Application of hyphenated mass spectrometric techniques to the determination of corticosteroid residues in biological matrices

Fifty years after the discovery of natural corticosteroid hormones and their anti-inflammatory properties many synthetic derivatives of these molecules are now available. Most are widely used in human and veterinary medicine, legally but under regulated conditions. These compounds can also be used as growth promoters in animal breeding, although such use is illegal in Europe. Consequently, analytical methods have been developed to monitor use of corticosteroids in cattle. This paper, based on the authors experience and the main relevant literature, describes the different mass spectrometric approaches used for measurement of corticosteroid residues (parent drug, metabolites, and esters) in biological matrices (urine, meat, hair), including gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS2). The respective advantages of liquid chromatography and gas chromatography, in conjunction with different derivatisation reactions, are discussed. The behavior of corticosteroids with different ionization techniques is also discussed. Application to monitoring corticosteroid misuse and to investigation of pharmacokinetics and metabolism in bovine species is described and new data are presented relating to elimination and hair fixation kinetics for free and ester forms and the nature and proportions of corticosteroid phase I and phase II metabolites. Finally, this work reviews ten years experience of the use of a variety of mass spectrometric techniques for analysis of corticosteroids in animals produced as food.