Clinical Chemistry, Vol 25, 589-591, Copyright © 1979 by the American Association for Clinical Chemistry

A Liquid-Chromatographic Analysis for Indomethacin in Serum

¹ Service Division, Dept. of Biochemistry, and Research Institute, The Hospital for Sick Children, Toronto, Canada M5G 1X8

We describe a "high-performance" liquid-chromato-graphic assay for measuring indomethacin in 100 µL of serum. The procedure involves an ethylene dichloride extraction of indomethacin and internal standard (2,5-diphenyloxazole) from serum. The organic phase is separated and evaporated, and the residue dissolved in a 40/60 (by vol) mixture of potassium phosphate buffer (10 mmol/L, pH 3.0) and acetonitrile. An aliquot of this solution is injected into the chromatograph. We used a µ-Bondapak C-18 column with the above-mentioned buffer system as mobile phase, a flow rate of 3.0 mL/min, and a column temperature of 40 °C. Indomethacin and the internal standard are detected by their absorbance at 200 nm and quantitated by measuring peak heights. The procedure allows for the reliable analysis for indomethacin in serum at concentrations > 100 µg/L. Analytical recovery for indomethacin was 66-68%, and the method affords good day-to-day precision (CV <11 %).