Use of p-diethylaminophenylmercuric acetate for the determination of thiol groups in biological samples

A simple titrimetric method for the determination of thiol and disulphide groups in biological samples with p-diethylaminophenylmercuric acetate as titrant, is suggested. Milligram amounts of cysteine (1-25 mg) are determined with a relative standard error not higher than 1%. The lowest detenninable amount of cysteine is 0.1 mg (relative standard deviation 3%). The accuracy and the sensitivity are the same as in amperometric titration with mercuric chloride. The method has been successfully used for the determination of thiol groups in various biological samples.