Determination of salicylate in blood serum by flow injection with immobilized salicylate hydroxylase

A flow injection (FI) enzymatic system, based on the use of immobilized sal icylate hydroxylase in glass beads, was developed for the determination of salicylate. Salicylate hydroxylase and nicotinamide adenine dinucleotide (N ADH) are used to convert salicylate to catechol. The reaction of catechol w ith 4-aminophenol at high pH yields a colored product which is detected spe ctrophotometrically at 565 nm. Ten samples of human serum containing from 5 .0 x 10(-4) to 5.0 x 10(-3) mol/L added salicylate were analyzed and the re covery was determined. Eight additional serum samples containing salicylate were analyzed by the Trinder test and the proposed method. The results obt ained with the 2 methods showed good agreement by the statistical Student's t-test. The relative precision of the method is about 3.4% (RSD of the mea n recovery). Considering the lowest concentration analyzed, the quantitativ e limit of detection is about 0.2 x 10(-5) mol/L (3 x SD). The volume of th e sample used was 150 muL. The proposed method was also used to analyze med icines containing acetylsalicylic acid. The results were statistically comp ared with those obtained through the U.S. Pharmacopoeia procedure and showe d excellent agreement.