High-performance liquid chromatographic measurement of exogenous thiosulfate in urine and plasma

A simple technique using reverse-phase ion-pair liquid chromatography for measurement of exogenous thiosulfate is described. Accurate measurement of thiosulfate in plasma and urine was permitted by precolumn derivatization with monobromobimane, a substance that readily yields fluorescent compounds upon reaction with a variety of biologically important nucleophiles including glutathione, cysteine, and sulfite. Using an injection volume of 50 microliters, as little as 0.16 nmol of thiosulfate was reliably measured. The interassay precision of the method was reflected by a coefficient of variation of 7.7% while the coefficient of variation for interassay analysis was 2.6%. Recovery of thiosulfate from plasma was 96.9 +/- 3.2% and greater than 98% from urine. The simplicity, sensitivity, and precision of the method make it ideal for the study of thiosulfate and other important nucleophiles in body fluids.