GC-MS determination of anabolic steroids after multi-immunoaffinity purification

For many years, EC regulations have prohibited the use of anabolic agents in food-producing animals. Multiple screening methods have been published, but some lack specificity and some are difficult to apply when screening for unknowns in surveillance programmes. This paper presents a new and powerful technique, combining multiresidue immunoaffinity chromatography and GC-MS, for the simultaneous identification and semi-quantification of various anabolic steroids in urine and faeces samples of bovine origin. It should reduce the cost, time and effort of screening by limiting the number of tedious clean-up steps and analyses required. A preliminary extraction step is applied to the individual biological specimens: solid-phase extraction followed by enzymatic digestion in the case of urine samples and a single liquid extraction step for faeces. This step is followed by a first clean-up step involving both a solid-phase column and a rapid RP-HPLC separation. The individual biological fractions (urine or faeces) are further purified on a multiresidue immunoaffinity chromatographic gel (MIAC-steroids-CER) so as to decrease interferences due mainly to background signals. A final trimethylsilyl derivatization is followed by the analysis of the biological samples by a sensitive and specific GC-MS procedure.