Validation of a multiresidue liquid chromatography–tandem mass spectrometric method for the quantitation and confirmation of corticosteroid residues in urine, according to the proposed SANCO 1085 criteria for banned substances Original Research Article

A multiresidue method for the analysis for five corticosteroids (dexamethasone, flumethasone, fluorometholone, beclomethasone and triamcinolone acetonide) in urine was developed and validated. The method permits quantification and confirmation of the analytes according to the proposed EU (SANCO 1085/2000) criteria for banned substances. The method involves an initial enzymatic hydrolysis step with subsequent clean-up using solid phase extraction (SPE). Extracts were analysed by liquid chromatography–tandem mass spectrometry (LC–MS) (atmospheric pressure chemical ionization (+) ion mode). Enzymatic hydrolysis conditions were examined using samples incurred with dexamethasone. The method was validated using bovine urine fortified at levels of 1, 2 and 5 ng ml−1. The mean recovery was >60% for all analytes. Within laboratory repeatability for the range of analytes lies between 2 and 17% and within laboratory reproducibility lies between 7 and 29%. Decision limits (2 ng ml−1) and detection capabilities (2–3 ng ml−1) have also been established for each analyte. Linearity (Rsq>0.99) was established for each analyte over the concentration range of 0–18 ng ml−1 (matrix equivalent). The method has also been validated as a confirmatory method for all analytes (except beclomethasone). Four identification points (one precursor ion and two product ions) and a minimum of one ion ratio was monitored for each compound. All measured ion ratios in the sample correspond to those of the standard analyte at comparable concentrations within established tolerances outlined by the proposed SANCO 1085/2000 criteria. The method has also been successfully evaluated using incurred urine.