1989 Volume 38 Issue 11 Pages 632-635
A simple, sensitive and specific method for the simultaneous determination of mefenamic and flufenamic acids used as anti-inflammatory drugs in human serum by HPLC with electrochemical detection has been developed. To a 20 μl serum sample, 0.9 ml of 0.01 M phosphate buffer solution (pH 5.6) and 8.33 ng of N-phenylanthranilic acid as an internal standard were added. Serum proteins were precipitated with 1 ml of acetonitrile. After centrifugation, the supernatant was concentrated under reduced pressure to dryness using a concentrator with a trap cooled to -70°C. The residue was dissolved in 90 μl of methanol, and 3 μl of that solution were injected onto the column packed with Shimpack CLC-ODS. The elution was performed with a mixed solvent of 1000 ml of 85% methanol containing 0.05 M sodium perchlorate as the supporting electrolyte, and 5.7 ml of glacial acetic acid. The flow rate was 0.6 ml/min. The potential of the glassy carbon as the working electrode was maintained at +1000 mV vs. Ag/AgCl. The recovery of both drugs added to the control serum was satisfactory. The detection limits for mefenamic and flufenamic acids, at a signal-to-noise ratio of 3, were 0.4 pg and 6.3 pg, respectively. The application of the present method to healthy human serum showed mefenamic acid concentrations ranging from 1.2 to 7.5 μg/ml, and flufenamic acid 6.4 to 14.4 μg/ml following the oral administration of mefenamic (125 mg) and flufenamic acid (100 mg) capsules, respectively.
