High-performance liquid chromatographic separation and indirect fluorescence detection of thiols

A fluorescent post-column reaction detection scheme has been devised for selective determination of thiols. The post-column reagent is 40 μM Cd2+ and 100 μM 8-hydroxyquinoline-5-sulfonic acid (HQS) in non-complexing buffer at pH 10. HQS complexes Cd2+ to form a fluorescent product. Thiols in the HPLC effluent compete for complexation of the Cd2+, resulting in a decrease in the fluorescence response. Detection limits of 0.2 μM (0.04 ppm) are achieved for cysteine, homocysteine and glutathione in a 5 min separation. Recoveries from spiked synthetic urine samples are 87–120%.