Broad spectrum drug identification directly from urine, using liquid chromatography-tandem mass spectrometry

Background: Currently the rate-limiting step for mass spectrometric analysi s of drugs-in biological samples is sample preparation. Many gas chromatogr aphy/mass spectrometry (GC/MS) methods are specific for a certain class of compounds, requiring extraction and/or derivatization before analysis. The purpose of this study was to develop a broad spectrum liquid chromatography /mass spectrometry (LC/MS) procedure that allowed for direct analysis of ur ine specimens with potential for quantitative analysis. Methods: We modified a commercially available column-switching instrument, the REMEDi HS from BioRad Diagnostics, to make it compatible with atmospher ic pressure ionization. The system we developed was based on electrospray i onization and used three LC columns to extract, purify, and separate drugs directly from urine specimens, Drugs and metabolites were tentatively ident ified on the basis of retention times and (M+H)(+) ions. Tandem mass spectr ometry (MS/MS) was used to confirm the qualitative identification of suspec ted drugs, using data-dependent acquisition. For quantitative analysis, the cocaine metabolite benzoylecgonine was analyzed using isotope dilution and selected reaction monitoring. Results: Seventeen basic drugs from a variety of classes of compounds were identified directly from urine without the need for prior sample extraction , using LC and MS/MS. Quantitative analysis was demonstrated for benzoylecg onine. When benzoylecgonine-d(3) was used as the internal standard, the met hod was linear from 30 to 10 000 mu g/L (range tested). At these concentrat ions, the within-run accuracy was +/- 10% of the target concentration, with CVs <10%. Analytical results by LC/MS/MS compared favorably with GC/MS val ues for 50 benzoylecgonine-containing specimens and for 25 negative specime ns. Conclusions: The ability to directly analyze urine for a wide variety of dr ug classes, combined with the sensitivity and specificity of LC/MS/MS makes this technique attractive for many clinical, forensic, and biotechnology a pplications. (C) 1999 American Association for Clinical Chemistry.