Determination of some antirheumatics by capillary isotachophoresis.

Isotachophoresis (ITP) was applied for the determination of some antirheumatic drugs (fenoprofen, naproxen, ibuprofen, and ketoprofen) in human serum. The leading electrolyte contained hydrochloric acid (10 mmol x L(-1)), creatinine (pH 4.5) and methylhydroxyethyl cellulose (0.1%). The terminating electrolyte was 2-(N-morpholino)ethanesulfonic acid (10 mmol x L(-1)) adjusted with tris(hydroxymethyl)aminomethane to pH 6.9. The ITP separations were carried out in column-coupling configuration of the separation unit provided with a preseparation column of 160 x 0.8 mm inner diameter (ID) and analytical column of 160 x 0.3 mm ID. The limit of detection for ibuprofen, fenoprofen, and naproxen in serum by direct sampling was 0.008, 0.005 and 0.004 mmol x L(-1). The limit of detection for ketoprofen in serum after ethanol precipitation was 0.001 mmol x L(-1).