Direct assay of nonopioid analgesics and their metabolites in human urine by capillary electrophoresis and capillary electrophoresis-mass spectrometry

Capillary electrophoresis (CE) was used for the analysis of nonopioid analgesics and their metabolites directly in urine samples. A simple, reliable screening method was developed that allows identification of the drug and/or its metabolites in urine after oral application of paracetamol, acetylsalicylic acid, antipyrine, ibuprofen, naproxen, ketoprofen and propyphenazone by their migration in CE and by their UV spectra recorded with a diode-array detector in a common CE-UV system with 50 mM borax pH 9.4 as separation buffer. For the CE-electrospray (ESI)-MS coupling a volatile 50 mM ammonium acetate buffer at pH 9.8 was used. In order to analyze the metabolic pattern in more detail different methods were developed for each drug. The separation of the metabolites of acetylsalicylic acid could be improved by injection of the urine sample at the cathodic side of the capillary. In order to identify antipyrine as neutral compound as well as its neutral metabolites a micellar electrokinetic chromatography (MEKC) method was developed. (C) 1999 Elsevier Science B.V. All rights reserved.