Gas Chromatography-flame Photometric Detection Research Articles

The determination of organotins (TBT) in fish and shellfish via gas chromatography–flame photometric detection and direct current plasma emission spectroscopy (GC–FPD/DCP)

AbstractGas chromatography (GC) has been interfaced very simply and inexpensively with a flame photometric detector (FPD) and a direct current plasma (DCP) atomic emission spectrometer in order to perform highly specific and selective determination of organotins in fish and shellfish samples. GC–FPD studies employed a fused‐silica, megabore column with a thin, immobilized stationary phase of DB‐17 (1 μm thickness), with a commercially available GC–FPD instrument. No prior alkylation or hydridization reactions were performed on the organotins; rather they were separated as the original, native species. Separate GC–FPD and GC–DCP injections and quantitative determinations have been performed, though simultaneous FPD/DCP detection on a single injection is suggested. This permitted routine qualitative and quantitative determinations of organotin species in complex food matrices (fish/shellfish) via both element selective detectors. Isothermal GC–FPD/DCP conditions permitted baseline resolution of all four tin species of interest today: monobutyl‐, dibutyl‐, tributyl‐ (TBT), and tetrabutyl‐tin. Optimization of the GC–DCP interface was accomplished, followed by a determination of detection limits and linearity of the calibration plots, and a comparison of the results with those obtained by the newer GC–FPD approach (which was also developed here). In three sample instances, qualitative and quantitative results for naturally occurring and spiked levels agreed for both the GC–FPD and GC–DCP approaches. Improved sample preparation and extraction procedures have been developed for organotins from fish samples involving extraction with an organic solvent, concentration, saponification, back‐extraction, and injection of the eluent onto the GC column. Quantitative levels of organotins (solely TBT) in fish and shellfish are reported for samples from Europe, Korea, Scandinavia, and the USA.

Determination of reduced sulfur compounds in aqueous solutions using gas chromatography-flame photometric detection

A method for simultaneous analysis of hydrogen sulfide (H/sub 2/S), methyl mercaptan (CH/sub 3/SH), carbon disulfide (CS/sub 2/), dimethyl sulfide (DMS, CH/sub 3/SCH/sub 3/), and dimethyl disulfide (DMDS, CH/sub 3/SSCH/sub 3/) in aqueous solutions is described. The reduced sulfur compounds are released from the aqueous sample (50-200 mL) by purging with N/sub 2/ and then trapped cryogenically in a U-shaped sample tube with liquid nitrogen. The sample tube was sealed with end caps and placed in a portable freezer. Under stable conditions in the laboratory, the sulfur compounds are released by controlled heating and injected onto packed column gas chromatograph with a flame photometric detector. The precision of the method for environmental samples was better than +/- 5% for all compounds except for H/sub 2/S, for which the precision was +/- 25%. The detection limits for H/sub 2/S, CH/sub 3/SH, CS/sub 2/, DMS, and DMDS were 1, 0.6, 0.2, 0.2, and 0.4 ng x L/sup -1/ S, respectively, in a 200-mL natural sample. Analyses of environmental samples have been successfully performed with the described method.

Determination of barbiturates in plasma by gas chromatography-flame photometric detector after N,N′-dimethylthiomethyl derivatization

A specific and sensitive gas chromatographic (GC) procedure with the flame photometric detector (FPD) was developed for determination of barbiturates such as barbital, allobarbital, secobarbital, phenobarbital and thiopental in plasma. In order to evaluate the performance of the FPD, the results were campared with those of the flame ionization detector (FID).

Comprehensive method for determination of aquatic butyltin and butylmethyltin species at ultratrace levels using simultaneous hydridization extraction with gas chromatography-flame photometric detection

An ultratrace method for the analysis of aquatic anthropogenic butyltin and mixed methylbutyltin species using simultaneous hydridization with sodium borohydride and extraction into dichloromethane is described. The detection limits for a 100-mL sample are 7 ng of Sn/L for tetrabutyltin, 7 ng of Sn/L for tributyltin, 3 ng of Sn/L for dibutyltin, and 22 ng of Sn/L for monobutyltin. Detection limits of approximately 1-2 ng of Sn/L for tri- and tetrabutyltin and less than 1 ng of Sn/L for dibutyltin species were achieved with 800-mL samples. The presence of tetrabutyltin in harbor waters is reported. 39 references, 9 figures, 2 tables.

Structure-response relationship of gas chromatography-flame photometric detection to some organophosphorus compounds

A variety of organophosphorus compounds was studied with respect to their response to the gas chromatographic-flame photometric detector. Contrary to the experience of some investigators, the molar response of phosphorus was found to be linear only within homologous series. Compounds containing the dialkylaminoalkyl moiety on phosphorus are in the low sensitivity (50% of the “normal” molar sensitivity) range. Some compounds such as phosphodihalides (fluoro or chloro) are 30% or more above the “norm”. Comparative data are given for selected compounds on the flame ionization and thermionic nitrogen-phosphorus detectors. A postulated mechanism is given for explaining some of the differences.

A rapid GC method of monitoring Mesurol (4-(methylthio)-3,5-xylyl-N-methyl carbamate) and its sulfoxide and sulfone metabolites and their persistence in lowbush blueberries.

A facile analytical procedure was developed for determining Mesurol (4-(methylthio)-3,5-xylyl-N-methyl carbamate) and its oxidation products in blueberries. It involved blending with acetone, partition with chloroform and derivatization with trifluoroacetic anhydride and quantitation by gas chromatography/flame photometric detector (GC/FPD). The method showed good recoveries for Mesurol and its sulfoxide at the 0.1 ppm level and Mesurol sulfone at the 0.3 ppm level with a 25 g sample. It was applied to monitor levels of the insecticide and its oxidation products on field-treated blueberries. The sensitivity of the method may be increased 5-fold by the inclusion of a clean-up step. The optimal conditions for the detection of Mesurol TFA by the modified Bendix sulphur/phosphorus emission detector operating in the sulphur mode required an oxygen/hydrogen ratio of 0.38, for a column flow of 60 ml/min. The minimum detectable amounts of the TFA derivatives of Mesurol, its sulfoxide and sulfone were calculated as 1.3, 2.3 and 5.8 X 10(-11) g/sec, respectively.

The Determination of Trace Mercaptans and Sulfides in Natural Gas by a Gas Chromatography-Flame Photometric Detector Technique

The Determination of Trace Mercaptans and Sulfides in Natural Gas by a Gas Chromatography-Flame Photometric Detector Technique