Derivatization-free determination of short-chain volatile amines in human plasma and urine by headspace gas chromatography-mass spectrometry.

BACKGROUND: Short-chain volatile amines (SCVA) are an interesting compound class playing crucial roles in physiological and toxicological human settings. Dimethylamine (DMA), trimethylamine (TMA), diethylamine (DEA), and triethylamine (TEA) were investigated in detail. METHODS: Headspace gas chromatography coupled to mass spectrometry (HS-GC-MS) was used for the simultaneous qualitative and quantitative determination of four SCVA in different human body fluids. Four hundred microliters of Li-heparin plasma and urine were analyzed after liberation of volatile amines under heated conditions in an aqueous alkaline and saline environment. Target analytes were separated on a volatile amine column and detected on a Thermo DSQ II mass spectrometer scheduled in single ion monitoring mode. RESULTS: Chromatographic separation of selected SCVA was done within 7.5 minutes. The method was developed and validated with respect to accuracy, precision, recovery and stability. Accuracy and precision criteria were below 12% for all target analytes at low and high levels. The selected extraction procedure provided recoveries of more than 92% from both matrices for TMA, DEA and TEA. The recovery of DMA from Li-heparin plasma was lower but still in the acceptable range (>75%). The newly validated method was successfully applied to plasma and urine samples from healthy volunteers. Detected concentrations of endogenous metabolites DMA and TMA are comparable to already known reference ranges. CONCLUSION: Herein, we describe the successful development and validation of a reliable and broadly applicable HS-GC-MS procedure for the simultaneous and quantitative determination of SCVA in human plasma and urine without relying on derivatization chemistry.

Prevention of tricyclic antidepressant adsorption loss with diethylamine during solvent evaporation.

The authors evaluated the adsorption loss of tricyclic antidepressants in analytical procedures with solvent extraction and evaporation. In standard procedures with the use of triple solvent extraction between alkalinized and acidified samples before chromatographic analysis, the adsorption loss was more significant with the demethylated metabolites. As much as 50% adsorption loss can occur; this irreversible loss can be accounted for entirely during the solvent evaporation step. Because of differential adsorption loss among parent drugs, metabolites, and internal standards, the analytical methods usually had wide within-day and day-to-day variations. The authors found that the addition of as little as 0.05% diethylamine to the extract before evaporation completely eliminated the adsorption loss of amitriptyline-nortriptyline, imipramine-desipramine, and doxepin-desmethyldoxepin. with subsequent improvement in procedure performance. This simple modification can be adopted readily by all laboratories that use solvent extraction and subsequent chromatographic analysis of tricyclic antidepressants.

Determination of disulfiram and metabolites from biological fluids by high-performance liquid chromatography.

A high-performance liquid chromatographic method is described for the determination of disulfiram, diethyldithiocarbamate, diethyldithiocarbamate methyl ester, carbon disulfide, and diethylamine from a single sample of plasma or urine. The analytical procedure is based on a quantitative stepwise extraction of disulfiram and diethyldithiocarbamate methyl ester, or the conversion of diethyldithiocarbamic acid, carbon disulfide and diethylamine to diethyldithiocarbamate methyl ester for chromatographical determination. The procedure is specific, precise and simple. The application of the analytical methods developed for the determination of disulfiram and the various metabolites in plasma from mice given disulfiram intraperitoneally or humans given Antabuse orally is illustrated.