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Abstract
An improved reversed-phase High-Performance Liquid Chromatographic (HPLC) method using UV detection, at 282 nm, is described for the determination of tolfenamic acid in the presence of caffeine, as internal standard, in pharmaceutical preparations and biological fluids. Sample analyses are performed with a Lichrosorb-RP18, 10 μm, 250×4 mmLD., column using acetate buffer, (pH 4.6 and constant ionic strength 0.05 M) methanol (18:82) as eluent, at a flow rate of 1.9 ml/min. The retention time is 1.44 min for caffeine and 2.62 min for tolfenamic acid. The absolute detection limit is 0.5 ng in the presence and 0.9 ng in the absence of internal standard and linearity is observed up to 100 ng injected. The method involves the use of solid