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Analytica Chimica Acta (v.608, #1)
Monitoring of environmental pollutants by bioluminescent bacteria by Stefano Girotti /; Elida Nora Ferri; Maria Grazia Fumo; Elisabetta Maiolini (pp. 2-29).
This review deals with the applications of bioluminescent bacteria to the environmental analyses, published during the years 2000–2007. The ecotoxicological assessment, by bioassays, of the environmental risks and the luminescent approaches are reported. The review includes a brief introduction to the characteristics and applications of bioassays, a description of the characteristics and applications of natural bioluminescent bacteria (BLB), and a collection of the main applications to organic and inorganic pollutants. The light-emitting genetically modified bacteria applications, as well as the bioluminescent immobilized systems and biosensors are outlined. Considerations about commercially available BLB and BLB catalogues are also reported. Most of the environmental applications, here mentioned, of luminescent organisms are on wastewater, seawater, surface and ground water, tap water, soil and sediments, air. Comparison to other bioindicators and bioassay has been also made. Various tables have been inserted, to make easier to take a rapid glance at all possible references concerning the topic of specific interest.
Keywords: Environmental pollutants; Bioluminescent bacteria; Water; Soil; Genetically modified bacteria; Biotoxicity assays
Determination of monomethylmercury in low- and high-polluted sediments by microwave extraction and gas chromatography with atomic fluorescence detection by J.J. Berzas Nevado; R.C. Rodríguez Martín-Doimeadios; F.J. Guzmán Bernardo; M. Jiménez Moreno (pp. 30-37).
The analysis of monomethylmercury (MMHg) in sediments is a difficult task because both very low concentrations and interconversion between species especially in highly polluted samples are frequent. This work features a general strategy for real sediment analysis with preconcentration and/or clean-up steps for both low- and high-polluted sediments to control these specific problems. The extraction conditions have been optimized using closed-vessel microwave-assisted heating with acidic extractants. The analysis has been carried out by the injection of ethylated derivatives of the analytes into a capillary gas chromatographic system coupled to fluorescence spectrometry. When using 6M HNO3, the most labile inorganic mercury fraction as well as MMHg were extracted from the sediment but there was still some inorganic mercury that remained un-extracted. MMHg was stable and quantitatively recovered by applying this procedure. The role of the labile inorganic fraction on artifact MMHg generation has been evaluated and it has been found to be highly variable depending on the sediments’ geochemical characteristics. Therefore, for high-polluted sediments (inorganic mercury concentration above 500ngg−1) a clean-up step with dichloromethane has been used before ethylation, whereas for low content samples, preconcentration under nitrogen stream at room temperature has been optimized. Both steps can be combined if necessary. MMHg content has been found in good agreement with the certified value for the reference materials (IAEA-405 and ERM-CC580).
Keywords: Mercury speciation; Artifact formation; Closed-vessel microwave-assisted extraction; Gas chromatography; Atomic fluorescence spectrometry
Vinegar classification based on feature extraction and selection from headspace solid-phase microextraction/gas chromatography volatile analyses: A feasibility study by C. Pizarro; I. Esteban-Díez; C. Sáenz-González; J.M. González-Sáiz (pp. 38-47).
Headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography (GC) and multivariate data analysis were applied to classify different vinegar types (white and red, balsamic, sherry and cider vinegars) on the basis of their volatile composition. The collected chromatographic signals were analysed using the stepwise linear discriminant analysis (SLDA) method, thus simultaneously performing feature selection and classification. Several options, more or less restrictive according to the final number of considered categories, were explored in order to identify the one that afforded highest discrimination ability. The simplicity and effectiveness of the classification methodology proposed in the present study (all the samples were correctly classified and predicted by cross-validation) are promising and encourage the feasibility of using a similar strategy to evaluate the quality and origin of vinegar samples in a reliable, fast, reproducible and cost-efficient way in routine applications. The high quality results obtained were even more remarkable considering the reduced number of discriminant variables finally selected by the stepwise procedure. The use of only 14 peaks enabled differentiation between cider, balsamic, sherry and wine vinegars, whereas only 3 variables were selected to discriminate between red (RW) and white wine (WW) vinegars. The subsequent identification by gas chromatography–mass spectrometry (GC–MS) of the volatile compounds associated with the discriminant peaks selected in the classification process served to interpret their chemical significance.
Keywords: Headspace solid-phase microextraction (HS-SPME); Gas chromatography–mass spectrometry (GC–MS); Vinegar; Volatile compounds; Feature selection; Stepwise linear discriminant analysis
A combination of spectral re-alignment and BTEM for the estimation of pure component NMR spectra from multi-component non-reactive and reactive systems by Liangfeng Guo; Peter Sprenger; Marc Garland (pp. 48-55).
The deconvolution of multi-component mixtures in NMR spectroscopy is a challenging problem due to the spectral non-linearities. In the present contribution, two data sets were studied (A) 10 samples of a four-component non-reactive mixture measured with1H,13C,19F,31P NMR and (B) a three-solute cyclo-addition reaction measured with13C NMR. Both data sets were treated with a re-alignment procedure to correct for the non-stationary chemical shifts, followed by band-target entropy minimization (BTEM) analysis. For data set A, quite good spectral estimates of the two hydrogen-containing species, four carbon-containing species, two fluorine-containing species and two phosphorus-containing species were obtained from the multi-component data. For data set B quite good spectral estimates of all three carbon-containing reactants were obtained as well as their relative concentration profiles. The present contribution using model systems indicates the usefulness of re-alignment procedures for correcting non-stationary characteristics, prior to self-modeling curve resolution (SMCR), and the potential for investigating more complex problems.
Keywords: Band-target entropy minimization; Non-stationary signals; Chemical shift; Mixture analysis; Chemometrics
Electrochemical detection of triacetone triperoxide employing the electrocatalytic reaction of iron(II/III)-ethylenediaminetetraacetate and hydrogen peroxide by Derek F. Laine; Christopher W. Roske; I. Francis Cheng (pp. 56-60).
An electrochemical method for the detection of triacetone triperoxide (TATP) is proposed and examined. In this method, TATP solutions were treated with 1.08M HCl for 10min releasing H2O2 and/or hydroperoxides. Subsequently, these peroxides undergo an electrocatalytic reduction through the FeII/IIIethylenediaminetetraacetate (EDTA) complex at a glassy carbon electrode. Cyclic voltammetric results indicate that no redox reaction was observed between FeIIEDTA and TATP. Acid treated TATP yielded voltammograms indicative of electrocatalysis of ROOH/HOOH reduction via FeII/IIIEDTA redox cycling. Chronoamperometric results yielded a detection limit of 0.89μM for TATP and a sensitivity of 0.025mAmM−1. The influence of pH and O2 interference on the analytical signal is briefly discussed.
Keywords: Triacetone triperoxide; Electrocatalytic; Detection; Iron(III)-ethylenediaminetetraacetate
Multifunctional sorbents for the extraction of pesticide multiresidues from natural waters by Antonia Moral; María Dolores Sicilia; Soledad Rubio; Dolores Pérez-Bendito (pp. 61-72).
In this work multifunctional sorbents, based on surfactant-coated mineral oxides, are assessed for the simultaneous extraction/preconcentration of pesticide multiresidues from aqueous environmental samples. Seventeen pesticides, representative of all the common groups (triazines, phenylureas, carbamates, azols, anilides, chloroacetanilides, organophosphorous, phenoxyacids, aryloxy acids and phenols), are selected for this study. The sorbents assessed are pure sodium dodecyl sulphate (SDS) and mixed tetrabutylammonium (TBA)–SDS hemimicelles and/or admicelles adsorbed onto alumina. Because of their multifunctional character, these sorbents provide different retention mechanisms (i.e. hydrophobic, ionic and/or π-cation interactions), which highly contribute to the efficient retention of pesticides with different polarities and acidities (bases, neutrals and acids). In addition, the low volume of eluent required for complete elution of analytes (typically 1–2mL) avoided the need of using time-consuming and tedious evaporation steps that generally are needed when cross-linked polymeric resins or carbon materials are used as sorbents. The performance of two sorbents, i.e. SDS and TBA–SDS mixed hemimicelles/admicelles, for the admicellar solid-phase extraction (ASPE) of pesticide multiresidue was comparatively investigated. The latter was selected on the basis of the higher breakthrough volumes permitted, the lower volume of eluent required and the higher sample and eluent flow rates allowed. The proposed ASPE/LC/UV approach provided detection limits lower than 100ngL−1 for the determination of the 17 pesticides tested. Recoveries from spiked (at the ngL−1 level) river and underground water samples was quantitative for most of the pesticides tested.
Keywords: Sodium dodecyl sulphate-coated alumina; Multifunctional sorbent; Admicellar solid-phase extraction; Liquid chromatography/ultraviolet spectrometry; Pesticide multiresidue determination; Natural waters
Rapid probing of photocatalytic activity on titania-based self-cleaning materials using 7-hydroxycoumarin fluorescent probe by Huimin Guan; Lihua Zhu; Hehui Zhou; Heqing Tang (pp. 73-78).
Self-cleaning materials are widely applied, but the available methods for determining their photocatalytic activity are time consuming. A simple analysis method was proposed to evaluate rapidly the photocatalytic activity of self-cleaning materials. This method is based on monitoring of a highly fluorescent product generated by the self-cleaning materials after illumination. Under UV irradiation, holes photo-induced on the surface of self-cleaning materials can oxidize water molecules (or hydroxide ions) adsorbed on the surface to produce hydroxyl radicals, which then quantitatively oxidize coumarin to highly fluorescent 7-hydroxycoumarin. It was observed that the fluorescence intensity of photo-generated 7-hydroxycoumarin at 456nm (excited at 346nm) linearly increased with irradiation time, and the fluorescence intensity at a given irradiation time was linearly proportional to the photocatalytic activity of self-cleaning materials. Consequently, the photocatalytic activity of self-cleaning materials was able to be probed simply by using this new method, which requires an analysis time of 40min, being much less than 250min required for a dye method.
Keywords: Fluorescent probe; Coumarin; Self-cleaning materials; Titania; Photocatalysis
2D Bitmapping approach for identification and quantitation of common base flavor adulterants using surface acoustic wave arrays and artificial neural network data analysis by Robert M. Sobel; David S. Ballantine (pp. 79-85).
Arrays of polymer-coated surface acoustic wave microsensors are used in conjunction with a variety of signal-processing algorithms known as artificial neural networks (ANN). This format of data analysis has the capability to characterize complex mixtures of volatile and semi-volatile organic compounds commonly found in base flavors. The approach described, which minimizes the number of training sets while retaining the robustness of an ANN, utilizes a 2D bitmap matrix. The matrix is obtained by converting the time domain kinetics of sensor response into a bitmap. The high data throughput of this approach enables quantitation on the order of ppm of common base flavor adulterants.
Keywords: Surface acoustic wave (SAW) sensor array; Artificial neural networks (ANN); Flavors analysis; Kinetics profile
ELISA for semicarbazide and its application for screening in food contamination by M. Vass; I. Diblikova; I. Cernoch; M. Franek (pp. 86-94).
The development of a direct competitive enzyme-linked immunosorbent assay (ELISA) based on polyclonal antibodies specific for semicarbazide (SEM) is described. Molecular modelling of the hapten mimics and other key components of the assay system was conducted to explain antibody properties in relation to hapten design. The small aliphatic molecule SEM was coupled to 3-carboxybenzaldehyde to produce carboxyphenyl-SEM (CPSEM), for the generation of specific antibodies. Five rabbits produced antibodies against NPSEM (used in direct and indirect ELISA formats) exhibiting a 50% binding inhibition level (IC50 values) of 0.06–2.28μgL−1 in assay buffer for SEM. The most sensitive indirect assay based on the antibody MVK39 showed a high dynamic range providing a linear readout in the range of 0.01–0.2μgL−1. Antibody MVK31 (IgG) allowed specific SEM detection at an IC50=0.14μgL−1 in direct ELISA and was evaluated using solvent extracted SEM-spiked porcine and baby food samples. Recovery levels determined from fortified samples (0.5, 1.0, 1.5, 5, 10 and 20μgkg−1) of porcine and baby food ranged from 82.9 to 105.3%, respectively, with a coefficient of variation less than 15.5%. Respective detection capability and threshold of the assay for porcine muscle, set on the basis of acceptance of no false negative results, was 0.3 and 0.11μgkg−1.
Keywords: Nitrofurans; Hapten design; Molecular modelling; Antibody characteristics; Semicarbazide; Enzyme-linked immunosorbent assay screening; Porcine; Baby food
Development of an on-site screening system for amphetamine-type stimulant tablets with a portable attenuated total reflection Fourier transform infrared spectrometer by Kenji Tsujikawa; Kenji Kuwayama; Hajime Miyaguchi; Tatsuyuki Kanamori; Yuko T. Iwata; Takemi Yoshida; Hiroyuki Inoue (pp. 95-103).
We tried to develop a library search system using a portable, attenuated total reflection Fourier transform infrared (ATR-FT-IR) spectrometer for on-site identification of 3,4-methylenedioxymethamphetamine (MDMA) and 3,4-methylenedioxyamphetamine (MDA) tablets. The library consisted of the spectra from mixtures of controlled drugs (e.g. MDMA and ketamine), adulterants (e.g. caffeine), and diluents (e.g. lactose). In the seven library search algorithms, the derivative correlation coefficient showed the best discriminant capability. This was enhanced by segmentation of the search area. The optimized search algorithm was validated by the positive ( n=154, e.g. the standard mixtures containing the controlled drug, and the MDMA/MDA tablets confiscated) and negative samples ( n=56, e.g. medicinal tablets). All validation samples except for four were judged truly. Final criteria for positive identification were decided on the basis of the results of the validation. In conclusion, a portable ATR-FT-IR spectrometer with our library search system would be a useful tool for on-site identification of amphetamine-type stimulant tablets.
Keywords: 3,4-Methylenedioxymethamphetamine; Attenuated total reflection Fourier transform infrared spectrometer; Library search; On-site identification; Tablet