Determination of beta-sympathomimetics in liver and urine by immunoaffinity chromatography and gas chromatography—mass-selective detection

A specific and sensitive method for the determination of several β-agonistic drugs in liver and urine is described. Following clean-up by immunoaffinity chromatography and two different derivatizations, gas chromatography—mass spectrometry with electron-impact ionization is performed. The immunoaffinity chromatography columns were packed with Sepharose-immobilized polyclonal antibodies raised against the β-agonist clenbuterol. Owing to the high clean-up efficiency of the immunoaffinity column large sample volumes can be used (up to 100 ml urine or 25 gram liver). The immunoaffinity sample pretreatment is highly specific and no further sample pretreatment was necessary. Due to the combination of two different derivatizations only GC—MS with electron-impact ionization is necessary to fulfil legal requirements. The first confirmation step consists of a derivatization reaction between the hydroxyl group of the parent compound and trimethylsilane. The second confirmation method is a derivatization to a cyclic derivative with the hydroxyl group and the aliphatic nitrogen group. Limits of determination in liver as well in urine are at the 10 ng/kg or ng/l (ppt) level with acceptable signal-to-noise ratio. The method is suitable for identification and quantification of trace amounts of several similar β-agonistic drugs either used separately or in combination and can be used also for quantification of clenbuterol in liver with regard to levels exceeding the maximum residue limit (MRL) of 1 μg/kg (ppb).