Enzyme electrode for the determination of salicylate

Salicylate hydorxylase is used with a carbon dioxide sensor for the determination of salicylate in aqueous solution and pooled serum. The enzyme is physically entrapped with a dialysis membrance at the sensing tip of the carbon dioxide electrode. The enzyme catalyses the stoichiometric formation of catechol and carbon dioxide from salicylate and reduced pyridine nucleotide in the presence of flavin adenine dinucleotide as a specific cofactor. The carbon dioxide is detected by the sensor and related to the concentration of salicylate via a calibration curve. The method compares favorably with the spectrophotometric method for assay of salicylate. Although suitable for salicylate concentrations in the range of 5–300 μg ml^?1, its response below 5 μg ml^?1 is limited by the detection limit of the carbon dioxide sensor.