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.