J. Fischer et al., DETERMINATION OF IVERMECTIN IN BOVINE PLASMA BY COLUMN-SWITCHING LC USING ONLINE SOLID-PHASE EXTRACTION AND TRACE ENRICHMENT, Journal of pharmaceutical and biomedical analysis, 11(3), 1993, pp. 217-223
Ivermectin is a potent avermectin anthelmintic, derived from the soil
organism Streptomyces avermitilis. Because of its potency, it is admin
istered in very low doses (200 mug kg-1), giving rise to plasma levels
in the ppb region, and hence sensitive methods are required for its d
etermination in biological samples. A method is described for the dete
rmination of ivermectin in bovine plasma, based on a commercially avai
lable C18 column employing a mobile phase composed of acetonitrile-wat
er-isopropanol (40:40:35, v/v/v). Extraction from plasma is carried ou
t on-line using coupled-column technology; switching between the extra
ction and analytical columns is achieved using a six-port column-switc
hing valve. The method is linear over the range 2-100 ng ml-1 (r = 0.9
994) and has a limit of detection of 0.8 ng ml-1 (signal-to-noise rati
o = 3). Reproducibility of the method, expressed as the overall mean r
elative standard deviation, is 6.7% (intra-assay) and 3.8% (inter-assa
y). The mean recovery of the drug from plasma is 76.4%. The method is
simple and economical in its execution and is sufficiently reproducibl
e to obviate the need for an internal standard.