Identification of thiols by means of mercurated fluorescein

A method is proposed for the identification of thiols by examination of their complexes with tetra-acetoxymercurifluorescein (TMF). It is based on the determination of the fluorescence intensity as a function of pH and exciting wavelength, and of absorbance as a function of pH at 465 and 510 mmu. The relative fluorescence of the complexes does not depend on the wavelength of the exciting light in the range 460-500 mmu. The presence of a carboxyl group in the thiol molecule results in a strong increase of fluorescence with increasing pH and an exciting wavelength > 500 mmu.