Preparation of an immunoaffinity column and its application in sample cleanup for methandrostenolone residues detection.

Methandrostenolone (MA) is a steroid used as veterinary medicine on stockbreeding to promote animal growth. The use of MA has been strictly regulated because of its harmful effect on consumers. This paper describes the production of polyclonal antibody (pAb) against MA, the preparation of immunoaffinity column (IAC) and its potential application to the selective extraction of MA residues from animal tissue and feed samples. The produced pAb exhibited good sensitivity to MA with an IC(50) value of 5.6 ng/mL. The cross-reactivity values of the antibody with MA structurally related compounds of testosterone propionate (TP) and trenbolone (TR) were lower than 0.6%. By coupling the produced antibody with CNBr-activated Sepharose 4B, an IAC was prepared. 2% methanol and 80% methanol were selected as loading and eluting solution by optimization. The maximum capacity of the column for MA was approximately 334 ng/mL gel. The average recovery of 20, 40 and 60 ng/mL MA standard solutions from IACs was 97.9% with the relative standard deviation (RSD) among columns of 6.7%. After 3 times of repeated usage, the column capacity and recovery rate still remained 82.0% and 92.6% respectively. The IACs were then challenged with MA-fortified animal tissue and feed samples, recoveries of MA were found to be in the range of 83.5-99.7%.