Determination of naproxen in human urine by solid-phase microextraction coupled to liquid chromatography

An SPME–LC–UV method for the determination of the non-steroidal anti-inflammatory drug (NSAID) naproxen and, after hydrolysis, its glucuronide in human urine samples was developed for the first time using a carbowax/templated resin (CW/TPR-100)-coated fibre. The procedure required a very simple sample pre-treatment, an isocratic elution, and provides a highly selective extraction. All the aspects influencing adsorption (extraction time, temperature, pH and salt addition) and desorption (desorption and injection time and desorption solvent mixture composition) of the analyte on the fibre have been investigated. The linear range investigated in urine was 0.2–20 μg/ml (that covers the typical naproxen urinary concentration) and almost quantitative recoveries were obtained. Within-day and between-days R.S.D.% in urine were 4.5 and 6.0, respectively. The LOD and LOQ in spiked urine were 0.03 and 0.20 μg/ml, well below the usual naproxen urinary level.