Method for the biological monitoring of hexahydrophthalic anhydride by the determination of hexahydrophthalic acid in urine using gas chromatography and selected-ion monitoring.

A method for the determination of hexahydrophthalic acid, a metabolite of hexahydrophthalic anhydride, in human urine has been developed. The urine was worked-up by liquid-solid extraction, esterified with boron trifluoride-methanol, and analysed by capillary gas chromatography and selected-ion monitoring. Hexadeuterium-labelled hexahydrophthalic acid was used as the internal standard. The precision was 4% at 0.7 microgram/ml and 5% at 0.07 microgram/ml. The recovery of the acid for the overall method was 101% at 0.07 micrograms/ml of urine (with a coefficient of variation of 4%) and 95% at 0.7 microgram/ml (coefficient of variation 2%). The limit of detection was 20 ng/ml urine.