Determination of 3-mercaptolactic acid by amino acid analyzer after aminoethylation

A quantitative determination of 3-mercaptolactic acid was performed after its conversion into S-aminoethylmercaptolactic acid by reacting with excess of 2-bromoethylamine. S-aminoethylmercaptolactic acid was quantitated by an amino acid analyzer. Other thiols were shown not to interfere with the determination of 3-mercaptolactic acid. The sensitivity of the method was at the nanomoles level. The application of the method to the determination of 3-mercaptolactic acid in human urine is also reported.