Identification and differentiation of barbiturates, other sedative-hypnotics and their metabolites in urine integrated in a general screening procedure using computerized gas chromatography-mass spectrometry

Abstract

A gas chromatographic-mass spectrometric procedure is described for the identification and differentiation of sedative-hypnotics and their metabolites in urine. The following 24 barbiturates and thirteen other hypnotics could be detected: acecarbromal, allobarbital, amobarbital, aprobarbital, barbital, brallobarbital, bromisoval, (sec)butabarbital, butalbital, butobarbital, carbromal, clomethiazole, crotylbarbital, cyclobarbital, cyclopentobarbital, diethylallylacetamide, dipropylbarbital, glutethimide, guaifenesin, ethinamate, heptabarbital, hexobarbital, meprobamate, methaqualone, metharbital, methohexital, methylphenobarbital, methyprylone, pentobarbital, phenobarbital, propallylonal, pyrithyldione, secobarbital, thiobutabarbital, thiopental, vinbarbital and vinylbital. The procedure presented is integrated in a general screening procedure (general unknown analysis) for several groups of drugs detecting over 300 drugs and over 1000 of their metabolites. It includes cleavage of conjugates by acid hydrolysis, isolation by liquid-liquid extraction, derivatization by acetylation, separation by capillary gas chromatography, and identification by computerized mass spectrometry. Using mass chromatography with the selected ions m/z 83, 117, 141, 167, 169, 207, 221 and 235, the presence of barbiturates, other hypnotics and/or their metabolites was indicated. The identity of positive signals in the reconstructed mass chromatograms was confirmed by a visual or computerized comparison of the stored full mass spectra with the reference spectra. The sample preparation, mass chromatograms, reference mass spectra and gas chromatographic retention indices are documented.