Multiresidue analysis of beta(2)-agonists in human and calf urine using multimodal solid-phase extraction and high-performance liquid chromatography with electrochemical detection

Various beta(2)-agonists are used as illegal growth promoters in man and in animals. We developed a multiresidue procedure for the analysis of four be ta-agonists in human and calf urine. The sample was pre-extracted with an E xtrelut column at alkaline pH. The beta-agonists were eluted with a mixture of tert.-butylmethyl ether and hexane. Then the extract was further cleane d with a mixed mode SPE column, or with a combination of immunoaffinity chr omatography (IAC) and the mixed mode SPE column. The IAC column contained a ntibodies against salbutamol, which were suitable for multiresidue extracti ons. The extract was then brought onto a mixed mode SPE column at an acidic pH. The column was washed with 70% methanol in water. Thereafter, the beta -agonists were eluted with ammoniated ethanol-hexane. The extract was analy sed with an HPLC method with electrochemical detection. The beta-agonists w ere separated on a reversed-phase column using a mobile phase buffered at p H 5.5 and containing an ion-pair reagent. Recoveries were higher when the I AC procedure was not performed (90-105% vs. 65-75%), but the extracts were cleaner when the latter step was included. Detection limits in human and ca lf urine were in the low ng/ml range. The study indicated that beta(2)-agon ists can be analysed in human and calf urine without the selectivity of a m ass spectrometer, but that comprehensive clean-up is required to avoid the interference of urine matrix components. (C) 1999 Elsevier Science B.V. All rights reserved.