High‐pressure liquid chromatographic analysis of antipyrine in small plasma samples

Abstract A high‐pressure liquid chromatographic (HPLC) method was developed for the assay of antipyrine in small (0.1‐ml) plasma samples using aminopyrine as the internal standard and a reversed‐phase microparticulate column. The assay sensitivity (1 μ/ml) permits development of a plasma level‐time curve using a single rat. The mean (±  SE ) plasma elimination half‐life in rats was 1.28 ± 0.14 hr. A comparison of the spectrophotometric method with the HPLC method yielded a correlation coefficient of 0.98. The HPLC assay for antipyrine is rapid and precise and can be used for hepatic drug metabolism study in a single animal.