Determination of methamphetamine in urine samples with sodium 1,2-naphthoquinone-4-sulphonate

Abstract

Optimal conditions have been studied for the determination of methamphetamine in urine samples by an extractive-spectrophotometric method with sodium 1,2-naphthoquinone-4-sulphonate (NQS) as reagent. These conditions are: NaHCO3 pH 10, NQS 6.3 × 10−3 mol/l and heating for 5 min at 45°C. The accuracy and precision of the method were tested. The detection limits were 0.2 mg/l in the standard and 0.9 mg/l when 5 ml of urine sample were taken. The standard deviation of blank urine was evaluated from 12 different samples. The relative errors found in the determination of methamphetamine in urine were lower than 10% if the methamphetamine-amphetamine ratio was higher than 4.