A Sensitive Gas-Chromatographic Assay Using a Nitrogen-Phosphorus Detector for Determination of Antipyrine and Aminopyrine in Biological Fluids

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Abstract
A method using gas chromatography with organic N-sensitive detection is described for measurement of antipyrine and aminopyrine [analgesics and antipyretics] concentrations in biological fluids. The analysis was performed isothermally on 3% SP-2250 DB after alkalinized saliva was extracted into chloroform. Phenacetin served as internal standard. Low oral doses of antipyrine (1.0-1.8 mg/kg) and/or aminopyrine (2 mg/kg) were measured accurately in saliva of normal human subjects. The standard curves for antipyrine and aminopyrine were linear from 0-10 .mu.g/ml. The coefficient of variation, determined at a salivary concentration of 2 .mu.g/ml, was 1.7% for antipyrine and 2.4% for aminopyrine. Saliva concentrations obtained by this method in normal human subjects after an oral dose of antipyrine (18 mg/kg) or aminopyrine (9 mg/kg) agreed with those determined by the flame ionization gas-chromatographic method used to measure higher concentrations of antipyrine and aminopyrine. Antipyrine (1.8 mg/kg) administered concomitantly with aminopyrine (1 or 2 mg/kg) to normal male volunteers prolonged mean saliva antipyrine half-life by .apprx. 25-33% compared to values obtained when these same subjects received the same dose of antipyrine alone.