Gas chromatographic-mass spectrometric determination of plasma selegiline using a deuterated internal standard.

A gas chromatographic-mass spectrometric method is described for the determination of plasma selegiline. Tetradeuteroselegiline was synthesized and served as the internal standard. Human plasma samples (1 ml) containing 1-6 ng of selegiline were acidified, washed with diethyl ether-hexane, then alkalinized and extracted with heptane-isoamyl alcohol. Analytical separations were performed on a dimethylsilicone capillary column. Detection was by selected ion monitoring of the electron impact generated m/z 96 and 100 alpha-cleavage fragments of drug and internal standard, respectively.     

Gas chromatographic-mass spectrometric determination of oxolinic acid in fish using selected ion monitoring

A gas chromatographic-mass spectrometric (GC-MS) method is described for the determination of oxolinic acid in fish tissues. oxolinic acid is reduced with sodium tetrahydroborate to permit GC analysis. The sample is homogenized with phosphate buffer (pH 6) and extracted with ethyl acetate. The extract is partitioned between sodium hydrogencarbonate solution and the aqueous phase is acidified and re-extracted with ethyl acetate. The residue from the ethyl acetate extract is dissolved in methanol and reduced with sodium tetrahydroborate. The reduction product is extracted with diethyl ether and analysed by GC-MS in the selected ion monitoring mode for the ions at m/z 204, 219 and 176. The detection limit is 0.001 mg/kg and the recoveries were 95.6% [relative standard deviation (R.S.D.) 7.7%] at 0.1 mg/kg and 72.9% (R.S.D. 13.3%) at 0.01 mg/kg fortification levels in fish.     

Gas chromatographic-mass spectrometric method for the determination of selenium in biological samples.

The determination of selenium by capillary gas chromatography-mass spectrometry (GC-MS), using an enriched stable isotope 76Se as internal standard, is described. Reference values for selenium in human biological fluids (serum, red blood cells and urine) are reported. With the advent of new compact capillary GC-MS (benchtop) instruments, this method will be very simple and accurate for routine analysis.     

Gas chromatographic-mass spectrometric determination of polycyclic aromatic hydrocarbons formed during the pyrolysis of phenylalanine

The formation of polycyclic aromatic hydrocarbons (PAHs) during pyrolysis process of phenylalanine had been studied. Ten PAHs, including fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzo[k]fluoranthene, benzo[e]pyrene, and benzo[a]pyrene were analyzed by gas chromatography-mass spectrometry using selective ion monitoring mode. This technique offers the capability to analyze trace amounts of PAHs in phenylalanine pyrolyzates. The pyrolysis was carried out in a micro-furnace with quartz furnace liner. The injection was conducted with glass pelletizer syringe to avoid metal contamination. Qualitative results were obtained at 900 degrees C and quantitative analysis of 10 PAHs was done for 700 and 900 degrees C.     

Gas chromatographic-mass spectrometric determination of sulfolane in wetland vegetation exposed to sour gas-contaminated groundwater

Described is a GC-MS method for the determination of the levels of sulfolane (tetrahydrothiophene 1,1-dioxide, C4H8O2S; a water miscible chemical used in the sweetening of sour gas) in wetland vegetation (roots, shoots, berries, seeds, grasses, and leaves). The technique was developed to provide positive detection of sulfolane in a variety of wetland vegetation and to determine the extent to which sulfolane may translocate within the plants. Vegetation samples collected at a sour gas processing facility were extracted using a two-stage process which utilized a back extraction of a water extract with toluene. The main advantages of this procedure were: good extraction efficiency (recovery of 80+/-12%), exclusion of most of the highly polar co-extractives during the toluene back extraction step, and a final extract well suited to routine GC-MS selected ion monitoring of sulfolane with a detection limit of 90 ng g(-1) (wet mass). In general, the method was rugged, based on a study period of 18 months in which over 175 runs were conducted.     

Gas chromatographic-mass spectrometric determination of intact C3-hydroxylated benzodiazepine glucoronides in urine.

A method is described for the determination C3-hydroxylated benzodiazepine glucuronides in biological samples. Oxazepam and lorazepam glucuronides are measured as methyl esters and trimethylsilyl derivates by a gas chromatographic procedure. The applicability of the method has been tested on the urine of rats, guinea pigs, rabbits and man, receiving oxazepam orally. Oxazepam glucuronide was not found in rat urine but it was present in the urine of rabbits (5.7% of the administered dose), guinea pigs (9.5%) and man (13.4-26.9%).     

Gas chromatographic-mass spectrometric analysis of volatile constituents in saliva

Present methods for the development of metabolic profiles are limited to the use of headspace techniques and solvent extraction methods. A new method for the development of saliva profiles which provides information complementary to existing analyses has been developed. The results of the developed methodology provide a reliable, reproducible method for metabolic profiling. Gas chromatographic-mass spectrometric analysis of the volatile constituents provided positive identification of 39 compounds. Application of the developed protocol toward the investigation of saliva as a vehicle for the non-invasive detection of certain pathological states, specifically diabetes mellitus and liver disorders, may be possible.     

Gas chromatographic-mass spectrometric determination of macrolide antibiotics in beef and pork using single ion monitoring

A gas chromatographic-mass spectrometric (GC-MS) method using single ion monitoring (SIM) is described for the determination of residual macrolide antibiotics, oleandomycin, kitasamycin, spiramycin and tylosin, in beef and pork. For GC-MS determination, oleandomycin is acid hydrolysed to desoleandomycin and acetylated, in the same way as erythromycin. However, for elution from a GC column, the carbon-carbon double bonds in the antibiotics must be hydrogenated to single bonds before acid hydrolysis. Kitasamycin and spiramycin are therefore converted into hydroforocidine acetate and tylosin into hydro-O-mycaminosyl tylonolide acetate, which are determined by GC-MS with SIM.     

Thermospray liquid chromatographic-mass spectrometric analysis of mutagenic substances present in tryptophan pyrolysates

During protein pyrolysis, as can occur when broiling meat or fish, mutagenic substances are formed, as shown by in vitro mutagenicity assays. Some of the most active compounds have been shown to originate from tryptophan (Trp). Hundreds of grams of Trp had to be used previously to study the formation of these compounds by classical separation and detection methods. Studies have been made of the formation of two active heterocyclic amines, 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2), by heating Trp at different temperatures and for different periods at time. Advantage was taken of the high selectivity and sensitivity of thermospray liquid chromatography-mass spectrometry coupling, which permitted the use of much smaller amounts (10 g) of starting material. These conditions permit a more accurate control of the pyrolysis temperature and the method of extraction can be shortened and simplified. The results show that Trp-P-1 and Trp-P-2 were already formed at 250 degrees C. These substances were detectable in the low ppb range, i.e., less than the threshold levels necessary to elicit a positive response in the Ames test under standard conditions.     

Capillary gas chromatographic-mass spectrometric determination of buspirone in plasma

Methods for determining buspirone plus a deuterated analogue and for buspirone alone in plasma samples are described. Analytes are prepared from plasma by liquid extraction into n-butyl chloride and subsequent back-extraction clean-up steps. Instrumental analysis involves selected-ion monitoring gas chromatography-mass spectrometry with fused-silica capillary chromatography. Quantification is in the range 0.05-10 ng/ml with acceptable accuracy and precision.     

Gas chromatographic-mass spectrometric method for the qualitative and quantitative determination of disaccharides and trisaccharides in honey

An improved method has been developed to identify and quantify honey disaccharides and trisaccharides by gas chromatography and mass spectrometry. The procedure, based on mass spectral and retention data ("retention time windows") determined on two capillary columns with different stationary phases allowed the identification and quantitation in honey of 16 disaccharides and 9 trisaccharides, some of which were not previously identified by GC. The reliability of the analytical results was considerably improved by the use of this procedure: several unidentified disaccharides and trisaccharides were detected, and their presence was taken into account in the quantification.     

Liquid chromatographic-mass spectrometric determination of post-harvest fungicides in citrus fruits

Liquid chromatography (LC)-atmospheric pressure ionisation (API)-mass spectrometry (MS) has been used to determine residues of five fungicides in oranges with a minimum sample cleanup. Atmospheric pressure chemical ionisation (APCI) and electrospray (ES) were compared and both gave similar results in terms of sensitivity and structural information. The main ions were [M+H]+ for carbendazim, imazalil, thiophanate methyl and thiabendazole, and [M+H-C4H9NHCO]+ for benomyl. Samples were extracted with sodium sulphate and ethyl acetate. Although benomyl and thiophanate methyl were transformed through the extraction procedure to carbendazim, the method showed good precision (<13%) and recovery (>70%), except for thiophanate methyl (50%), whilst also yielding limits of detection (<0.03 mg kg(-1)) that are adequate for the determination of the studied fungicides in oranges.     

Gas chromatographic-mass spectrometric investigation of phenoxypropanoic acid derivatives possessing herbicidal activity

Fluazifop-butyl, haloxyfop-ethoxyethyl and quizalofop-ethyl, active ingredients of new selective herbicidal preparations, as well as their metabolites converted in to corresponding methyl esters were separated on several gas chromatographic columns. Bromination of fluazifop esters increased significantly the response of the electron-capture detector. Electron impact mass spectra of all the compounds investigated were recorded, and characteristic ions suitable for selected ion monitoring are given.