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Flame Photometric Detection (flame + photometric_detection)
Selected AbstractsApplication of programmable temperature vaporisation injection with resistive heating-gas chromatography flame photometric detection for the determination of organophosphorus pesticidesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 1 2006Katan Patel Abstract The combination of a programmable temperature vaporisation (PTV) injector with resistive heating GC (RH-GC), a form of fast GC, has been applied to the analysis of organophosphorus (OP) pesticides. The PTV injector was optimised in the ,at-once' solvent vent mode for the injection of ethyl acetate (10,40 ,L) or ACN (10 ,L). The short RH-GC column (5 m×0.25 mm ID) with fast temperature ramps (up to 153°C/min) allowed the separation of a total of 20 OP pesticides in less than 6 min. Average recoveries between 67 and 119% were obtained for pesticides spiked at 0.01 mg/kg into apple and pear matrix. Extraction of orange juice with ACN provided higher recoveries (92,104%) for methamidophos, acephate and omethoate compared to ethyl acetate (62,73%). Results for analysis of OP pesticides in samples containing incurred residues were in good agreement with those obtained using GC-MS. The overall method was rapid, allowing 20 samples to be analysed in 4 h. British Crown Copyright © 2005 Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim [source] Modified headspace-SPME-GC device for sampling volatile compounds in acidic mediumJOURNAL OF SEPARATION SCIENCE, JSS, Issue 6-7 2003W. A. Araújo Abstract Most of the existing analytical methods for determining dithiocarbamate pesticide residues utilize an acid decomposition step, which promotes the release of carbon disulfide from the pesticide molecule. After release, the CS2 is sampled by static headspace techniques using gas-tight syringes and analyzed by gas chromatography with flame photometric detection (GC-FPD). In our search for faster analytical methodologies for sampling of volatile compounds we have used solid phase microextraction (SPME). However, evaluation of the commercially available SPME system for the analysis of CS2 obtained by decomposing dithiocarbamates showed it to be unsuitable for analysis in an acidic environment. The present communication reports the development of an appropriate device for sampling volatile compounds in an acidic environment by static headspace-SPME followed by GC-FPD. On examining the limitations of using a standard metal needle in HS-SPME sampling of analytes in acidic medium, a corrosion process was observed in both needle and fiber. A new double-needle device which avoids such corrosion problems was developed and built. The successful application of this device to the analysis of mancozeb in water samples is described. [source] Emission to air of volatile organotins from tributyltin-contaminated harbour sedimentsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 5 2002Alfred J. Vella Abstract An analytical method for determining the presence in air of volatile forms (e.g. chlorides) of tributyltin (TBT) and that of methylbutyltins MenBu(4,n)Sn (n,=,1,3) was developed and used to establish whether dredged harbour sediments contaminated with TBT served as sources of air pollution with respect to organotin compounds. The method was based on active sampling of the air being analysed and sorption of analytes onto Poropak-N. Sorbed methylbutyltins were extracted with dichloromethane and analysed by gas chromatography using flame photometric detection. Other butyltins were converted into butyltin hydrides prior to analysis by gas chromatography. It was shown that TBT-contaminated sediments from Marsamxett Harbour, Malta, placed in 0.5 l chambers through which air was displaced by continuous pumping for 11 days released mainly methylbutyltins, with concentrations (as tin) reaching maximum 48,h mean values of 8.7 (Me3BuSn), 22.1 (Me2Bu2Sn) and 93.0,ng m,3(MeBu3Sn) being measured. Other volatile forms of TBT, dibutyltin and monobutyltin were detected in the headspace air, but very infrequently and at much lower tin concentrations (<2,ng m,3). It was also shown that methylbutyltins dissolved in sea-water ([Sn],=,0.2 to 400,ng l,1) were very difficult to exsolve from this medium, even on prolonged evaporation of the solutions using mechanical agitation and active ventilation. The results suggest that emission of methylbutyltins from contaminated sediments probably occurs only from the surface of the material. The environmental implications of these findings in the management of TBT-polluted harbour sediments are discussed. Copyright © 2002 John Wiley & Sons, Ltd. [source] Preliminary evidence for in vitro methylation of tributyltin in a marine sedimentAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 11 2001Alfred J. Vella Abstract Recent reports from our laboratory on the occurrence of methylbutyltins in marine sediments and seawater suggest that these compounds are formed in the environment by the methylation of both tributyltin (TBT) and thatof its degradation products, i.e. dibutyltin and monobutyltin, to give MenBu(4,n)Sn for which n,=,1, 2 and 3 respectively. We investigated the possibility of inducing methylation of TBT in seawater,sediment mixtures in experiments carried out in vitro using environmental materials collected from a yacht marina in Msida, Malta. Three water,sediment mixtures, which were shown to contain TBT, dibutyltin and monobutyltin but no other organotins, were spiked with tributyltin chloride (90,mg in 100,ml sea-water/100,ml sediment); to one mixture was added sodium acetate and to another methanol, to act as possible additional carbon sources, and all mixtures were allowed to stand at 25,°C in stoppered clear-glass bottles in diffused light for a maximum of 315 days. Speciation and quantification of organotins was performed using aqueous phase boroethylation with simultaneous solvent extraction followed by gas chromatography with flame photometric detection. The atmosphere inside the bottles quickly became reducing with abundant presence of H2S, and after an induction period of about 112 days, and only in the reaction mixture containing methanol, methyltributyltin (MeBu3Sn) was observed in both sediment (maximum concentration 0.87 µgSn g,1) and overlying water (maximum concentration 6.0 µgSn l,1). The minimum conversion yield of TBT into MeBu3Sn was estimated to be 0.3%. MeBu3Sn has a significantly lower affinity for sediment than TBT and, therefore, is more mobile in the marine environment, possibly also migrating into the atmosphere to generate a hitherto unsuspected flux of organotin into that phase. Copyright © 2001 John Wiley & Sons, Ltd. [source] | ||||||||||