Determination of ibuprofen and naproxen in tablets.

Ibuprofen and naproxen have been quantified in tablets by capillary isotachophoresis. Hydrochloric acid (10 mmol/l) adjusted with creatinine to pH 5.0 plus 0.1% polyvinylpyrrolidone was used as the leading electrolyte and 10 mmol/l 4-morpholineethanesulfonic acid as the terminating electrolyte. Linearity was observed from 40.0 to 200.0 mg/l of ibuprofen (naproxen), with a coefficient of determination (r2) of 0.999. Good quantitation was obtained in short analysis time. The isotachophoretic results were compared with those obtained by the fluorescence spectrometry. Experimental parameters for ibuprofen were: lambdaEX=224 nm and lambdaEM=290 nm. Experimental parameters for naproxen were: lambdaEX=230 nm and lambdaEM=355 nm. The calibration plot was found to be linear in the range 0.4-2.4 mg/l for ibuprofen and 5.0-20.0 microg/l for naproxen. The minimal sample pretreatment and relatively low running cost make isotachophoresis a good alternative to existing methods.