title: Direct determination of avermectins in plasma at nanogram levels by high-performance liquid chromatography.
abstract: 22,23-Dihydroavermectin B1a (I) is determined in animal plasma over the concentration range 5-60 ng/ml by reverse-phase high-performance liquid chromatography (HPLC) with UV photometric detection. Prior to HPLC the sample is isolated by gravity-fed adsorption column chromatography on Florisil. The delta 2 isomer of I (designated as compound III) is used as an internal standard, and the conversion of I to this isomer by base hydrolysis is described. An accuracy of 2 ng/ml (mean deviation) and a precision in the range of 1-3 ng/ml (standard deviation) were observed for the method. The limit of detection is 2 ng/ml based on the background observed for normal cattle plasma. The method is applicable to bioavailability studies of I at usual therapeutic concentrations.
mesh_terms: D000818:Animals; D002417:Cattle; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D007536:Isomerism; D007559:Ivermectin / Q000031:analogs & derivatives*; D007783:Lactones / Q000097:blood*; D008832:Microchemistry; D013050:Spectrometry, Fluorescence; D013997:Time Factors
chemical_list: D007783:Lactones; D007559:Ivermectin; C019264:avermectin