Application of a standardized coextractive cleanup procedure to routine high-performance liquid chromatography assays of teicoplanin and ganciclovir in plasma

Deproteinization of plasma samples with acetonitrile followed by coextracting acetonitrile and lipophilic solutes with chloroform, as already proposed for methotrexate, is stressed as a general sample cleanup procedure for liquid chromatography of highly polar drugs, and was validated for two more applications: teicoplanin and ganciclovir. A dedicated "prevalidation" experimental design was used to assess performances of both assays, including sample preparation. Deviations from linearity were less than 10% over the ranges of 3.1 to 50 mg/l (teicoplanin) and 0.2 to 15 mg/l (ganciclovir), respectively, and limits of quantitation were 0.09 and 0.01 mg/l, respectively. Mean chromatographic measurement R.S.D.s were 4.6% and 1.9%, respectively, with an additional mean cleanup R.S.D. of 2% for both. Mean analyte losses ascribable to cleanup were 6% and 2.5%, respectively from water, and 18% and 12%, respectively from the plasma matrix. (C) 1998 Elsevier Science B.V.