Diagnostic evidence for the presence of β-agonists using two consecutive derivatization procedures and gas chromatography-mass spectrometric analysis

A GC-MS procedure for the detection of different β-agonists in urine samples based on two consecutive derivatization steps is described. The derivatization procedure is based on the consecutive formation of cyclic methylboronate derivatives followed by a second derivatization step with MSTFA on the same extract, forming TMS derivatives. Injections in the GC-MS system may be carried out after each one of the derivatization steps, obtaining enough information for unambiguous identification. Limits of detection for the two derivatization steps ranged from 0.5 to 5 ng/ml. This procedure was tested with the β-agonists bambuterol, clenbuterol, fenoterol, formoterol, salbutamol, salmeterol, α-hydroxy-salmeterol and terbutaline.