SPE-HPLC method for determination of ketoconazole and clotrimazole residues in cow's milk

A simple confirmatory method for HPLC-UV determination of ketoconazole and clotrimazole residues in cow's milk after solid phase extraction (SPE) is reported in this article. The samples were deprived of proteins and lipids by treating with acetonitrile and consequent extraction in n-hexane. Extracts were further cleaned-up and concentrated via solid phase extraction. The analytes were determined quantitatively using a validated high performance liquid chromatography method. The method was linear in the range of 0.1-1.0 µg mL-1 for both analytes. Limits of detection and quantification for both analytes were equal to 0.01 and 0.1 µg mL-1, respectively. Important parameters influencing the extraction efficiency were investigated and then optimized; the proposed method was applied to the analysis of milk samples. Satisfactory recoveries were obtained in the range of 95.9-101.78% using SPE.