Assay of 3-carboxy-antipyrine in urine by capillary gas chromatography with nitrogen selective detection. Some preliminary results in man.

An assay procedure is described for 3-carboxy-antipyrine in urine using gas chromatography with a support coated open tubular capillary column (Carbowax 20M), a solid injection system and nitrogen selective detection. 3-Carboxy-antipyrine was analyzed after derivatization with diazomethane and using 4-bromo-antipyrine as internal standard. Following extraction of the urine samples with a mixture of organic solvents linear calibration curves were obtained in the concentration range of 1--50 microgram/ml. The precision was established as +/- 5.0% (n = 5), and the lowest measurable concentration was 1 microgram/ml at a signal-to-noise ratio of 10:1. Preliminary results in 5 human volunteers showed that after orl administration of 500 mg antipyrine, 3.3 +/- 0.8% of the dose was excreted as 3-carboxy-antipyrine in 52 hours' urine. The compound was excreted completely in the unconjugated form.