similar LPA molecules. Given the molecular selectivity of this technique, the detection of LPA using SERS may eliminate the need for partial purification of samples prior to analysis in cancer screening.
Keywords: Surface-enhanced Raman scattering; Lysophosphatidic acid
Surface-enhanced Raman scattering detection of lysophosphatidic acid by Leo Seballos; Jin Z. Zhang; Rebecca Sutphen (pp. 763-767).
Surface-enhanced Raman scattering using silver nanoparticles was applied to detect various forms of lysophosphatidic acid (LPA) to examine its potential application as an alternative to current detection methods of LPA as biomarkers of ovarian cancer. Enhancement of the Raman modes of the molecule, especially those related to the acyl chain within the 800–1300 cm−1 region, was observed. In particular, the C–C vibration mode of the gauche-bonded chain around 1100 cm−1 was enhanced to allow the discrimination of two similar LPA molecules. Given the molecular selectivity of this technique, the detection of LPA using SERS may eliminate the need for partial purification of samples prior to analysis in cancer screening.
Keywords: Surface-enhanced Raman scattering; Lysophosphatidic acid
Evaluation of different strategies for real-time RT-PCR expression analysis of corticotropin-releasing hormone and related proteins in human gestational tissues by Bernd Sehringer; Hans Peter Zahradnik; Wolfgang R. Deppert; Michael Simon; Claudia Noethling; Wolfgang R. Schaefer (pp. 768-775).
In this article real-time quantitative RT-PCR strategies for investigation of mRNA distribution in stress-related corticotropin-releasing hormone (CRH), CRH-binding protein (CRH-BP), and CRH receptors (CRH-R1, CRH-R2) in human gestational tissues are described. The effect of sample and RNA preparation, reverse transcription, and the quantitation strategy were investigated. Both thawing of the sample before homogenization and the RT reaction were identified as critical steps. In contrast, the time-lag from the biopsy until snap-freezing and the homogenization procedure had little effect. The “housekeeping” gene cyclophilin was found to be differently expressed in gestational tissues, compromising its use as internal reference. For relative quantitation of mRNA levels by TaqMan PCR the standard curve method and the comparative C T method (ΔΔC T or ΔC T′ method) were compared. Both calculation strategies delivered similar relative mRNA amounts in identifying the placenta as the main source of CRH and CRH-BP mRNA compared with myometrium and decidua. Consistent results were also obtained for CRH-R1 and CRH-R2 by both methods of calculation. We conclude that the simpler comparative C T method is adequate for assessing the mRNA levels of CRH, CRH-BP, and CRH receptors in human gestational tissues.
Keywords: Real-time PCR; Reverse transcription; Comparative C T method; Standard curve method; Cyclophilin; Corticotropin-releasing hormone
Evaluation of different strategies for real-time RT-PCR expression analysis of corticotropin-releasing hormone and related proteins in human gestational tissues by Bernd Sehringer; Hans Peter Zahradnik; Wolfgang R. Deppert; Michael Simon; Claudia Noethling; Wolfgang R. Schaefer (pp. 768-775).
In this article real-time quantitative RT-PCR strategies for investigation of mRNA distribution in stress-related corticotropin-releasing hormone (CRH), CRH-binding protein (CRH-BP), and CRH receptors (CRH-R1, CRH-R2) in human gestational tissues are described. The effect of sample and RNA preparation, reverse transcription, and the quantitation strategy were investigated. Both thawing of the sample before homogenization and the RT reaction were identified as critical steps. In contrast, the time-lag from the biopsy until snap-freezing and the homogenization procedure had little effect. The “housekeeping” gene cyclophilin was found to be differently expressed in gestational tissues, compromising its use as internal reference. For relative quantitation of mRNA levels by TaqMan PCR the standard curve method and the comparative C T method (ΔΔC T or ΔC T′ method) were compared. Both calculation strategies delivered similar relative mRNA amounts in identifying the placenta as the main source of CRH and CRH-BP mRNA compared with myometrium and decidua. Consistent results were also obtained for CRH-R1 and CRH-R2 by both methods of calculation. We conclude that the simpler comparative C T method is adequate for assessing the mRNA levels of CRH, CRH-BP, and CRH receptors in human gestational tissues.
Keywords: Real-time PCR; Reverse transcription; Comparative C T method; Standard curve method; Cyclophilin; Corticotropin-releasing hormone
Development of a passive micromixer based on repeated fluid twisting and flattening, and its application to DNA purification by Nae Yoon Lee; Masumi Yamada; Minoru Seki (pp. 776-782).
We have developed a three-dimensional passive micromixer based on new mixing principles, fluid twisting and flattening. This micromixer is constructed by repeating two microchannel segments, a “main channel” and a “flattened channel”, which are very different in size and are arranged perpendicularly. At the intersection of these segments the fluid inside the micromixer is twisted and then, in the flattened channel, the diffusion length is greatly reduced, achieving high mixing efficiency. Several types of micromixer were fabricated and the effect of microchannel geometry on mixing performance was evaluated. We also integrated this micromixer with a miniaturized DNA purification device, in which the concentration of the buffer solution could be rapidly changed, to perform DNA purification based on solid-phase extraction.
Keywords: Passive micromixer; Microfluidics; DNA purification; Integration
Development of a passive micromixer based on repeated fluid twisting and flattening, and its application to DNA purification by Nae Yoon Lee; Masumi Yamada; Minoru Seki (pp. 776-782).
We have developed a three-dimensional passive micromixer based on new mixing principles, fluid twisting and flattening. This micromixer is constructed by repeating two microchannel segments, a “main channel” and a “flattened channel”, which are very different in size and are arranged perpendicularly. At the intersection of these segments the fluid inside the micromixer is twisted and then, in the flattened channel, the diffusion length is greatly reduced, achieving high mixing efficiency. Several types of micromixer were fabricated and the effect of microchannel geometry on mixing performance was evaluated. We also integrated this micromixer with a miniaturized DNA purification device, in which the concentration of the buffer solution could be rapidly changed, to perform DNA purification based on solid-phase extraction.
Keywords: Passive micromixer; Microfluidics; DNA purification; Integration
Detection of domoic acid in rat serum and brain by direct competitive enzyme-linked immunosorbent assay (cELISA) by Blair R. Hesp; Joanne C. Harrison; Andrew I. Selwood; Patrick T. Holland; D. Steven Kerr (pp. 783-786).
In 1987 a large-scale incident of human poisoning in Canada was traced to commercial mussels contaminated with domoic acid (DOM). Since then, routine screening of shellfish domoic acid content has been carried out using a variety of assays, with liquid chromatography using ultraviolet absorbance detection (LC–UV) or mass spectrometric detection (LC–MS) being the currently accepted standard methodologies. Recently, a highly specific competitive enzyme-linked immunosorbent assay (cELISA) has been developed for the detection and analysis of DOM in commercial shellfish, but its accuracy relative to LC methods has not been independently verified in mammalian tissues. In this study we demonstrate that measurement of rat serum DOM concentration by cELISA gives a good correlation (r 2=0.993) across a broad range of concentrations when compared to LC–MS analysis, with only a small (15%) overestimation of sample DOM content. In addition, we have developed an extraction method for analysis of DOM in rat brain by cELISA which yields complete recovery across a range of sample dilutions.
Keywords: Domoic acid; Enzyme-linked immunosorbent assay; Liquid chromatography–mass spectrometry; Rat serum; Rat brain
Detection of domoic acid in rat serum and brain by direct competitive enzyme-linked immunosorbent assay (cELISA) by Blair R. Hesp; Joanne C. Harrison; Andrew I. Selwood; Patrick T. Holland; D. Steven Kerr (pp. 783-786).
In 1987 a large-scale incident of human poisoning in Canada was traced to commercial mussels contaminated with domoic acid (DOM). Since then, routine screening of shellfish domoic acid content has been carried out using a variety of assays, with liquid chromatography using ultraviolet absorbance detection (LC–UV) or mass spectrometric detection (LC–MS) being the currently accepted standard methodologies. Recently, a highly specific competitive enzyme-linked immunosorbent assay (cELISA) has been developed for the detection and analysis of DOM in commercial shellfish, but its accuracy relative to LC methods has not been independently verified in mammalian tissues. In this study we demonstrate that measurement of rat serum DOM concentration by cELISA gives a good correlation (r 2=0.993) across a broad range of concentrations when compared to LC–MS analysis, with only a small (15%) overestimation of sample DOM content. In addition, we have developed an extraction method for analysis of DOM in rat brain by cELISA which yields complete recovery across a range of sample dilutions.
Keywords: Domoic acid; Enzyme-linked immunosorbent assay; Liquid chromatography–mass spectrometry; Rat serum; Rat brain
High-performance liquid chromatography–tandem mass spectrometry for identification of isoflavones and description of the biotransformation of kudzu root by Yan Zhang; Qing Xu; Xiaozhe Zhang; Jiping Chen; Xinmiao Liang; Antonius Kettrup (pp. 787-796).
High-performance liquid chromatography–tandem mass spectrometry has been used to identify isoflavone aglycones and glycosides in kudzu root. Fourteen isoflavones were detected. Among these, six were identified by comparison with authentic standards. Tentative identifications of the other isoflavones are based on UV spectra, mass spectra of protonated and deprotonated molecules, and MS–MS data. Several are reported for the first time in kudzu root. The bioactivity and bioavailability of isoflavone aglycones are usually greater than those of their glycosides. To improve the bioavailability of kudzu root isoflavones, crude β-glycosidases prepared from microbes were used to hydrolyze the isoflavone glycosides. Several MS modes are combined not only to identify the isoflavones in kudzu root, but also to describe the biotransformation of kudzu root isoflavone glycosides. It is also proved that crude β-glycosidases have high selectivity toward the O-glycosides of isoflavones.
Keywords: Kudzu root; Isoflavones; LC–MS; Crude β-glycosidase; Biotransformation
High-performance liquid chromatography–tandem mass spectrometry for identification of isoflavones and description of the biotransformation of kudzu root by Yan Zhang; Qing Xu; Xiaozhe Zhang; Jiping Chen; Xinmiao Liang; Antonius Kettrup (pp. 787-796).
High-performance liquid chromatography–tandem mass spectrometry has been used to identify isoflavone aglycones and glycosides in kudzu root. Fourteen isoflavones were detected. Among these, six were identified by comparison with authentic standards. Tentative identifications of the other isoflavones are based on UV spectra, mass spectra of protonated and deprotonated molecules, and MS–MS data. Several are reported for the first time in kudzu root. The bioactivity and bioavailability of isoflavone aglycones are usually greater than those of their glycosides. To improve the bioavailability of kudzu root isoflavones, crude β-glycosidases prepared from microbes were used to hydrolyze the isoflavone glycosides. Several MS modes are combined not only to identify the isoflavones in kudzu root, but also to describe the biotransformation of kudzu root isoflavone glycosides. It is also proved that crude β-glycosidases have high selectivity toward the O-glycosides of isoflavones.
Keywords: Kudzu root; Isoflavones; LC–MS; Crude β-glycosidase; Biotransformation
Multicommuted flow-through fluorescence optosensor for determination of furosemide and triamterene by E. J. Llorent-Martínez; P. Ortega-Barrales; A. Molina-Díaz (pp. 797-803).
Multicommutation implemented with flow-through optosensors is a very promising area of research. This recent approach benefits from the advantages of both methods and results in high sensitivity, selectivity, and speed, and little waste generation. This paper reports the simultaneous determination of furosemide and triamterene, two widely used diuretics, by measurement of their native fluorescence. The system has been proved to be useful for determination of both analytes in pharmaceutical preparations and for determination of triamterene in human urine and serum. A minicolumn filled with Sephadex SPC-25 microbeads was used to achieve separation of both analytes before detection in a flow-through cell filled with the same resin. The sensor is linear in the range 50–1200 and 0.4–8 ng mL−1 with detection limits of 15 and 0.1 ng mL−1 for furosemide and triamterene, respectively.
Keywords: Fluorescence; Multicommutation; Optosensor; Diuretics; Biological fluids
Multicommuted flow-through fluorescence optosensor for determination of furosemide and triamterene by E. J. Llorent-Martínez; P. Ortega-Barrales; A. Molina-Díaz (pp. 797-803).
Multicommutation implemented with flow-through optosensors is a very promising area of research. This recent approach benefits from the advantages of both methods and results in high sensitivity, selectivity, and speed, and little waste generation. This paper reports the simultaneous determination of furosemide and triamterene, two widely used diuretics, by measurement of their native fluorescence. The system has been proved to be useful for determination of both analytes in pharmaceutical preparations and for determination of triamterene in human urine and serum. A minicolumn filled with Sephadex SPC-25 microbeads was used to achieve separation of both analytes before detection in a flow-through cell filled with the same resin. The sensor is linear in the range 50–1200 and 0.4–8 ng mL−1 with detection limits of 15 and 0.1 ng mL−1 for furosemide and triamterene, respectively.
Keywords: Fluorescence; Multicommutation; Optosensor; Diuretics; Biological fluids
Quantification of several monohydroxylated metabolites of polycyclic aromatic hydrocarbons in urine by high-performance liquid chromatography with fluorescence detection by Yu Wang; Wenbing Zhang; Yulian Dong; Ruifang Fan; Guoying Sheng; Jiamo Fu (pp. 804-809).
A high-performance liquid chromatographic method with fluorescence detection has been developed to determine the urinary polycyclic aromatic hydrocarbon metabolites 2-hydroxynaphthalene, 2-hydroxyfluorene, 9-hydroxyphenanthrene, 1-hydroxypyrene and 3-hydroxybenz[a]pyrene. Solid phase extraction (SPE) was used to clean up the samples, and washing with 30% methanol was found to be the best way to remove interferences in the matrix. The method detection limits ranged from 0.044 μg/L for 1-hydroxypyrene to 1.615 μg/L for 3-hydroxybenz[a]pyrene, and the recoveries ranged between 40% for 3-hydroxybenz[a]pyrene and 99% for 2-hydroxynaphthalene. The within-day relative standard deviation was lowest for 2-hydroxynaphthalene at 0.67% and went up to 2.42% for 3-hydroxybenz[a]pyrene, and the between-day relative standard deviation ranged from 3.84% for 9-hydroxyphenanthrene to 10.42% for 2-hydroxyfluorene. The correlation coefficients were between 0.9962 and 0.9998. The developed method was successfully used to analyze samples from student volunteers in a high school.
Keywords: Polycyclic aromatic hydrocarbons; Metabolite; Urine; High-performance liquid chromatography; Solid phase extraction
Quantification of several monohydroxylated metabolites of polycyclic aromatic hydrocarbons in urine by high-performance liquid chromatography with fluorescence detection by Yu Wang; Wenbing Zhang; Yulian Dong; Ruifang Fan; Guoying Sheng; Jiamo Fu (pp. 804-809).
A high-performance liquid chromatographic method with fluorescence detection has been developed to determine the urinary polycyclic aromatic hydrocarbon metabolites 2-hydroxynaphthalene, 2-hydroxyfluorene, 9-hydroxyphenanthrene, 1-hydroxypyrene and 3-hydroxybenz[a]pyrene. Solid phase extraction (SPE) was used to clean up the samples, and washing with 30% methanol was found to be the best way to remove interferences in the matrix. The method detection limits ranged from 0.044 μg/L for 1-hydroxypyrene to 1.615 μg/L for 3-hydroxybenz[a]pyrene, and the recoveries ranged between 40% for 3-hydroxybenz[a]pyrene and 99% for 2-hydroxynaphthalene. The within-day relative standard deviation was lowest for 2-hydroxynaphthalene at 0.67% and went up to 2.42% for 3-hydroxybenz[a]pyrene, and the between-day relative standard deviation ranged from 3.84% for 9-hydroxyphenanthrene to 10.42% for 2-hydroxyfluorene. The correlation coefficients were between 0.9962 and 0.9998. The developed method was successfully used to analyze samples from student volunteers in a high school.
Keywords: Polycyclic aromatic hydrocarbons; Metabolite; Urine; High-performance liquid chromatography; Solid phase extraction
QSAR study on the Ah receptor-binding affinities of polyhalogenated dibenzo-p-dioxins using net atomic-charge descriptors and a radial basis neural network by G. Zheng; M. Xiao; X. H. Lu (pp. 810-816).
A radial basis function neural network (RBFN) has been used to correlate Ah receptor-binding affinities of polychlorinated, polybrominated, and polychlorinated–brominated dibenzo-p-dioxins with molecular weight and eight net atomic charge descriptors. Support vector machine (SVM) and partial least square (PLS) regression models based on the same data set have also been built. Leave-one-out cross-validation was used to train the RBFN, SVM, and PLS models. For predicting Ah receptor-binding affinities, the RBFN model with a squared cross-validation correlation coefficient (q 2) of 0.8818 outperforms the SVM and PLS models and also compares favorably with any other reported quantitative structure–activity relationship model based on the same activity data set. The significance of the RBFN model with net atomic charges as descriptors suggests that electrostatic and dispersion-type interactions play important roles in governing the Ah receptor binding of polychlorinated, polybrominated, and polychlorinated–brominated dibenzo-p-dioxins.
Keywords: PCDDs; QSAR; AhR; RBFN
QSAR study on the Ah receptor-binding affinities of polyhalogenated dibenzo-p-dioxins using net atomic-charge descriptors and a radial basis neural network by G. Zheng; M. Xiao; X. H. Lu (pp. 810-816).
A radial basis function neural network (RBFN) has been used to correlate Ah receptor-binding affinities of polychlorinated, polybrominated, and polychlorinated–brominated dibenzo-p-dioxins with molecular weight and eight net atomic charge descriptors. Support vector machine (SVM) and partial least square (PLS) regression models based on the same data set have also been built. Leave-one-out cross-validation was used to train the RBFN, SVM, and PLS models. For predicting Ah receptor-binding affinities, the RBFN model with a squared cross-validation correlation coefficient (q 2) of 0.8818 outperforms the SVM and PLS models and also compares favorably with any other reported quantitative structure–activity relationship model based on the same activity data set. The significance of the RBFN model with net atomic charges as descriptors suggests that electrostatic and dispersion-type interactions play important roles in governing the Ah receptor binding of polychlorinated, polybrominated, and polychlorinated–brominated dibenzo-p-dioxins.
Keywords: PCDDs; QSAR; AhR; RBFN
Simultaneous determination of rifampicin and isoniazid by continuous-flow chemiluminescence with artificial neural network calibration by Baoxin Li; Yuezhen He; Jiagen Lv; Zhujun Zhang (pp. 817-824).
In this paper a continuous-flow chemiluminescence (CL) system with artificial neural network calibration is proposed for simultaneous determination of rifampicin and isoniazid. This method is based on the different kinetic spectra of the analytes in their CL reaction with alkaline N-bromosuccinimide as oxidant. The CL intensity was measured and recorded every second from 1 to 300 s. The data obtained were processed chemometrically by use of an artificial neural network. The experimental calibration set was 20 sample solutions. The relative standard errors of prediction for both analytes were approximately 5%. The proposed method was successfully applied to the simultaneous determination of rifampicin and isoniazid in a combined pharmaceutical formulation.
Keywords: Chemiluminescence; Artificial neural network; Rifampicin; Isoniazid; Simultaneous determination
Simultaneous determination of rifampicin and isoniazid by continuous-flow chemiluminescence with artificial neural network calibration by Baoxin Li; Yuezhen He; Jiagen Lv; Zhujun Zhang (pp. 817-824).
In this paper a continuous-flow chemiluminescence (CL) system with artificial neural network calibration is proposed for simultaneous determination of rifampicin and isoniazid. This method is based on the different kinetic spectra of the analytes in their CL reaction with alkaline N-bromosuccinimide as oxidant. The CL intensity was measured and recorded every second from 1 to 300 s. The data obtained were processed chemometrically by use of an artificial neural network. The experimental calibration set was 20 sample solutions. The relative standard errors of prediction for both analytes were approximately 5%. The proposed method was successfully applied to the simultaneous determination of rifampicin and isoniazid in a combined pharmaceutical formulation.
Keywords: Chemiluminescence; Artificial neural network; Rifampicin; Isoniazid; Simultaneous determination
Direct determination of selenium in urine samples by electrothermal atomic absorption spectrometry using a Zr plus Rh-treated graphite tube and co-injection of Rh as chemical modifier by Frederico Garcia Pinto; Daniel Andrada; Cristina Gonçalves Magalhães; Berta Rolla Nunes; Flávia Regina de Amorim; Milton Batista Franco; Tatiana Dillenburg Saint'Pierre; José Bento Borba da Silva; Adilson José Curtius (pp. 825-832).
Different chemical modifiers for use with electrothermal atomic absorption spectrometry (ET AAS) were investigated in relation to determining the selenium in human urine samples. The samples were diluted in a solution containing 1% v/v HNO3 and 0.02% m/v cetyltrimethylammonium chloride (CTAC). Studying the modifiers showed that the use of either Ru or Ir as the permanent modifier gave low sensitivity to Se and the peak shape was very noisy, while Zr or Rh gave no peak at all. The same occurred when Zr was used in solution. For mixtures of permanent modifiers, Ir plus Rh or Zr plus Rh gave very low sensitivity, Zr plus Rh with co-injection of Ir in solution was also not efficient, Zr plus Rh in solution gave good sensitivity, but the best results were obtained with a mixture of Zr and Rh as the permanent modifier and co-injection of Rh in solution. Using this last modifier, the following dilutions with the HNO3 and CTAC were studied: 1:1, 1:2, 1:3 and 1:4. The best dilution was 1:1, which promoted good sensitivity and a more defined peak shape and made it possible to correct for the background using a deuterium arc lamp. Under these conditions, a characteristic mass of 26±0.2 pg was obtained for Se in aqueous solution. Six certified urine samples were analyzed using matrix matching calibration and the measured concentrations were in agreement with the certified values, according to a t-test at the 95% confidence level. Recovery tests were carried out and the recoveries were in the range 100–103%, with relative standard deviation better than 9%. The limit of detection (LOD, 3 sd, n=10) was 3.0 μg L−1 in the sample. The treated graphite tube could be used for at least 600 atomization cycles without significant alteration of the analytical signal.
Keywords: Electrothermal atomic absorption spectrometry; Selenium; Human urine; Chemical modifier; Zirconium plus rhodium as permanent modifier
Direct determination of selenium in urine samples by electrothermal atomic absorption spectrometry using a Zr plus Rh-treated graphite tube and co-injection of Rh as chemical modifier by Frederico Garcia Pinto; Daniel Andrada; Cristina Gonçalves Magalhães; Berta Rolla Nunes; Flávia Regina de Amorim; Milton Batista Franco; Tatiana Dillenburg Saint'Pierre; José Bento Borba da Silva; Adilson José Curtius (pp. 825-832).
Different chemical modifiers for use with electrothermal atomic absorption spectrometry (ET AAS) were investigated in relation to determining the selenium in human urine samples. The samples were diluted in a solution containing 1% v/v HNO3 and 0.02% m/v cetyltrimethylammonium chloride (CTAC). Studying the modifiers showed that the use of either Ru or Ir as the permanent modifier gave low sensitivity to Se and the peak shape was very noisy, while Zr or Rh gave no peak at all. The same occurred when Zr was used in solution. For mixtures of permanent modifiers, Ir plus Rh or Zr plus Rh gave very low sensitivity, Zr plus Rh with co-injection of Ir in solution was also not efficient, Zr plus Rh in solution gave good sensitivity, but the best results were obtained with a mixture of Zr and Rh as the permanent modifier and co-injection of Rh in solution. Using this last modifier, the following dilutions with the HNO3 and CTAC were studied: 1:1, 1:2, 1:3 and 1:4. The best dilution was 1:1, which promoted good sensitivity and a more defined peak shape and made it possible to correct for the background using a deuterium arc lamp. Under these conditions, a characteristic mass of 26±0.2 pg was obtained for Se in aqueous solution. Six certified urine samples were analyzed using matrix matching calibration and the measured concentrations were in agreement with the certified values, according to a t-test at the 95% confidence level. Recovery tests were carried out and the recoveries were in the range 100–103%, with relative standard deviation better than 9%. The limit of detection (LOD, 3 sd, n=10) was 3.0 μg L−1 in the sample. The treated graphite tube could be used for at least 600 atomization cycles without significant alteration of the analytical signal.
Keywords: Electrothermal atomic absorption spectrometry; Selenium; Human urine; Chemical modifier; Zirconium plus rhodium as permanent modifier
Determination of magnesium, calcium, sodium, and potassium in blood plasma samples by capillary zone electrophoresis by Emirhan Nemutlu; Nuran Özaltın (pp. 833-838).
A capillary zone electrophoretic assay has been developed and validated for analysis of magnesium, calcium, sodium, and potassium in blood plasma samples. Optimum results were obtained with 20 mmol L−1 imidazole (pH 2.8) and 0.5 mmol L−1 oxalic acid containing 5% methanol, capillary temperature 25°C, applied voltage 30 kV, hydrodynamic injection time 3 s, and a poly(vinyl alcohol)-coated capillary (i.d. 50 μm, total length 64.5 cm and effective length 56 cm). Indirect detection was performed at 214 nm. Cadmium was used as internal standard. The migration times of magnesium, calcium, sodium, and potassium were 4.25, 3.79, 3.96, and 2.79 min, respectively. The method was applied to the determination of magnesium, calcium, sodium, and potassium in blood plasma samples. The results were compared with those from atomic absorption spectrophotometry and no statistically significant difference was found (P>0.05).
Keywords: Cation; CZE; Validation; Plasma
Determination of magnesium, calcium, sodium, and potassium in blood plasma samples by capillary zone electrophoresis by Emirhan Nemutlu; Nuran Özaltın (pp. 833-838).
A capillary zone electrophoretic assay has been developed and validated for analysis of magnesium, calcium, sodium, and potassium in blood plasma samples. Optimum results were obtained with 20 mmol L−1 imidazole (pH 2.8) and 0.5 mmol L−1 oxalic acid containing 5% methanol, capillary temperature 25°C, applied voltage 30 kV, hydrodynamic injection time 3 s, and a poly(vinyl alcohol)-coated capillary (i.d. 50 μm, total length 64.5 cm and effective length 56 cm). Indirect detection was performed at 214 nm. Cadmium was used as internal standard. The migration times of magnesium, calcium, sodium, and potassium were 4.25, 3.79, 3.96, and 2.79 min, respectively. The method was applied to the determination of magnesium, calcium, sodium, and potassium in blood plasma samples. The results were compared with those from atomic absorption spectrophotometry and no statistically significant difference was found (P>0.05).
Keywords: Cation; CZE; Validation; Plasma
Economic bismuth-film microsensor for anodic stripping analysis of trace heavy metals using differential pulse voltammetry by Sophie Legeai; Koïkoï Soropogui; Martin Cretinon; Olivier Vittori; Arno Heeren De Oliveira; Frédérique Barbier; Marie-Florence Grenier-Loustalot (pp. 839-847).
Stripping analysis has been widely recognised as a powerful tool in trace metal analysis. Its remarkable sensitivity is attributed to the combination of a preconcentration step coupled with pulse measurements that generate an extremely high signal-to-background ratio. Mercury-based electrodes have traditionally been used to achieve high reproducibility and sensitivity in the stripping technique. Because of the toxicity of mercury, however, new alternative electrode materials are highly desired, particularly for on-site monitoring. Use of thin films of bismuth deposited on platinum or glassy-carbon substrates has recently been proposed as a possible alternative to mercury—bismuth is “environmentally friendly”, of low toxicity, and is in widespread pharmaceutical use. In this paper the preparation of economic bismuth-film microelectrodes by electrodeposition on a copper substrate and their application to heavy metal analysis are described. Bismuth-film electrodes were prepared by potentiostatic electrodeposition. Optimum conditions for chemical and electrochemical deposition to obtain an adherent, reproducible, and robust deposit were determined. The suitability of such microelectrodes for analysis of heavy metals was evaluated by anodic stripping voltammetry of cadmium. The analytical performance of bismuth-film electrodes for anodic stripping voltammetry of heavy metals was evaluated for non-deaerated solutions containing Cd2+, Pb2+, and Zn2+ ions. Well-defined peaks with low background current were obtained by use of differential pulse voltammetry. Linear calibration plots were obtained for Cd2+ in acidified tap water at concentrations ranging from 2×10−8 to 1×10−7 mol L−1 and from 1×10−7 to 1×10−6 mol L−1 with relative standard deviations of 5% (n=15) at the 1×10−7 mol L−1 level. The method was then successfully used to monitor the Cd2+content of plant extracts and validated by polarographic and ICP−MS measurements. These results open the possibility of using bismuth-coated copper electrodes as an alternative to mercury-based electrodes for analysis of heavy metals. The main problem remaining, which prevents on-site monitoring of heavy metals, is the need to use slightly acidic media, because formation of bismuth hydroxide on the film surface above pH 4.3 leads to non-reproducible measurements. Further experiments will be performed to discover whether electrode conditioning can be used to enable reproducible measurement in on-site monitoring of cadmium in natural waters. Moreover, further study should be conducted to evaluate the potential of BiFE for analysis of several pollutants of interest that are usually determined electrochemically by using mercury-based electrodes.
Keywords: Bismuth-film electrodes; Copper substrate; Heavy metal analysis; Natural waters; Plant extracts
Economic bismuth-film microsensor for anodic stripping analysis of trace heavy metals using differential pulse voltammetry by Sophie Legeai; Koïkoï Soropogui; Martin Cretinon; Olivier Vittori; Arno Heeren De Oliveira; Frédérique Barbier; Marie-Florence Grenier-Loustalot (pp. 839-847).
Stripping analysis has been widely recognised as a powerful tool in trace metal analysis. Its remarkable sensitivity is attributed to the combination of a preconcentration step coupled with pulse measurements that generate an extremely high signal-to-background ratio. Mercury-based electrodes have traditionally been used to achieve high reproducibility and sensitivity in the stripping technique. Because of the toxicity of mercury, however, new alternative electrode materials are highly desired, particularly for on-site monitoring. Use of thin films of bismuth deposited on platinum or glassy-carbon substrates has recently been proposed as a possible alternative to mercury—bismuth is “environmentally friendly”, of low toxicity, and is in widespread pharmaceutical use. In this paper the preparation of economic bismuth-film microelectrodes by electrodeposition on a copper substrate and their application to heavy metal analysis are described. Bismuth-film electrodes were prepared by potentiostatic electrodeposition. Optimum conditions for chemical and electrochemical deposition to obtain an adherent, reproducible, and robust deposit were determined. The suitability of such microelectrodes for analysis of heavy metals was evaluated by anodic stripping voltammetry of cadmium. The analytical performance of bismuth-film electrodes for anodic stripping voltammetry of heavy metals was evaluated for non-deaerated solutions containing Cd2+, Pb2+, and Zn2+ ions. Well-defined peaks with low background current were obtained by use of differential pulse voltammetry. Linear calibration plots were obtained for Cd2+ in acidified tap water at concentrations ranging from 2×10−8 to 1×10−7 mol L−1 and from 1×10−7 to 1×10−6 mol L−1 with relative standard deviations of 5% (n=15) at the 1×10−7 mol L−1 level. The method was then successfully used to monitor the Cd2+content of plant extracts and validated by polarographic and ICP−MS measurements. These results open the possibility of using bismuth-coated copper electrodes as an alternative to mercury-based electrodes for analysis of heavy metals. The main problem remaining, which prevents on-site monitoring of heavy metals, is the need to use slightly acidic media, because formation of bismuth hydroxide on the film surface above pH 4.3 leads to non-reproducible measurements. Further experiments will be performed to discover whether electrode conditioning can be used to enable reproducible measurement in on-site monitoring of cadmium in natural waters. Moreover, further study should be conducted to evaluate the potential of BiFE for analysis of several pollutants of interest that are usually determined electrochemically by using mercury-based electrodes.
Keywords: Bismuth-film electrodes; Copper substrate; Heavy metal analysis; Natural waters; Plant extracts
Investigation of compound-independent calibration and partial molecular formula determination by gas chromatography–atomic-emission detection for characterisation of organophosphorus and organosulfur agents related to the chemical weapons convention by Yannick Juillet; Edmond Gibert; Arlette Bégos; Bruno Bellier (pp. 848-856).
Atomic-emission detection (AED) is a technique particularly-well suited to screening complex samples for multiple compounds containing heteroatoms such as phosphorus, sulfur, or nitrogen, which are especially relevant in verification of chemical disarmament. Among other GC detectors, AED has unique characteristics such as compound-independent calibration and possible raw-formula determination. Because contradictory results have been reported on these points, we set up a study with the objectives not only of applying these techniques to chemical weapons convention-related chemicals but of determining under which conditions they would yield satisfactory results. The extensive data collected in this study are evidence that the response of the detector, particularly for the phosphorus line, is very dependent on the molecular mass and concentration of the chemicals analysed whereas molecular structure seems to have less effect on the AED signal. Most interestingly, compound-independent calibration and subsequent partial molecular formula determination usually seem satisfactory when the reference compounds used to calibrate the system have GC retention times and molecular masses close to those of the unknown analytes (whose molecular mass may be determined by GC–CI-MS). We therefore suggest the use of a reference set of compounds covering a large chromatographic window, which enables the selection, within this set, of the most appropriate reference compound for calibration and for determination of the raw formula of an unknown analyte. For optimal performance, the use of a new discharge tube is also recommended.
Keywords: Atomic-emission detector; Compound-independent calibration; Raw-formula determination; Organophosphorus; Chemical warfare agents
Investigation of compound-independent calibration and partial molecular formula determination by gas chromatography–atomic-emission detection for characterisation of organophosphorus and organosulfur agents related to the chemical weapons convention by Yannick Juillet; Edmond Gibert; Arlette Bégos; Bruno Bellier (pp. 848-856).
Atomic-emission detection (AED) is a technique particularly-well suited to screening complex samples for multiple compounds containing heteroatoms such as phosphorus, sulfur, or nitrogen, which are especially relevant in verification of chemical disarmament. Among other GC detectors, AED has unique characteristics such as compound-independent calibration and possible raw-formula determination. Because contradictory results have been reported on these points, we set up a study with the objectives not only of applying these techniques to chemical weapons convention-related chemicals but of determining under which conditions they would yield satisfactory results. The extensive data collected in this study are evidence that the response of the detector, particularly for the phosphorus line, is very dependent on the molecular mass and concentration of the chemicals analysed whereas molecular structure seems to have less effect on the AED signal. Most interestingly, compound-independent calibration and subsequent partial molecular formula determination usually seem satisfactory when the reference compounds used to calibrate the system have GC retention times and molecular masses close to those of the unknown analytes (whose molecular mass may be determined by GC–CI-MS). We therefore suggest the use of a reference set of compounds covering a large chromatographic window, which enables the selection, within this set, of the most appropriate reference compound for calibration and for determination of the raw formula of an unknown analyte. For optimal performance, the use of a new discharge tube is also recommended.
Keywords: Atomic-emission detector; Compound-independent calibration; Raw-formula determination; Organophosphorus; Chemical warfare agents
Occurrence of endocrine-disrupting compounds in reclaimed water from Tianjin, China by Yuqiu Wang; Wei Hu; Zhonghong Cao; Xueqi Fu; Tan Zhu (pp. 857-863).
Continuous disposal of endocrine-disrupting compounds (EDCs) into the environment can lead to serious human health problems and can affect plants and aquatic organisms. The determination of EDCs in water has become an increasingly important activity due to our increased knowledge about their toxicities, even at low concentration. The EDCs in water samples from the reclaimed water plant of Tianjin, northern China, were identified by gas chromatography (GC)–mass spectrometry (MS). Important and contrasting EDCs including estrone (E1), 17β-estradiol (E2), 17α-ethynylestradiol (EE2), 4-tert-octylphenol (OP), 4-nonylphenol (NP), bisphenol A (BPA), di-n-butyl phthalate (DnBP), diisobutyl phthalate (DIBP), and di(2-ethylhexyl)phthalate (DEHP) were selected as the target compounds. Concentrations of steroid hormones, alkylphenolic compounds and phthalates ranged from below the limit of detection (LOD) to 8.1 ng L−1, from −1, and from 1.00 μg L−1 to 23.8 μg L−1, respectively. The average removal efficiencies for target EDCs varied from 30% to 82%. These results indicate that environmental endocrine disrupting compounds are not completely removed during reclaimed water treatment and may be carried over into the general aquatic environment.
Keywords: Endocrine disrupting compounds (EDCs); Steroid hormones; Alkylphenolic compounds; Phthalates; Reclaimed water
Occurrence of endocrine-disrupting compounds in reclaimed water from Tianjin, China by Yuqiu Wang; Wei Hu; Zhonghong Cao; Xueqi Fu; Tan Zhu (pp. 857-863).
Continuous disposal of endocrine-disrupting compounds (EDCs) into the environment can lead to serious human health problems and can affect plants and aquatic organisms. The determination of EDCs in water has become an increasingly important activity due to our increased knowledge about their toxicities, even at low concentration. The EDCs in water samples from the reclaimed water plant of Tianjin, northern China, were identified by gas chromatography (GC)–mass spectrometry (MS). Important and contrasting EDCs including estrone (E1), 17β-estradiol (E2), 17α-ethynylestradiol (EE2), 4-tert-octylphenol (OP), 4-nonylphenol (NP), bisphenol A (BPA), di-n-butyl phthalate (DnBP), diisobutyl phthalate (DIBP), and di(2-ethylhexyl)phthalate (DEHP) were selected as the target compounds. Concentrations of steroid hormones, alkylphenolic compounds and phthalates ranged from below the limit of detection (LOD) to 8.1 ng L−1, from −1, and from 1.00 μg L−1 to 23.8 μg L−1, respectively. The average removal efficiencies for target EDCs varied from 30% to 82%. These results indicate that environmental endocrine disrupting compounds are not completely removed during reclaimed water treatment and may be carried over into the general aquatic environment.
Keywords: Endocrine disrupting compounds (EDCs); Steroid hormones; Alkylphenolic compounds; Phthalates; Reclaimed water
The detection of formaldehyde in textiles using interdigitated microelectrode array diffusion layer titration with electrogenerated hypobromite by Peter Tomčík; Pavlína Jenčušová; Monika Krajčíková; Dušan Bustin; Roman Brescher (pp. 864-868).
An interdigitated microelectrode array (IDA) was applied to the determination of formaldehyde released from textiles produced in industry. The proposed method is based on formaldehyde reaction with hypobromite which is formed in weakly basic media by control current electrooxidation of bromide on the generator segment of the IDA array. The unreacted hypobromite diffuses through the gap between individually polarisable IDA segments and it is amperometrically detected on the collector segment of the IDA. The efficiency of this nonconvective transfer process in the absence of formaldehyde was substantially higher (78%) in comparison with that when using the rotating ring disc electrode. The influence of the added formaldehyde on the transfer process can be utilised to develop a simple and sensitive analytical procedure for formaldehyde detection with a detection limit of 4×10−6 mol dm−3.
Keywords: Formaldehyde; Interdigitated microelectrode array; Hypobromite; Environmental pollutants
The detection of formaldehyde in textiles using interdigitated microelectrode array diffusion layer titration with electrogenerated hypobromite by Peter Tomčík; Pavlína Jenčušová; Monika Krajčíková; Dušan Bustin; Roman Brescher (pp. 864-868).
An interdigitated microelectrode array (IDA) was applied to the determination of formaldehyde released from textiles produced in industry. The proposed method is based on formaldehyde reaction with hypobromite which is formed in weakly basic media by control current electrooxidation of bromide on the generator segment of the IDA array. The unreacted hypobromite diffuses through the gap between individually polarisable IDA segments and it is amperometrically detected on the collector segment of the IDA. The efficiency of this nonconvective transfer process in the absence of formaldehyde was substantially higher (78%) in comparison with that when using the rotating ring disc electrode. The influence of the added formaldehyde on the transfer process can be utilised to develop a simple and sensitive analytical procedure for formaldehyde detection with a detection limit of 4×10−6 mol dm−3.
Keywords: Formaldehyde; Interdigitated microelectrode array; Hypobromite; Environmental pollutants
Matrix solid phase dispersion–Soxhlet simultaneous extraction clean-up for determination of organochlorine pesticide residues in tobacco by Jibao Cai; Yun Gao; Xiaolan Zhu; Qingde Su (pp. 869-874).
A novel method combining matrix solid phase dispersion (MSPD) with Soxhlet simultaneous extraction clean-up (SSEC) was developed. Being a single-step extraction and clean-up procedure, it could be used instead of multistep solvent extraction and Florisol column clean-up. It not only reduces sample contamination during the procedure, but it also decreases the amount of organic solvent needed. The retention times of standards were used to qualitatively assess the method, and the external standard method was used to quantitatively assess it. Residues of organochlorine pesticides (OCP) in tobaccos were determined by gas chromatography–electron capture detection (GC–ECD), and their identities were confirmed by the standard addition method (SAM). The performance of the method was evaluated and validated: the detection limit was 0.01–0.02 μg g−1, relative standard deviations were 5–26%, and recoveries were 72–99% at fortification levels of 0.10, 1.00 and 10.0 μg g−1. The analytical characteristics of MSPD–SSEC compared very favorably with the results from the classical multistep solvent extraction and Florisol column clean-up method.
Keywords: MSPD–SSEC; OCP; GC; Tobacco
Matrix solid phase dispersion–Soxhlet simultaneous extraction clean-up for determination of organochlorine pesticide residues in tobacco by Jibao Cai; Yun Gao; Xiaolan Zhu; Qingde Su (pp. 869-874).
A novel method combining matrix solid phase dispersion (MSPD) with Soxhlet simultaneous extraction clean-up (SSEC) was developed. Being a single-step extraction and clean-up procedure, it could be used instead of multistep solvent extraction and Florisol column clean-up. It not only reduces sample contamination during the procedure, but it also decreases the amount of organic solvent needed. The retention times of standards were used to qualitatively assess the method, and the external standard method was used to quantitatively assess it. Residues of organochlorine pesticides (OCP) in tobaccos were determined by gas chromatography–electron capture detection (GC–ECD), and their identities were confirmed by the standard addition method (SAM). The performance of the method was evaluated and validated: the detection limit was 0.01–0.02 μg g−1, relative standard deviations were 5–26%, and recoveries were 72–99% at fortification levels of 0.10, 1.00 and 10.0 μg g−1. The analytical characteristics of MSPD–SSEC compared very favorably with the results from the classical multistep solvent extraction and Florisol column clean-up method.
Keywords: MSPD–SSEC; OCP; GC; Tobacco
Determination of vitamin B1 in seawater and microalgal fermentation media by high-performance liquid chromatography with fluorescence detection by Hong-Zhi He; Hua-Bin Li; Feng Chen (pp. 875-879).
A highly sensitive high-performance liquid chromatographic method with fluorescence detection has been developed for determination of vitamin B1. Vitamin B1 was converted into a fluorescent compound by treatment with hydrogen peroxide–horseradish peroxidase and the derivative was subsequently analyzed by HPLC on a Waters Spherisorb ODS2 column (250 mm×4.6 mm ID, 5 μm) with 40:60 methanol–pH 8.5 acetate buffer solution as mobile phase and fluorescence detection at 440 nm (with excitation at 375 nm). The calibration graph was linear from 5.00×10−10 mol L−1 to 5.00×10−7 mol L−1 for vitamin B1 with a correlation coefficient of 0.9991 (n=9). The detection limit was 1.0×10−10 mol L−1. The method was successfully used for determination of vitamin B1 at pg mL−1 levels in microalgal fermentation media and seawater after solid-phase extraction. Recovery was from 89 to 110% and the relative standard deviation was in the range 1.1 to 4.3%.
Keywords: Vitamin B1 ; High-performance liquid chromatography; Solid-phase extraction; Fermentation media; Seawater
Determination of vitamin B1 in seawater and microalgal fermentation media by high-performance liquid chromatography with fluorescence detection by Hong-Zhi He; Hua-Bin Li; Feng Chen (pp. 875-879).
A highly sensitive high-performance liquid chromatographic method with fluorescence detection has been developed for determination of vitamin B1. Vitamin B1 was converted into a fluorescent compound by treatment with hydrogen peroxide–horseradish peroxidase and the derivative was subsequently analyzed by HPLC on a Waters Spherisorb ODS2 column (250 mm×4.6 mm ID, 5 μm) with 40:60 methanol–pH 8.5 acetate buffer solution as mobile phase and fluorescence detection at 440 nm (with excitation at 375 nm). The calibration graph was linear from 5.00×10−10 mol L−1 to 5.00×10−7 mol L−1 for vitamin B1 with a correlation coefficient of 0.9991 (n=9). The detection limit was 1.0×10−10 mol L−1. The method was successfully used for determination of vitamin B1 at pg mL−1 levels in microalgal fermentation media and seawater after solid-phase extraction. Recovery was from 89 to 110% and the relative standard deviation was in the range 1.1 to 4.3%.
Keywords: Vitamin B1 ; High-performance liquid chromatography; Solid-phase extraction; Fermentation media; Seawater
Study of the voltammetric behaviour of metam and its application to an amperometric flow system by M. Fátima Barroso; Paula Paíga; M. Carmo V. F. Vaz; Cristina Delerue-Matos (pp. 880-885).
The electrochemical behaviour of the pesticide metam (MT) at a glassy carbon working electrode (GCE) and at a hanging mercury drop electrode (HMDE) was investigated. Different voltammetric techniques, including cyclic voltammetry (CV) and square wave voltammetry (SWV), were used. An anodic peak (independent of pH) at +1.46 V vs AgCl/Ag was observed in MT aqueous solution using the GCE. SWV calibration curves were plotted under optimized conditions (pH 2.5 and frequency 50 Hz), which showed a linear response for 17–29 mg L−1. Electrochemical reduction was also explored, using the HMDE. A well defined cathodic peak was recorded at −0.72 V vs AgCl/Ag, dependent on pH. After optimizing the operating conditions (pH 10.1, frequency 150 Hz, potential deposition −0.20 V for 10 s), calibration curves was measured in the concentration range 2.5×10−1 to 1.0 mg L−1 using SWV. The electrochemical behaviour of this compound facilitated the development of a flow injection analysis (FIA) system with amperometric detection for the quantification of MT in commercial formulations and spiked water samples. An assessment of the optimal FIA conditions indicated that the best analytical results were obtained at a potential of +1.30 V, an injection volume of 207 μL and an overall flow rate of 2.4 ml min−1. Real samples were analysed via calibration curves over the concentration range 1.3×10−2 to 1.3 mg L−1. Recoveries from the real samples (spiked waters and commercial formulations) were between 97.4 and 105.5%. The precision of the proposed method was evaluated by assessing the relative standard deviation (RSD %) of ten consecutive determinations of one sample (1.0 mg L−1), and the value obtained was 1.5%.
Keywords: Metam; Glassy carbon electrode; Hanging mercury drop electrode; Flow injection amperometric system
Study of the voltammetric behaviour of metam and its application to an amperometric flow system by M. Fátima Barroso; Paula Paíga; M. Carmo V. F. Vaz; Cristina Delerue-Matos (pp. 880-885).
The electrochemical behaviour of the pesticide metam (MT) at a glassy carbon working electrode (GCE) and at a hanging mercury drop electrode (HMDE) was investigated. Different voltammetric techniques, including cyclic voltammetry (CV) and square wave voltammetry (SWV), were used. An anodic peak (independent of pH) at +1.46 V vs AgCl/Ag was observed in MT aqueous solution using the GCE. SWV calibration curves were plotted under optimized conditions (pH 2.5 and frequency 50 Hz), which showed a linear response for 17–29 mg L−1. Electrochemical reduction was also explored, using the HMDE. A well defined cathodic peak was recorded at −0.72 V vs AgCl/Ag, dependent on pH. After optimizing the operating conditions (pH 10.1, frequency 150 Hz, potential deposition −0.20 V for 10 s), calibration curves was measured in the concentration range 2.5×10−1 to 1.0 mg L−1 using SWV. The electrochemical behaviour of this compound facilitated the development of a flow injection analysis (FIA) system with amperometric detection for the quantification of MT in commercial formulations and spiked water samples. An assessment of the optimal FIA conditions indicated that the best analytical results were obtained at a potential of +1.30 V, an injection volume of 207 μL and an overall flow rate of 2.4 ml min−1. Real samples were analysed via calibration curves over the concentration range 1.3×10−2 to 1.3 mg L−1. Recoveries from the real samples (spiked waters and commercial formulations) were between 97.4 and 105.5%. The precision of the proposed method was evaluated by assessing the relative standard deviation (RSD %) of ten consecutive determinations of one sample (1.0 mg L−1), and the value obtained was 1.5%.
Keywords: Metam; Glassy carbon electrode; Hanging mercury drop electrode; Flow injection amperometric system
Determination of jasmonic acid in Lemna minor (L.) by liquid chromatography with fluorescence detection by Janja Kristl; Marjan Veber; Božidar Krajničič; Klara Orešnik; Metka Slekovec (pp. 886-893).
A new method is described for the determination of endogenous jasmonic acid (JA) in Lemna minor plant extracts using liquid chromatography (LC) with fluorescence detection. Plant tissues were extracted and derivatised using 9-anthryldiazomethane (ADAM reagent) prepared in situ. Accuracy and precision were improved by using the internal standard dihydrojasmonic acid (dh-JA) for the correction of JA losses during sample preparation steps. Liquid chromatography–mass spectrometry (LC/MS) analysis of ADAM derivatives of JA and dh-JA confirmed that a single molecule of JA and dh-JA was coupled with one molecule of reagent. Derivatives of JA and dh-JA were separated with gradient elution on a C18 reversed-phase column using acetonitrile/water as a mobile phase and detected by a fluorescence detector at excitation and emission wavelengths of 254 and 412 nm, respectively. The detection limits of JA and dh-JA were 2.9 ng mL−1 and 3.7 ng mL−1 per 50-μL injection. The method is reproducible and selective and yields single peaks for each compound regardless of isomer. The specificity and accuracy of the proposed LC/FD method was confirmed by liquid chromatography–TurboIon Spray tandem mass spectrometric (LC/MS/MS) analysis of free JA in Lemna minor samples under multiple reaction monitoring conditions.
Keywords: Jasmonic acid; 9-Anthryldiazomethane; Liquid chromatography; Mass spectrometry; Lemna minor (L.)
Determination of jasmonic acid in Lemna minor (L.) by liquid chromatography with fluorescence detection by Janja Kristl; Marjan Veber; Božidar Krajničič; Klara Orešnik; Metka Slekovec (pp. 886-893).
A new method is described for the determination of endogenous jasmonic acid (JA) in Lemna minor plant extracts using liquid chromatography (LC) with fluorescence detection. Plant tissues were extracted and derivatised using 9-anthryldiazomethane (ADAM reagent) prepared in situ. Accuracy and precision were improved by using the internal standard dihydrojasmonic acid (dh-JA) for the correction of JA losses during sample preparation steps. Liquid chromatography–mass spectrometry (LC/MS) analysis of ADAM derivatives of JA and dh-JA confirmed that a single molecule of JA and dh-JA was coupled with one molecule of reagent. Derivatives of JA and dh-JA were separated with gradient elution on a C18 reversed-phase column using acetonitrile/water as a mobile phase and detected by a fluorescence detector at excitation and emission wavelengths of 254 and 412 nm, respectively. The detection limits of JA and dh-JA were 2.9 ng mL−1 and 3.7 ng mL−1 per 50-μL injection. The method is reproducible and selective and yields single peaks for each compound regardless of isomer. The specificity and accuracy of the proposed LC/FD method was confirmed by liquid chromatography–TurboIon Spray tandem mass spectrometric (LC/MS/MS) analysis of free JA in Lemna minor samples under multiple reaction monitoring conditions.
Keywords: Jasmonic acid; 9-Anthryldiazomethane; Liquid chromatography; Mass spectrometry; Lemna minor (L.)