A sensitive and robust confirmatory method for determination of steroid esters in blood serum is essential for reliable monitoring of possible illegal use of steroid hormones as growth promoters in meat production. A previously used sample preparation methodology was improved. The procedure consists of protein precipitation and removal of phospholipids by dispersive SPE Supel™ QuE Z-Sep (Sigma-Aldrich) followed by clean-up on alumina column and LC-MS/MS measurement. The modified method has been validated according to Commission Decision 2002/657/EC. Validation parameters for determination of six testosterone esters and five nortestosterone esters in bovine and porcine blood serum are presented in this article. Decision limits for all analytes were observed in the range 10-20 pg mL. The method described is considerably robust for bovine and porcine serum analyses and can be applied both for screening and confirmatory determination in routine residue monitoring.

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 Supel-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. 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.

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To investigate potential residues in tissues arising from naturally occurring low levels of chloramphenicol in plant material, feeding studies were conducted with chickens. A common chicken feed was prepared containing 0, 10, 50 and 200 μg kg chloramphenicol and levels were confirmed by LC-MS/MS. Four separate groups of broiler chickens, eight animals in each group, were fed all their 35-day life with this contaminated feed. They were allowed ad libitum access to this feed and fresh water. After slaughtering the chickens, the residues in muscle and liver tissues were determined using GC/MS-NCI method. No residues were detected in tissues of animals from groups fed with feed containing 0, 10 or 50 µg kg. Low chloramphenicol residual concentrations were observed in a few of the muscle samples obtained from the group of chickens fed with feed containing chloramphenicol in added concentration 200 µg kg. No residues were detected in the remaining samples of this group. These results indicate that when residues of chloramphenicol are detected it is in all probability through illegal use.