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Biomedical subjects

S Chiron

Publications and source records attributed to S Chiron.

9 recordsLinked to original sources
PubMed2000

Speciation of butyl- and phenyltin compounds in sediments using pressurized liquid extraction and liquid chromatography-inductively coupled plasma mass spectrometry.

A liquid chromatographic method with inductively coupled plasma mass spectrometry is proposed for the speciation of butyl- (monobutyltin, dibutyltin, tributyltin) and phenyl- (monophenyltin, diphenyltin, triphenyltin) tin compounds in sediments. After evaluation of different additives in the mobile phase, the use of 0.075% (w/v) of tropolone and 0.1% (v/v) of triethylamine in a mobile phase of methanol-acetic acid-water (72.5:6:21.5) allowed the best chromatographic separation of the six compounds. Pressurized liquid extraction (PLE) with a methanolic mixture of 0.5 M acetic acid and 0.2% (w/v) of tropolone was suitable for the quantitative extraction of butyl- and phenyltin compounds with recovery values ranging from 72 to 102%. This analytical approach was compared to conventional solvent extraction methods making use of acids and/or organic solvent of medium polarity. The main advantages of PLE over conventional solvent extraction are: (i) the possibility to extract quantitatively DPhT and MPhT from sediments, which could not be done by a solvent extraction approach; (ii) to preserve the structural integrity of the organotin compounds; (iii) to reduce the extraction time from several hours in case of solvent extraction techniques to just 30 min. For spiked sediments, limits of detection ranged from 0.7 to 2 ng/g of tin according to the compound. The relative standard deviations were found to be between 8 and 15%. The developed analytical procedure was validated using a reference material and was applied to various environmental samples.

Chromatography, High Pressure Liquid↗
PubMed1998

Application of gas and liquid chromatography-mass spectrometry to the evaluation of pirimiphos methyl degradation products in industrial water under ozone treatment.

The organophosphorus compound pirimiphos methyl was oxidized in water under ozonolysis in the presence of formulating agents. A rapid sample handling procedure was developed based on liquid-solid extraction with nonporous carbon cartridges. This sorbent material allowed recovery of the polar degradation products (DPs). Analysis of oxidized solutions was performed with both GC-ion trap (IT)-MS using either electron impact or chemical ionization as ionization modes and LC-atmospheric pressure ionization (API)-MS using either an ionspray (ISP) or an atmospheric pressure chemical ionization (APCI) interface in order to confirm the presence of DPs. The performances of both technologies were evaluated for structure elucidation and quantitation by using pirimiphos methyl, 2,4-aminophenol and cyanuric acid as external standards of DPs. LC-API-MS techniques allowed the detection of six DPs, of which two were not detected by GC-IT-MS techniques, even after a derivatization procedure with BF3-MeOH reagent. ISP was the most suitable ionization method for identifying the DPs, because sodium or potassium adduct ions were of great help in confirming the molecular mass of unknowns. APCI provided more fragmentation patterns than ISP. However unequivocal identification of all DPs was impossible and only a tentative degradation pathway of pirimiphos methyl in water under ozone is proposed. At the end of the reaction time, DPs accounted for between 70 and 85% of the initial concentration of methyl pirimiphos.

Chromatography, Liquid↗
PubMed1996

Determination of imidacloprid in vegetables by high-performance liquid chromatography with diode-array detection.

An HPLC method is described for the determination of imidacloprid residues in vegetables at levels ranging from 0.01 to 0.60 mg/kg. The selection of the extraction and clean-up procedure is discussed. Spectral data obtained with diode-array detection allow the identification of imidacloprid residues. Thermospray mass spectrometric studies were carried out in combination with HPLC. The mean recoveries and standard deviations were 95% and 4.7%, respectively, in the various crops tested. Registration of the analytical results for a control sample in quality control charts demonstrated the performance of the method. Data for incurred residues of imidacloprid in vegetable samples routinely applying the proposed method are also presented.

Chromatography, High Pressure Liquid↗
PubMed1993

Determination of pesticides in drinking water by on-line solid-phase disk extraction followed by various liquid chromatographic systems.

C-18 Empore extraction disks were coupled on-line with liquid chromatography-rapid scanning UV-VIS detection and post-column fluorescence detection for the isolation and trace enrichment of various pesticides [carbamates, (aldicarb, carbofuran, carbaryl), carbamate transformation products (TPs) (aldicarb sulfoxide, aldicarb sulfone, 3-hydroxycarbofuran, 3-hydroxy-7-phenol carbofuran, 3-keto-carbofuranphenol and 3-ketocarbofuran) and herbicides (chlortoluron, isoproturon and metolachlor)] spiked at concentration levels of 0.2 and 5 micrograms/l in drinking water samples. Recoveries were dependent on the pesticide level and preconcentrated water volume (50 ml to 1000 ml) using LC with rapid scanning UV-VIS detection. The same on-line system coupled with LC-post-column derivatization fluorescence detection has needed only 10 ml of water to achieve similar levels of determination for the carbamate insecticides.

Carbamates↗
PubMedDate not supplied

Automated sample preparation for monitoring groundwater pollution by carbamate insecticides and their transformation products.

We investigated automated on-line solid-phase extraction (SPE) followed by liquid chromatographic (LC) techniques for monitoring carbamates and their transformation products. Analytical determinations were performed by LC with UV or postcolumn fluorescence detection (U.S. Environmental Protection Agency Method 531.1 for carbamate insecticides) after preconcentration with on-line SPE using C18 Empore extraction disks. On-line SPE/LC/thermospray mass spectrometry with time-scheduled selected-ion monitoring was used as confirmatory method. The method was used to determine pesticide traces in well waters of a typical aquifer in the Almeria area (Andalucia, south of Spain) from March 1993 to February 1994. The major pollutants, found in highest amounts, were carbofuran, methiocarb, and methomyl, at levels of 0.32, 0.3, and 0.8 micrograms/L, respectively. According to results of seasonal variation studies, pollution by carbamate insecticides is sporadic and exceeds the limit of 0.5 micrograms/L for total pesticides allowed by the European Economic Community Drinking Water Directive only twice a year. 3-Hydroxycarbofuran and methiocarb sulfone also were detected, showing the importance of including the main toxic break-down products of carbamate insecticides in future monitoring programs.

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