Abstract
An HPLC method is described for the simultaneous determination of sulfadiazine (SDZ) and trimethoprim (TMP) residues in cultured gilthead sea bream tissues (muscle plus skin, liver, gills, fat, and kidney). Tissue samples are extracted with dichloromethane and the analytes are partitioned into hydrochloric acid, to be further analysed isocratically on a Nucleosil 100, C18 reverse-phase column, using a mobile phase of acetonitrile : 10 mM phoshoric acid (16:84, v/v).
The UV detection is performed by using a spectrophotometric detector monitored at 271 nm. The limits of detection of SDZ and TMP in the edible part of fish are 3.1 ng/g and 18.2 ng/g at a signal to noise ratio of 3:1. The average recovery for SDZ is 82.1%, in muscle plus skin, and ranges from 77.8% to 87.4 % in the other tissues. The average recovery for TMP is 66.7% in muscle plus skin, and ranges from 71.7% to 83.1 % in the other tissues.
ACKNOWLEDGMENTS
The authors wish to thank VETERIN S.A. for their financial support, ICTHYS S.A. for their kind donation of the fish feed, and MEDOUSA S.A. for hosting the experiment on their farm. Special gratitude is expressed to Dr. D. J. Fletouris for his assistance and critical review of the manuscript.