Fluorometric determination of 2,3-dimercaptopropane-1-sulfonic acid and other dithiols by precolumn derivatization with bromobimane and column liquid chromatography.

The increasing therapeutic use of dithiol metal binding agents, such as 2,3-dimercaptopropane-1-sulfonic acid (DMPS), has stimulated the need for a sensitive and selective method for their determination in biological fluids. A method has now been developed in which DMPS was converted to a highly fluorescent and stable derivative by reaction with bromobimane in aqueous solution at pH 8.3. The reaction was complete within 5 min. The derivative was separated by ion-pair reversed-phase column liquid chromatography. The mass spectrum of the derivative showed that two bromobimane molecules reacted with one DMPS molecule. This method is also applicable to the determination of other dithiols. The detection limit for DMPS in urine is 10 pmol per 20-microliters injection and the precision is 7.4% at the 100-pmol level. The fluorescence response was linear from 1 to 400 micron. This method was used to determine DMPS in the urine of rabbits treated with this metal binding agent. In addition, total DMPS was determined by adding sodium tetrahydridoborate to the same urine to reduce biotransformed and oxidized DMPS.