DETERMINATION OF IVERMECTIN RESIDUES IN THE TISSUES OF ATLANTIC SALMON (SALMO-SALAR) USING HPLC WITH FLUORESCENCE DETECTION

A sensitive, accurate and reproducible assay for the determination of residual concentrations of ivermectin in the tissues of farmed Atlanti c salmon is described. The assay employs the clean-up of an acetonitri le extract of salmon tissue on a Bond-Elut Cg column, followed by deri vatization with trifluoroacetic acid anhydride. Following separation u sing HPLC, 22,23-dihydroavermectin B1a is determined using fluorescenc e detection. The limit of detection of the assay is 1 ng per g tissue. Liver, taken from fish treated experimentally with ivermectin, was fo und to contain higher concentrations of 22,23-dihydroavermectin B1a th an any other tissue examined. The half-life of 22,23-dihydroavermectin B1a was similar in all tissues studied, ranging from 89 to 98 degree days.