Methodology for the development of a drug library based upon collision-induced fragmentation for the identification of toxicologically relevant drugsin plasma samples

The possibility of creating a robust mass spectral library with use of high -performance liquid chromatography-atmospheric pressure-electrospray ioniza tion (HPLC-AP-ESI) for the identification of drugs misused in cases of clin ical toxicology has been examined. Factors reported as influencing the frag mentation induced by "source transport region collision induced dissociatio n" (CID) have been tested in this study (i.e. solvent, pH, different acids or buffer salts and their concentration, different organic modifiers and th e modifier concentration). The tests performed on a few "model drugs" were analysed with use of two different single quadrupole instruments. The large number of mass spectra obtained appears to be affected by the mobile phase conditions to only a minor extent. This also holds for the mass spectra ob tained at two different instruments (laboratories). Subsequently breakdown curves have been measured for about 20 randomly chosen drugs by variation o f the kinetic energy of their ions in the CID zone through changing the fra gmenter voltage. These breakdown curves were used to optimize the fragmente r voltage for each drug. The optimized fragmenter voltages were then applie d by use of a variably ramped fragmenter voltage to acquire mass spectra fo r the library. The chromatographic separations were run on a Zorbax Stable bond column using a 10-mM ammonium formate-acetonitrile gradient method. Sp iked blank serum and patient samples with a total of 40 different drugs wer e extracted with use of a standard basic liquid-liquid extraction (LLE) met hod. A search of significant peaks in the chromatogram by application of th e developed mass spectral library is shown to result in a more than 95% pos itive identification. (C) 2001 Elsevier Science B.V. All rights reserved.