The coulometric determination of salicylate in serum

Constant-current coulometry can be used for the determination of salicylate in 100 μg of blood serum. The titration is preceded by extraction of acidified serum with ethylene dichloride followed by removal of the salicylate to an aqueous solution of pH 7.5 tris(hydroxymethyl)aminomethane buffer which also contains copper(II) sulfate to enhance recovery. A residual titration with bromine as titrant followed by addition of potassium thiocyanate is used because of the slow bromination of salicylate. Serum samples containing salicylate in the range 4–60 mg/100 ml were analyzed. Recoveries of about 90% were obtained.