Use of molecularly imprinted solid-phase extraction for the selective clean-up of clenbuterol from calf urine

A feasibility study was performed in order to study the possibilities in us ing molecularly imprinted polymers (MIPs) as sorbent material in solid-phas e extraction (MISPE) for clean-up of clenbuterol from urine. A binding stud y of clenbuterol in several solvents was performed on a clenbuterol imprint ed polymer as well as on a blank polymer. These binding experiments were us ed to find suitable loading, washing and elution solvents for the MISPE pro cedure. Extraction of clenbuterol from calf urine was performed by directly loading a 10-ml urine sample onto the MIP column. Thereafter the column wa s washed with 10 mi of acetonitrile containing 1% acetic acid, and finally clenbuterol was eluted with 6 mi of methanol containing 10% acetic acid. A recovery of 65% was obtained. This recovery could be increased up to 75% if a sample volume of 1 ml was used or up to 100% if urine was freeze-dried a nd the residue was dissolved in acetonitrile and spiked with clenbuterol pr ior to analysis. Chromatograms of the wash and eluate solutions show an eff icient clean-up, which supports the potential of MISPE for clean-up of trac e amounts of clenbuterol from calf urine. (C) 2000 Elsevier Science BN. All rights reserved.