Rapid serum vancomycin assay by high-performance liquid chromatography using a semipermeable surface packing material...

A new isocratic high-performance liquid chromatographic (HPLC) assay has been developed for vancomycin that uses direct injection of microquantities of serum into a separation column filled with octyl-C(8) silica support that has a semipermeable surface. A mixture of disodium hydrogen phosphate buffer (pH 7.0) and acetonitrile is used as the mobile phase, and vancomycin is directly detected at 240 nm. The minimum limit of detection was 0.5 microg/ml at a signal-to-noise ratio of 3:1. Linearity was established from 0 to 100 microg/ml. The coefficient of variation for within-run reproducibility was 1.1-2.7% for a concentration range of 2.9-52.5 microg/ml; for day-to-day reproducibility it was 4.0% and 3.1% for a concentration range of 5.8-26.4 microg/ml, and the recovery rate was 94-105%. There was no interference from 41 antibiotics or other drugs currently in use. The correlation coefficient between the fluorescence polarization immunoassay (x) and this method (y) was 0.995 with a linear equation, y = 1.06x - 0.924. This method is simple, rapid, and provides an economical quantification of serum vancomycin.