METHOD FOR THE ISOLATION AND LIQUID-CHROMATOGRAPHIC DETERMINATION OF CHLORAMPHENICOL IN MILK

A method for the isolation and liquid chromatographic determination of chloramphenicol in milk is presented. Chloramphenicol-fortified or blank milk samples (0.5 mL) were blended with octadecyl-silyl (C18) derivatized silica (2 g). The C18/milk matrix was used to prepare a column that was washed with hexane (8 mL) followed by benzene (8 mL). Chloramphenicol was then eluted with ethyl acetate (8 mL). The eluate contained chloramphenicol, which was free from interferences when analyzed by high-performance liquid chromatography (HPLC) utilizing UV detection (278 nm, photodiode array; minimum detectable limit 1.25 ng on-column). Linearity (0.999 ± 0.001), average percentage recovery (68.8 ± 8.3%), and inter-(11.6 ± 6.9%) and intraassay (1.4%) variabilities, for the concentrations examined (62.5, 125, 250, 500, 1000, 2000 ng/mL milk), were indicative of an acceptable method for chloramphenicol. The method uses small volumes of solvents, has a limited number of sample manipulations, and requires no pH adjustments or back-washing of extracts, making this method attractive when compared to classical isolation procedures for chloramphenicol. © 1990, American Chemical Society. All rights reserved.