Selective determination of 4-aminobenzoic and 4-aminosalicylic acid derivatives in mixtures by flow-injection analysis

The working conditions were found for the determination of medicinal substa nces anesthesin (benzocaine, I), novocaine (II), novocainamide (procainamid e, III), and sodium 4-aminosalicylate (IV) as their 4,6-dinitrobenzofuroxan derivatives by flow-injection analysis with spectrophotometric detection ( lambda 510 nm). The best conditions were attained using a mixture of ethano l (methanol) and a buffer solution of pH 6.68 (30 : 70 vol %). The analytic al range for the analytes was 0.08-5.0 mu g/mL. The detection limits (3 sig ma, n = 4) were 0.04 (I), 0.05 (II), 0.07 (III), and 0.03 (IV) mu g/mL. Pro cedures for determining 4-aminobenzoic and 4-aminosalicylic acid derivative s in pharmaceuticals containing ephedrine, atropine, dimedrol, and inorgani c salts and in biological fluids (protein hydrolyzate, blood plasma, and wh ole blood) were developed.