Determination of Unbound Dicloxacillin in Human Plasma by Hollow Fiber Centrifugal Ultrafiltration

OBJECTIVE To establish a novel method combining hollow fiber centrifugal ultrafiltration and HPLC for determination of unbound dicloxacillin in human plasma. METHODS Hollow fiber centrifugal ultrafiltration was employed for the pretreatment of plasma samples. The Kromasil C₁₈ column was used for HPLC analysis. The chromatographic conditions were as follows, mobile phase was acetonitrile-25 mmol·L^-1 phosphate solution (pH 4.5)=40:60; flow arte was 1.0 mL·min^-1; detection wavelength was 225 nm; column temperature was 20℃. RESULTS Unbound dicloxacillin showed good linear relationship in the range of 64.0-4096.0 ng·mL^-1(r=0.999 9), and the limit of quantification was 32.0 ng·mL^-1. The recovery were 98.8%-100.3% with RSD<1.3%. CONCLUSION The method is simple, rapid, specific and sensitive. It provides a new reliable means for determination of unbound dicloxacillin.