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Analytical and Bioanalytical Chemistry (v.385, #4)
Jonathan M. Cooper and Anthony E.G. Cass (Eds): Biosensors, 2nd edition
by Jan Jaehrling (pp. 663-664).
Jonathan M. Cooper and Anthony E.G. Cass (Eds): Biosensors, 2nd edition
by Jan Jaehrling (pp. 663-664).
Determination of thallium in biological samples by Arabinda K. Das; Ruma Chakraborty; M. Luisa Cervera; Miguel de la Guardia (pp. 665-670).
Determination of thallium has become a major interest because of its high toxicity, especially as the monovalent cation. Thallium poisoning in the human body must be checked quickly by analysis of biological samples. This review highlights the development of highly sensitive detection techniques applied to the determination of thallium in biological samples, with or without pretreatment, based on the literature compiled in Analytical Abstracts from 1990.
Keywords: Review; Thallium; Biological samples; Method comparability
Determination of thallium in biological samples by Arabinda K. Das; Ruma Chakraborty; M. Luisa Cervera; Miguel de la Guardia (pp. 665-670).
Determination of thallium has become a major interest because of its high toxicity, especially as the monovalent cation. Thallium poisoning in the human body must be checked quickly by analysis of biological samples. This review highlights the development of highly sensitive detection techniques applied to the determination of thallium in biological samples, with or without pretreatment, based on the literature compiled in Analytical Abstracts from 1990.
Keywords: Review; Thallium; Biological samples; Method comparability
On-column sample enrichment for the high-sensitivity sheath-flow CE-MS analysis of peptides by K. Sandra; F. Lynen; B. Devreese; J. Van Beeumen; P. Sandra (pp. 671-677).
A sample enrichment technique to increase sensitivity in capillary electrophoresis–mass spectrometry (CE-MS) is described. Peptides or glycopeptides are retained and concentrated on a short (3–5-mm) reversed-phase (C18) packed-bed situated in the fused-silica separation capillary and are subsequently released for electrophoretic separation by injection of an organic elutant. The concentration limits of detection are in the high picomolar range with a sheath-flow CE-MS interface.
Keywords: Capillary electrophoresis; Mass spectrometry; Peptides; In-line preconcentration
On-column sample enrichment for the high-sensitivity sheath-flow CE-MS analysis of peptides by K. Sandra; F. Lynen; B. Devreese; J. Van Beeumen; P. Sandra (pp. 671-677).
A sample enrichment technique to increase sensitivity in capillary electrophoresis–mass spectrometry (CE-MS) is described. Peptides or glycopeptides are retained and concentrated on a short (3–5-mm) reversed-phase (C18) packed-bed situated in the fused-silica separation capillary and are subsequently released for electrophoretic separation by injection of an organic elutant. The concentration limits of detection are in the high picomolar range with a sheath-flow CE-MS interface.
Keywords: Capillary electrophoresis; Mass spectrometry; Peptides; In-line preconcentration
Progress toward the development of a point-of-care photonic crystal ammonia sensor by Kyle W. Kimble; Jeremy P. Walker; David N. Finegold; Sanford A. Asher (pp. 678-685).
We have developed an ammonia-sensitive material by coupling the Berthelot reaction to our polymerized crystalline colloidal array (PCCA) technology. The material consists of a periodic array of highly charged colloidal particles (110 nm diameter) embedded in a poly(hydroxyethyl acrylate) hydrogel. The particles have a lattice spacing such that they Bragg-diffract visible light. In the Berthelot reaction, ammonia, hypochlorite, and phenol react to produce the dye molecule indophenol blue in an aqueous solution. We use this reaction in our sensor by covalently attaching 3-aminophenol to the hydrogel backbone, which forms cross-links through the Berthelot mechanism. Ammonia reacts with hypochlorite, forming monochloramine, which then reacts with a pendant aminophenol to form a benzoquinone chlorimine. The benzoquinone chlorimine reacts with another pendant aminophenol to form a cross-link. The creation of new cross-links causes the hydrogel to shrink, which reduces the lattice spacing of the embedded colloidal array. This volume change results in a blue-shift in the diffracted light proportional to the concentration of NH3 in the sample. We demonstrate that the NH3 photonic crystal sensing material is capable of quantitative determination of concentrations in the physiological range (50–350 μmol NH3 L−1) in human blood serum.
Keywords: Sensor; Ammonia; Point-of-care; Polymerized crystalline colloidal array (PCCA); Hydrogels; Photonic crystal
Progress toward the development of a point-of-care photonic crystal ammonia sensor by Kyle W. Kimble; Jeremy P. Walker; David N. Finegold; Sanford A. Asher (pp. 678-685).
We have developed an ammonia-sensitive material by coupling the Berthelot reaction to our polymerized crystalline colloidal array (PCCA) technology. The material consists of a periodic array of highly charged colloidal particles (110 nm diameter) embedded in a poly(hydroxyethyl acrylate) hydrogel. The particles have a lattice spacing such that they Bragg-diffract visible light. In the Berthelot reaction, ammonia, hypochlorite, and phenol react to produce the dye molecule indophenol blue in an aqueous solution. We use this reaction in our sensor by covalently attaching 3-aminophenol to the hydrogel backbone, which forms cross-links through the Berthelot mechanism. Ammonia reacts with hypochlorite, forming monochloramine, which then reacts with a pendant aminophenol to form a benzoquinone chlorimine. The benzoquinone chlorimine reacts with another pendant aminophenol to form a cross-link. The creation of new cross-links causes the hydrogel to shrink, which reduces the lattice spacing of the embedded colloidal array. This volume change results in a blue-shift in the diffracted light proportional to the concentration of NH3 in the sample. We demonstrate that the NH3 photonic crystal sensing material is capable of quantitative determination of concentrations in the physiological range (50–350 μmol NH3 L−1) in human blood serum.
Keywords: Sensor; Ammonia; Point-of-care; Polymerized crystalline colloidal array (PCCA); Hydrogels; Photonic crystal
Short polystyrene monolith-fritted micro-liquid chromatography columns for rapid isocratic analysis of pharmaceuticals direct from plasma by Cristina Legido-Quigley; Norman W. Smith (pp. 686-691).
The manufacture of micro-HPLC columns with combined stationary phases, a body of 3.5-μm XTerra-C18 particles, and poly(styrene–divinylbenzene) (PS–DVB) frits is described in detail. The efficiency of the columns was assessed by rapid separation of neutral and acid compound mixtures. Direct analysis of some pharmaceuticals in plasma resulted in lower limits of detection (LOD) for salmeterol xinofate of 12.5 nanograms on-column.
Keywords: Monolith frit; Stationary phases; MicroLC
Short polystyrene monolith-fritted micro-liquid chromatography columns for rapid isocratic analysis of pharmaceuticals direct from plasma by Cristina Legido-Quigley; Norman W. Smith (pp. 686-691).
The manufacture of micro-HPLC columns with combined stationary phases, a body of 3.5-μm XTerra-C18 particles, and poly(styrene–divinylbenzene) (PS–DVB) frits is described in detail. The efficiency of the columns was assessed by rapid separation of neutral and acid compound mixtures. Direct analysis of some pharmaceuticals in plasma resulted in lower limits of detection (LOD) for salmeterol xinofate of 12.5 nanograms on-column.
Keywords: Monolith frit; Stationary phases; MicroLC
Strategies for examination of Alzheimer’s disease amyloid precursor protein isoforms by Jillian R. A. Newton; David Parkinson; Malcolm R. Clench (pp. 692-699).
We describe a proteomics procedure using bioinformatics, immunoprecipitation, two-dimensional gel electrophoresis, Western blotting, in-gel digestion, LC–MS, MALDI–MS, and MS–MS for isolation and identification of amyloid precursor protein (APP) isoforms APP695, APP751, and APP770. Retinoic acid-induced Ntera 2 cell line, derived from a human teratocarcinoma cells, was the in-vitro source of APP. Initial isolation of whole APP was performed by immunoprecipitation, using AB10, a monoclonal antibody raised to amino acids 1–17 of the β-amyloid peptide sequence, which is present in all three alpha secretase-cleaved isoforms of interest. The next stage was separation of whole APP into its isoform components by two-dimensional gel electrophoresis. Because of low APP concentrations, detection by the usual staining methods, for example Sypro Ruby, able to detect low picomole concentrations, did not enable visualisation of the isoforms. Western analysis, however, enabled primary detection of APP, because of the inherent sensitivity of antibodies raised to specific isoform regions. This initial visualization acted as a template for excision of isoforms from 2D gels, which were then subjected to peptide mass mapping. Initial theoretical digestion of each isoform revealed the presence of specific peptides, which were then used as “tags” for isoform detection.
Keywords: Amyloid precursor protein; Isoforms; Proteomics; Mass spectrometry
Strategies for examination of Alzheimer’s disease amyloid precursor protein isoforms by Jillian R. A. Newton; David Parkinson; Malcolm R. Clench (pp. 692-699).
We describe a proteomics procedure using bioinformatics, immunoprecipitation, two-dimensional gel electrophoresis, Western blotting, in-gel digestion, LC–MS, MALDI–MS, and MS–MS for isolation and identification of amyloid precursor protein (APP) isoforms APP695, APP751, and APP770. Retinoic acid-induced Ntera 2 cell line, derived from a human teratocarcinoma cells, was the in-vitro source of APP. Initial isolation of whole APP was performed by immunoprecipitation, using AB10, a monoclonal antibody raised to amino acids 1–17 of the β-amyloid peptide sequence, which is present in all three alpha secretase-cleaved isoforms of interest. The next stage was separation of whole APP into its isoform components by two-dimensional gel electrophoresis. Because of low APP concentrations, detection by the usual staining methods, for example Sypro Ruby, able to detect low picomole concentrations, did not enable visualisation of the isoforms. Western analysis, however, enabled primary detection of APP, because of the inherent sensitivity of antibodies raised to specific isoform regions. This initial visualization acted as a template for excision of isoforms from 2D gels, which were then subjected to peptide mass mapping. Initial theoretical digestion of each isoform revealed the presence of specific peptides, which were then used as “tags” for isoform detection.
Keywords: Amyloid precursor protein; Isoforms; Proteomics; Mass spectrometry
Structural and chemical characterisation of titanium deuteride films covered by nanoscale evaporated palladium layers by W. Lisowski; E. G. Keim; A. H. J. van den Berg; M. A. Smithers (pp. 700-707).
Thin titanium deuteride (TiDy) films, covered by an ultra-thin palladium layer, have been compared with the corresponding titanium and palladium films using a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The TiDy layers were prepared under ultra-high vacuum (UHV) conditions by precisely controlled deuterium sorption at 298 K on a Ti film evaporated onto a Si(100) substrate. Both Ti and TiDy films were then covered in situ by a nanoscale Pd layer. It was found that a 10- to 12-nm-thick Pd layer protects the TiDy films efficiently against extensive air interaction. The morphology of both the surface and bulk Pd/TiDy (Ti) films have been observed using SEM and cross-sectional TEM analysis, respectively. A polycrystalline bulk morphology in both Ti and TiDy films accompanied by a fine-grained Pd surface was observed. High-magnification cross-sectional TEM images reveal the TiDy film to be plastically deformed leading to an increase in the roughness of the top Pd layer. Complex structures, including Moiré patterns, have been identified within the Pd/TiDy interface. The chemical nature of this interface has been analysed after partial sputtering of the Pd top layer using XPS. Besides TiDy and Pd, TiO and PdO were found to be the main chemical species in the interface region of the Pd/TiHy film. The XPS valence-band spectra of the Pd/TiDy interface reveal electronic features characteristic of a Pd–Ti bimetallic structure.
Keywords: Titanium deuteride; SEM; TEM; XPS
Structural and chemical characterisation of titanium deuteride films covered by nanoscale evaporated palladium layers by W. Lisowski; E. G. Keim; A. H. J. van den Berg; M. A. Smithers (pp. 700-707).
Thin titanium deuteride (TiDy) films, covered by an ultra-thin palladium layer, have been compared with the corresponding titanium and palladium films using a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The TiDy layers were prepared under ultra-high vacuum (UHV) conditions by precisely controlled deuterium sorption at 298 K on a Ti film evaporated onto a Si(100) substrate. Both Ti and TiDy films were then covered in situ by a nanoscale Pd layer. It was found that a 10- to 12-nm-thick Pd layer protects the TiDy films efficiently against extensive air interaction. The morphology of both the surface and bulk Pd/TiDy (Ti) films have been observed using SEM and cross-sectional TEM analysis, respectively. A polycrystalline bulk morphology in both Ti and TiDy films accompanied by a fine-grained Pd surface was observed. High-magnification cross-sectional TEM images reveal the TiDy film to be plastically deformed leading to an increase in the roughness of the top Pd layer. Complex structures, including Moiré patterns, have been identified within the Pd/TiDy interface. The chemical nature of this interface has been analysed after partial sputtering of the Pd top layer using XPS. Besides TiDy and Pd, TiO and PdO were found to be the main chemical species in the interface region of the Pd/TiHy film. The XPS valence-band spectra of the Pd/TiDy interface reveal electronic features characteristic of a Pd–Ti bimetallic structure.
Keywords: Titanium deuteride; SEM; TEM; XPS
Evaluation of the application of attenuated total reflectance–Fourier transform infrared spectrometry (ATR–FTIR) and chemometrics to the determination of nutritional parameters of yogurt samples by J. Moros; F. A. Iñón; M. Khanmohammadi; S. Garrigues; M. de la Guardia (pp. 708-715).
A critical evaluation of the application of attenuated total reflectance–Fourier transform infrared spectroscopy (ATR–FTIR) and partial least squares (PLS) to the determination of several nutritional parameters, such as the energetic value and the carbohydrate, protein and calcium contents, in commercially available yogurt samples was carried out. To this end, a highly heterogeneous population of 48 samples covering a wide range of yogurts obtained from the Spanish market was used. After correcting the spectra, hierarchical cluster analysis was performed in order to select a representative calibration set and the corresponding validation sample set. Different PLS models and several spectral windows were tested in order to evaluate their prediction capabilities for the validation set. For all nutritional parameters, with the exception of fat content, the procedure developed here provided good precision; the values obtained complied with the statutory values declared by the US FDA.
Keywords: Carbohydrates; Fat; Protein; Calories; Yogurt; Hierarchical cluster analysis; PLS; Attenuated total reflectance; Infrared
Evaluation of the application of attenuated total reflectance–Fourier transform infrared spectrometry (ATR–FTIR) and chemometrics to the determination of nutritional parameters of yogurt samples by J. Moros; F. A. Iñón; M. Khanmohammadi; S. Garrigues; M. de la Guardia (pp. 708-715).
A critical evaluation of the application of attenuated total reflectance–Fourier transform infrared spectroscopy (ATR–FTIR) and partial least squares (PLS) to the determination of several nutritional parameters, such as the energetic value and the carbohydrate, protein and calcium contents, in commercially available yogurt samples was carried out. To this end, a highly heterogeneous population of 48 samples covering a wide range of yogurts obtained from the Spanish market was used. After correcting the spectra, hierarchical cluster analysis was performed in order to select a representative calibration set and the corresponding validation sample set. Different PLS models and several spectral windows were tested in order to evaluate their prediction capabilities for the validation set. For all nutritional parameters, with the exception of fat content, the procedure developed here provided good precision; the values obtained complied with the statutory values declared by the US FDA.
Keywords: Carbohydrates; Fat; Protein; Calories; Yogurt; Hierarchical cluster analysis; PLS; Attenuated total reflectance; Infrared
Optimization of the assay of naphthodianthrones in dry St John’s wort extract by reversed-phase liquid chromatography by Guilhem Pages; Michael Mazarin; Michelle Sergent; Roger Phan-Tan-Luu; Corinne Delaurent (pp. 716-723).
An optimization procedure for the reversed-phase liquid chromatography (RPLC) assay of naphthodianthrones in St John’s wort extract from the European Pharmacopoeia project is described. The results obtained from two screening designs showed that light exposure, recommended in the monograph as sample pretreatment, does not permit one to obtain a reproducible quantification of the main ingredients. Improvement of the method robustness implies the need to overcome the problem of light exposure, to subsequently quantify protonaphthodianthrones and to perform the separation on octadecyl (ODS)-bonded phase at optimized flow rate. The method robustness was checked by using a bifurcation sequential approach investigating the influence of 13 factors. The eluent recommended in the monograph is a ternary mixture of methanol, phosphate buffer and ethyl acetate. For the sake of simplicity, the phosphate buffer was substituted by an acetate buffer. The best composition of the ternary mixture was determined by a combined design including three mixture variables and the temperature as an independent variable. Chromatographic parameters were modelled in terms of analysis time, resolution and asymmetry. Desirability functions permit one to cope with these parameters and to determine the best compromise. The naphthodianthrones were separated on a conventional endcapped octadecyl silica gel column eluted by a ternary mobile phase at 40 °C in 10 min.
Keywords: HPLC; St John’s wort; Hypericum perforatum L.; Naphthodianthrones; Chemometric methodology
Optimization of the assay of naphthodianthrones in dry St John’s wort extract by reversed-phase liquid chromatography by Guilhem Pages; Michael Mazarin; Michelle Sergent; Roger Phan-Tan-Luu; Corinne Delaurent (pp. 716-723).
An optimization procedure for the reversed-phase liquid chromatography (RPLC) assay of naphthodianthrones in St John’s wort extract from the European Pharmacopoeia project is described. The results obtained from two screening designs showed that light exposure, recommended in the monograph as sample pretreatment, does not permit one to obtain a reproducible quantification of the main ingredients. Improvement of the method robustness implies the need to overcome the problem of light exposure, to subsequently quantify protonaphthodianthrones and to perform the separation on octadecyl (ODS)-bonded phase at optimized flow rate. The method robustness was checked by using a bifurcation sequential approach investigating the influence of 13 factors. The eluent recommended in the monograph is a ternary mixture of methanol, phosphate buffer and ethyl acetate. For the sake of simplicity, the phosphate buffer was substituted by an acetate buffer. The best composition of the ternary mixture was determined by a combined design including three mixture variables and the temperature as an independent variable. Chromatographic parameters were modelled in terms of analysis time, resolution and asymmetry. Desirability functions permit one to cope with these parameters and to determine the best compromise. The naphthodianthrones were separated on a conventional endcapped octadecyl silica gel column eluted by a ternary mobile phase at 40 °C in 10 min.
Keywords: HPLC; St John’s wort; Hypericum perforatum L.; Naphthodianthrones; Chemometric methodology
Application of a novel electrosynthesized polydopamine-imprinted film to the capacitive sensing of nicotine by Kai Liu; Wan-Zhi Wei; Jin-Xiang Zeng; Xiao-Ying Liu; Yan-Ping Gao (pp. 724-729).
The application of novel electrosynthesized polydopamine (PDA)-imprinted film as a recognition element for the capacitive sensing of nicotine is reported. The PDA-imprinted film was electropolymerized directly on the gold electrode surface in the presence of nicotine without an additional self-assembled thiol sublayer. The compact PDA film has various functional groups that aid the imprinting procedure. Furthermore, the film shows good capacitive response since it is insulating in nature and ultrathin. The sensor’s linear response range for nicotine was between 1–25 μmol L−1, with a detection limit of 0.5 μmol L−1. The proposed molecularly imprinted polymer capacitive (MIPC) sensor exhibited good selectivity for nicotine. The reproducibility and repeatability of the MIPC senor were all found to be satisfactory. The results from sample analysis confirmed the applicability of the MIPC sensor to quantitative analysis.
Keywords: Dopamine; Molecularly imprinted polymer; Electropolymerization; Capacitive sensing; Nicotine
Application of a novel electrosynthesized polydopamine-imprinted film to the capacitive sensing of nicotine by Kai Liu; Wan-Zhi Wei; Jin-Xiang Zeng; Xiao-Ying Liu; Yan-Ping Gao (pp. 724-729).
The application of novel electrosynthesized polydopamine (PDA)-imprinted film as a recognition element for the capacitive sensing of nicotine is reported. The PDA-imprinted film was electropolymerized directly on the gold electrode surface in the presence of nicotine without an additional self-assembled thiol sublayer. The compact PDA film has various functional groups that aid the imprinting procedure. Furthermore, the film shows good capacitive response since it is insulating in nature and ultrathin. The sensor’s linear response range for nicotine was between 1–25 μmol L−1, with a detection limit of 0.5 μmol L−1. The proposed molecularly imprinted polymer capacitive (MIPC) sensor exhibited good selectivity for nicotine. The reproducibility and repeatability of the MIPC senor were all found to be satisfactory. The results from sample analysis confirmed the applicability of the MIPC sensor to quantitative analysis.
Keywords: Dopamine; Molecularly imprinted polymer; Electropolymerization; Capacitive sensing; Nicotine
pH effect on dynamic coating for capillary electrophoresis of DNA by Sheng-Bing Yu; Ping Zhou; Ai-Rong Feng; Xin-Cheng Shen; Zhi-Ling Zhang; Ji-Ming Hu (pp. 730-736).
A buffer consisting of tris(hydroxymethyl)aminomethane, 2-(N-moropholino)ethanesulfonic acid (Mes) and EDTA with constant ion strength was used to investigate the effect of buffer pH on the dynamic coating behavior of poly(N-isopropylacrylamide) (PNIPAM) for DNA separation. The atomic force microscopy (AFM) image illustrated that PNIPAM in lower-pH buffer was much more efficient in covering a silica wafer than that in higher-pH buffer. The coating performance of PNIPAM was also quantitatively analyzed by Fourier transform IR attenuated total reflectance spectroscopy and by measuring the electroosmotic flow (EOF). These results indicated that the stability of the dynamic coating was dependent on the pH of the sieving matrix and was improved by reducing the pH to the weak-acid range. The lower pH of the sieving buffer may induce the polymer more efficiently to adsorb on the capillary wall to suppress EOF and DNA–capillary wall interaction for DNA separation. The enhanced dynamic coating capacity of PNIPAM in lower-pH buffer may be attributed to the hydrogen bonds between the hydroxyl groups of the silica surface and the oxygen atom of the carbonyl groups of PNIPAM.
Keywords: Capillary electrophoresis; pH; Dynamic coating; DNA separation; Poly-N-isopropylacrylamide
pH effect on dynamic coating for capillary electrophoresis of DNA by Sheng-Bing Yu; Ping Zhou; Ai-Rong Feng; Xin-Cheng Shen; Zhi-Ling Zhang; Ji-Ming Hu (pp. 730-736).
A buffer consisting of tris(hydroxymethyl)aminomethane, 2-(N-moropholino)ethanesulfonic acid (Mes) and EDTA with constant ion strength was used to investigate the effect of buffer pH on the dynamic coating behavior of poly(N-isopropylacrylamide) (PNIPAM) for DNA separation. The atomic force microscopy (AFM) image illustrated that PNIPAM in lower-pH buffer was much more efficient in covering a silica wafer than that in higher-pH buffer. The coating performance of PNIPAM was also quantitatively analyzed by Fourier transform IR attenuated total reflectance spectroscopy and by measuring the electroosmotic flow (EOF). These results indicated that the stability of the dynamic coating was dependent on the pH of the sieving matrix and was improved by reducing the pH to the weak-acid range. The lower pH of the sieving buffer may induce the polymer more efficiently to adsorb on the capillary wall to suppress EOF and DNA–capillary wall interaction for DNA separation. The enhanced dynamic coating capacity of PNIPAM in lower-pH buffer may be attributed to the hydrogen bonds between the hydroxyl groups of the silica surface and the oxygen atom of the carbonyl groups of PNIPAM.
Keywords: Capillary electrophoresis; pH; Dynamic coating; DNA separation; Poly-N-isopropylacrylamide
A sequential injection fluorometric procedure for the determination of procaine in human blood and pharmaceuticals by Xu-Wei Chen; Xin Song; Jian-Hua Wang (pp. 737-741).
An automated procedure for the assay of procaine hydrochloride in human blood and pharmaceuticals was developed using a sequential injection (SI) technique with fluorometric detection and fluorescamine as the fluorescence probe. A few microliters of fluorescamine and procaine hydrochloride solutions were used in the SI system leading to the formation of a derivative, which was then excited by a 400-nm LED and whose emitted fluorescence was monitored at a wavelength of 494 nm. A linear calibration graph was obtained with 10–200 ng mL−1 (procaine) by loading 10.0 μL of sample solution and 5.0 μL of fluorescamine solution (both 0.125 % m/v). A detection limit of 2.6 ng mL−1, defined as 3 times the blank standard deviation (3σ), was achieved along with a sampling frequency of 25 h−1 and a precision of 2.1 % RSD at the 50.0 ng mL−1 level. Procaine contents in injection solutions from various pharmaceutical manufactures were analyzed and reasonable agreement was achieved between the values obtained by using the present procedure and the documented spectrophotometry, and both were coincident with the nominal concentrations. In addition, the degradation of procaine in human blood was investigated. A fast degradation of procaine in human blood was observed for the first 30 min, while afterwards the degradation was retarded.
Keywords: Sequential injection; Fluorometry; Procaine degradation; Fluorecamine
A sequential injection fluorometric procedure for the determination of procaine in human blood and pharmaceuticals by Xu-Wei Chen; Xin Song; Jian-Hua Wang (pp. 737-741).
An automated procedure for the assay of procaine hydrochloride in human blood and pharmaceuticals was developed using a sequential injection (SI) technique with fluorometric detection and fluorescamine as the fluorescence probe. A few microliters of fluorescamine and procaine hydrochloride solutions were used in the SI system leading to the formation of a derivative, which was then excited by a 400-nm LED and whose emitted fluorescence was monitored at a wavelength of 494 nm. A linear calibration graph was obtained with 10–200 ng mL−1 (procaine) by loading 10.0 μL of sample solution and 5.0 μL of fluorescamine solution (both 0.125 % m/v). A detection limit of 2.6 ng mL−1, defined as 3 times the blank standard deviation (3σ), was achieved along with a sampling frequency of 25 h−1 and a precision of 2.1 % RSD at the 50.0 ng mL−1 level. Procaine contents in injection solutions from various pharmaceutical manufactures were analyzed and reasonable agreement was achieved between the values obtained by using the present procedure and the documented spectrophotometry, and both were coincident with the nominal concentrations. In addition, the degradation of procaine in human blood was investigated. A fast degradation of procaine in human blood was observed for the first 30 min, while afterwards the degradation was retarded.
Keywords: Sequential injection; Fluorometry; Procaine degradation; Fluorecamine
Analytical approach for monitoring endocrine-disrupting compounds in urban waste water treatment plants by Aldo Roda; Mara Mirasoli; Elisa Michelini; Maria Magliulo; Patrizia Simoni; Massimo Guardigli; Roberta Curini; Manuel Sergi; Alessandra Marino (pp. 742-752).
The presence of endocrine-disrupting compounds in influent and effluent water samples from four waste water treatment plants located in Italy was studied. The estrogen-like activity of the water samples was measured using a chemiluminescent recombinant yeast assay which is based on genetically engineered yeast cells that express the human estrogen receptor. This receptor, once activated, elicits the expression of the reporter gene lac-Z and, consequently, the production of β-galactosidase, which is then measured by chemiluminescence. To control and minimize sample matrix effects, an external control based on a modified yeast strain stably expressing β-galactosidase was developed and also used in the assay. Rapid and sensitive chemiluminescent enzyme immunoassays were also developed and validated for the quantification of 17β-estradiol, estrone, and estriol in waste water samples. Results from both methods were compared with a reference high-performance liquid chromatography and electrospray ionization tandem mass spectrometry (HPLC ESI-MS-MS) method developed for the quantification of natural estrogens. The recombinant yeast assay revealed a significant estrogenic activity in the influent samples, ranging from 80 to 400 pmol/L 17β-estradiol equivalents (EEQ), which was reduced by 70–95 % in the effluent samples. The yeast assay also showed a systematic 20–30 % overestimation of estrogenic activity relative to the HPLC ESI-MS-MS method, suggesting the presence of other compounds in the samples with estrogenic activity. The chemiluminescent enzyme immunoassays showed the presence of estrogens in the influent samples (mean concentrations: 350–450 pmol/L for estrone, 5–100 pmol/L for 17β-estradiol, 25–300 pmol/L for estriol), with significantly lower concentrations detected in the respective effluent samples. The waste water treatment was able to reduce natural estrogen concentrations by 40–95 %, although a high variability was observed. The enzyme immunoassay data correlated well with data obtained by the HPLC ESI-MS-MS method. Although the recombinant yeast assay represents a useful tool for a first-level screening of estrogenic activity due to its simplicity and high analytical throughput, sample matrix effects observed in waste water of industrial origin were found to strongly affect the yeast cells response, even when properly corrected for using the external control, thereby limiting its use to urban waste water. Its integration with chemiluminescent enzyme immunoassays would improve its performance by reducing false negative results, thereby enabling its use in extensive studies monitoring for the presence of endocrine-disrupting compounds in urban treatment plant effluents.
Keywords: Chemiluminescence; Endocrine disrupting compounds; Enzyme immunoassay; Estrogens; Recombinant yeast assay; Waste water treatment plants
Analytical approach for monitoring endocrine-disrupting compounds in urban waste water treatment plants by Aldo Roda; Mara Mirasoli; Elisa Michelini; Maria Magliulo; Patrizia Simoni; Massimo Guardigli; Roberta Curini; Manuel Sergi; Alessandra Marino (pp. 742-752).
The presence of endocrine-disrupting compounds in influent and effluent water samples from four waste water treatment plants located in Italy was studied. The estrogen-like activity of the water samples was measured using a chemiluminescent recombinant yeast assay which is based on genetically engineered yeast cells that express the human estrogen receptor. This receptor, once activated, elicits the expression of the reporter gene lac-Z and, consequently, the production of β-galactosidase, which is then measured by chemiluminescence. To control and minimize sample matrix effects, an external control based on a modified yeast strain stably expressing β-galactosidase was developed and also used in the assay. Rapid and sensitive chemiluminescent enzyme immunoassays were also developed and validated for the quantification of 17β-estradiol, estrone, and estriol in waste water samples. Results from both methods were compared with a reference high-performance liquid chromatography and electrospray ionization tandem mass spectrometry (HPLC ESI-MS-MS) method developed for the quantification of natural estrogens. The recombinant yeast assay revealed a significant estrogenic activity in the influent samples, ranging from 80 to 400 pmol/L 17β-estradiol equivalents (EEQ), which was reduced by 70–95 % in the effluent samples. The yeast assay also showed a systematic 20–30 % overestimation of estrogenic activity relative to the HPLC ESI-MS-MS method, suggesting the presence of other compounds in the samples with estrogenic activity. The chemiluminescent enzyme immunoassays showed the presence of estrogens in the influent samples (mean concentrations: 350–450 pmol/L for estrone, 5–100 pmol/L for 17β-estradiol, 25–300 pmol/L for estriol), with significantly lower concentrations detected in the respective effluent samples. The waste water treatment was able to reduce natural estrogen concentrations by 40–95 %, although a high variability was observed. The enzyme immunoassay data correlated well with data obtained by the HPLC ESI-MS-MS method. Although the recombinant yeast assay represents a useful tool for a first-level screening of estrogenic activity due to its simplicity and high analytical throughput, sample matrix effects observed in waste water of industrial origin were found to strongly affect the yeast cells response, even when properly corrected for using the external control, thereby limiting its use to urban waste water. Its integration with chemiluminescent enzyme immunoassays would improve its performance by reducing false negative results, thereby enabling its use in extensive studies monitoring for the presence of endocrine-disrupting compounds in urban treatment plant effluents.
Keywords: Chemiluminescence; Endocrine disrupting compounds; Enzyme immunoassay; Estrogens; Recombinant yeast assay; Waste water treatment plants
Multivariate optimisation of the microwave-assisted extraction of oleuropein and related biophenols from olive leaves by R. Japón-Luján; J. M. Luque-Rodríguez; M. D. Luque de Castro (pp. 753-759).
Microwave assistance is proposed for the first time in order to accelerate the extraction of biophenols from olive leaves. Under optimal working conditions, obtained using a multivariate methodology, complete extraction of the target analytes was achieved in 8 min. The extracts required no clean-up nor concentration prior to injection into a chromatograph–photodiode array detector assembly for individual separation–quantification. The optimal extractant (an 80:20 ethanol–water mixture) was also used in the development of a stirring-based extraction method which required around 24 h for complete extraction of the target compounds. These mixtures can be used as replacements for toxic extractants, with a view to exploiting olive leaves in order to obtain biophenols for human use.
Keywords: Microwave-assisted extraction; Oleuropein; Biophenols; Polyphenols; OBPs; Olive leaves
Multivariate optimisation of the microwave-assisted extraction of oleuropein and related biophenols from olive leaves by R. Japón-Luján; J. M. Luque-Rodríguez; M. D. Luque de Castro (pp. 753-759).
Microwave assistance is proposed for the first time in order to accelerate the extraction of biophenols from olive leaves. Under optimal working conditions, obtained using a multivariate methodology, complete extraction of the target analytes was achieved in 8 min. The extracts required no clean-up nor concentration prior to injection into a chromatograph–photodiode array detector assembly for individual separation–quantification. The optimal extractant (an 80:20 ethanol–water mixture) was also used in the development of a stirring-based extraction method which required around 24 h for complete extraction of the target compounds. These mixtures can be used as replacements for toxic extractants, with a view to exploiting olive leaves in order to obtain biophenols for human use.
Keywords: Microwave-assisted extraction; Oleuropein; Biophenols; Polyphenols; OBPs; Olive leaves
Purity assessment problem in quantitative NMR—impurity resonance overlaps with monitor signal multiplets from stereoisomers by Frank Malz; Harald Jancke (pp. 760-765).
This paper describes the situation that can emerge when the signals to be evaluated in quantitative NMR measurements—so-called “monitor signals”—consist of several resonance lines from the stereoisomers of the analyte in addition to an impurity signal underneath. The monitor signal problem is demonstrated in the purity assessment of two samples of 2-(isopropylamino)-4-(ethylamino)-6-chloro-1,3,5-triazine (atrazine), a common herbizide which served as analyte in a CCQM intercomparison. It is shown that, in DMSO-d6 solution, a mixture of stereoisomers leads to several individual overlapping singlets, which are further split by spin–spin coupling. A measurement protocol was developed for finding and identifying an impurity that has a signal that is positioned precisely beneath the methyl signal chosen as the monitor signal in one of the samples. Quantitative NMR purity assessment is still possible in this special case, but with higher uncertainty.
Keywords: Quantitative NMR; Monitor signal; Impurities; Atrazine; Purity assessment
Purity assessment problem in quantitative NMR—impurity resonance overlaps with monitor signal multiplets from stereoisomers by Frank Malz; Harald Jancke (pp. 760-765).
This paper describes the situation that can emerge when the signals to be evaluated in quantitative NMR measurements—so-called “monitor signals”—consist of several resonance lines from the stereoisomers of the analyte in addition to an impurity signal underneath. The monitor signal problem is demonstrated in the purity assessment of two samples of 2-(isopropylamino)-4-(ethylamino)-6-chloro-1,3,5-triazine (atrazine), a common herbizide which served as analyte in a CCQM intercomparison. It is shown that, in DMSO-d6 solution, a mixture of stereoisomers leads to several individual overlapping singlets, which are further split by spin–spin coupling. A measurement protocol was developed for finding and identifying an impurity that has a signal that is positioned precisely beneath the methyl signal chosen as the monitor signal in one of the samples. Quantitative NMR purity assessment is still possible in this special case, but with higher uncertainty.
Keywords: Quantitative NMR; Monitor signal; Impurities; Atrazine; Purity assessment
Partial least-squares near-infrared determination of hydrocarbons removed from polluted waters by using tanned solid wastes by A. Gammoun; J. Moros; S. Tahiri; S. Garrigues; M. de la Guardia (pp. 766-770).
A new procedure has been developed for the determination of hydrocarbons retained in solid tanned wastes from polluted waters. The method uses near-infrared (NIR) transmission spectra obtained from leachates of the hydrocarbons with CCl4 using a partial least-squares (PLS) calibration model based on the use of mixtures of n-hexane, isooctane, and toluene diluted with CCl4. This methodology was applied to the evaluation of the absorption capacity of chrome shavings in water samples polluted with hydrocarbons, resulting in a maximum absorption capacity of 6.30 g hydrocarbons per g solid waste.
Keywords: Hydrocarbons; Isooctane; Toluene; n-Hexane; Tannery solid wastes; NIR determination; PLS
Partial least-squares near-infrared determination of hydrocarbons removed from polluted waters by using tanned solid wastes by A. Gammoun; J. Moros; S. Tahiri; S. Garrigues; M. de la Guardia (pp. 766-770).
A new procedure has been developed for the determination of hydrocarbons retained in solid tanned wastes from polluted waters. The method uses near-infrared (NIR) transmission spectra obtained from leachates of the hydrocarbons with CCl4 using a partial least-squares (PLS) calibration model based on the use of mixtures of n-hexane, isooctane, and toluene diluted with CCl4. This methodology was applied to the evaluation of the absorption capacity of chrome shavings in water samples polluted with hydrocarbons, resulting in a maximum absorption capacity of 6.30 g hydrocarbons per g solid waste.
Keywords: Hydrocarbons; Isooctane; Toluene; n-Hexane; Tannery solid wastes; NIR determination; PLS
Chemometric analysis of soil pollution data using the Tucker N-way method by I. Stanimirova; K. Zehl; D. L. Massart; Y. Vander Heyden; J. W. Einax (pp. 771-779).
N-way methods, particularly the Tucker method, are often the methods of choice when analyzing data sets arranged in three- (or higher) way arrays, which is the case for most environmental data sets. In the future, applying N-way methods will become an increasingly popular way to uncover hidden information in complex data sets. The reason for this is that classical two-way approaches such as principal component analysis are not as good at revealing the complex relationships present in data sets. This study describes in detail the application of a chemometric N-way approach, namely the Tucker method, in order to evaluate the level of pollution in soil from a contaminated site. The analyzed soil data set was five-way in nature. The samples were collected at different depths (way 1) from two locations (way 2) and the levels of thirteen metals (way 3) were analyzed using a four-step-sequential extraction procedure (way 4), allowing detailed information to be obtained about the bioavailability and activity of the different binding forms of the metals. Furthermore, the measurements were performed under two conditions (way 5), inert and non-inert. The preferred Tucker model of definite complexity showed that there was no significant difference in measurements analyzed under inert or non-inert conditions. It also allowed two depth horizons, characterized by different accumulation pathways, to be distinguished, and it allowed the relationships between chemical elements and their biological activities and mobilities in the soil to be described in detail.
Keywords: Chemometrics; Heavy metal pollution; Tucker; Sequential extraction; Soil
Chemometric analysis of soil pollution data using the Tucker N-way method by I. Stanimirova; K. Zehl; D. L. Massart; Y. Vander Heyden; J. W. Einax (pp. 771-779).
N-way methods, particularly the Tucker method, are often the methods of choice when analyzing data sets arranged in three- (or higher) way arrays, which is the case for most environmental data sets. In the future, applying N-way methods will become an increasingly popular way to uncover hidden information in complex data sets. The reason for this is that classical two-way approaches such as principal component analysis are not as good at revealing the complex relationships present in data sets. This study describes in detail the application of a chemometric N-way approach, namely the Tucker method, in order to evaluate the level of pollution in soil from a contaminated site. The analyzed soil data set was five-way in nature. The samples were collected at different depths (way 1) from two locations (way 2) and the levels of thirteen metals (way 3) were analyzed using a four-step-sequential extraction procedure (way 4), allowing detailed information to be obtained about the bioavailability and activity of the different binding forms of the metals. Furthermore, the measurements were performed under two conditions (way 5), inert and non-inert. The preferred Tucker model of definite complexity showed that there was no significant difference in measurements analyzed under inert or non-inert conditions. It also allowed two depth horizons, characterized by different accumulation pathways, to be distinguished, and it allowed the relationships between chemical elements and their biological activities and mobilities in the soil to be described in detail.
Keywords: Chemometrics; Heavy metal pollution; Tucker; Sequential extraction; Soil
Selective solid-phase extraction of bisphenol A using molecularly imprinted polymers and its application to biological and environmental samples by Jiang-hua Zhang; Ming Jiang; Lijun Zou; Dan Shi; Su-rong Mei; Ye-xiang Zhu; Yun Shi; Kang Dai; Bin Lu (pp. 780-786).
Molecularly imprinted polymers (MIPs) were prepared using bisphenol A (BPA) as a template by precipitation polymerization. The polymer that had the highest binding selectivity and ability was used as solid-phase extraction (SPE) sorbents for direct extraction of BPA from different biological and environmental samples (human serum, pig urine, tap water and shrimp). The extraction protocol was optimized and the optimum conditions were as follows: conditioning with 5 mL methanol–acetic acid (3:1), 5 mL methanol, 5 mL acetonitrile and 5 mL water, respectively, loading with 5 mL aqueous samples, washing with 1 mL acetonitrile, and eluting with 3 mL methanol. MIPs can selectively recognize, effectively trap and preconcentrate BPA over a concentration range of 2–20 μM. Recoveries ranged from 94.03 to 105.3 %, with a relative standard deviation lower than 7.9 %. Under the optimal condition, molecularly imprinted SPE recoveries of spiked human serum, pig urine, tap water and shrimp were 65.80, 82.32, 76.00 and 75.97 %, respectively, when aqueous samples were applied directly. Compared with C18 SPE, a better baseline, better high-performance liquid chromatography separation efficiency and higher recoveries were achieved after molecularly imprinted SPE.
Keywords: Molecularly imprinted polymers; Solid-phase extraction; Bisphenol A; Biological and environmental samples
Selective solid-phase extraction of bisphenol A using molecularly imprinted polymers and its application to biological and environmental samples by Jiang-hua Zhang; Ming Jiang; Lijun Zou; Dan Shi; Su-rong Mei; Ye-xiang Zhu; Yun Shi; Kang Dai; Bin Lu (pp. 780-786).
Molecularly imprinted polymers (MIPs) were prepared using bisphenol A (BPA) as a template by precipitation polymerization. The polymer that had the highest binding selectivity and ability was used as solid-phase extraction (SPE) sorbents for direct extraction of BPA from different biological and environmental samples (human serum, pig urine, tap water and shrimp). The extraction protocol was optimized and the optimum conditions were as follows: conditioning with 5 mL methanol–acetic acid (3:1), 5 mL methanol, 5 mL acetonitrile and 5 mL water, respectively, loading with 5 mL aqueous samples, washing with 1 mL acetonitrile, and eluting with 3 mL methanol. MIPs can selectively recognize, effectively trap and preconcentrate BPA over a concentration range of 2–20 μM. Recoveries ranged from 94.03 to 105.3 %, with a relative standard deviation lower than 7.9 %. Under the optimal condition, molecularly imprinted SPE recoveries of spiked human serum, pig urine, tap water and shrimp were 65.80, 82.32, 76.00 and 75.97 %, respectively, when aqueous samples were applied directly. Compared with C18 SPE, a better baseline, better high-performance liquid chromatography separation efficiency and higher recoveries were achieved after molecularly imprinted SPE.
Keywords: Molecularly imprinted polymers; Solid-phase extraction; Bisphenol A; Biological and environmental samples