Determination of testosterone esters and estradiol esters in bovine and porcine blood serum.

Monitoring of steroid esters in blood serum is desirable in order to detect the possible illegal use of natural hormones as growth promoters. A method for the determination of testosterone propionate, testosterone benzoate, testosterone isocaproate, testosterone decanoate and estradiol benzoate in bovine and porcine blood serum was developed. The procedure consists of protein precipitation and removal of phospholipids using a HybridSPE®-Phospholipid column followed by clean-up on a hydrophilic modified styrene polymer SupelTM-Select HLB column and LC-MS/MS measurement. The method was validated according to Commission Decision 2002/657/EC. Decision limits for all analytes were observed in the range 5-30 pg ml-1. The method was shown to be robust for bovine and porcine serum analyses and can be applied for both screening and confirmatory determination in routine residue monitoring.