Improved and simplified liquid chromatographic assay for adefovir, a novel antiviral drug, in human plasma using derivatization with chloroacetaldehyde

A rapid and simplified chromatographic assay is reported for the quantification of adefovir (PMEA) utilizing derivatization with chloroacetaldehyde. Adefovir is isolated from plasma using protein precipitation with trichloroacetic acid; next, the fluorescent 1,N⁶-etheno derivative is directly formed at 98°C in the buffered extract with chloroacetaldehyde. This derivative is analyzed using isocratic ion-pair liquid chromatography and fluorescence detection at 254 nm for excitation and 425 nm for emission. In the evaluated concentration range (10–1000 ng/ml) precisions ≤5% and accuracies between 95 and 117% were found, using a 0.2-ml volume of plasma. The lower limit of quantification is 10 ng/ml with a intra-assay precision of 16%. The currently reported bioanalytical method is 20–25-fold more sensitive than previously published assays.