Dithiofluorescein Explained

Dithiofluorescein (sometimes generically called thiofluorescein) is a complexometric indicator used in analytical chemistry. It changes from blue to colorless when it binds to mercury(2+) ions.^[1] It thus can indicate the endpoint in the titration of thiols using o-hydroxymercuribenzoic acid^[2] or its sodium salt.^[3] The reagent can be immobilized t in a polymer on a fiber optic, which might allow development of a detector for sulfide ions in a flow cell.^[4] Unlike fluorescein and other related fluoran dyes that have oxygen substituents on the benzene rings, dithiofluorescein, which has sulfur substituents, is not fluorescent.^[5]

Notes and References

1. Determination of thiol esters with o-hydroxymercuribenzoic acid . Mieczysław . Wroński . Analyst . 19 . 2 . 745–746 . 1966 . 10.1039/AN9669100745 .
2. Talanta . 24 . 6 . 1977 . 347–354 . Analytical applications of o-hydroxymercuribenzoic acid, dithiofluorescein and mercurated fluorescein . Mieczysław . Wroński . 10.1016/0039-9140(77)80019-2 . 18962100 .
3. The determination of thiomalic acid . V. . Chromý . V. . Svoboda . Talanta . 10 . 10 . 1109–1111 . 1963 . 10.1016/0039-9140(63)80152-6 .
4. Analyst . Flow cell studies with immobilised reagents for the development of an optical fibre sulphide sensor . 1986 . Ramaier . Narayanaswamy . Fortunato III . Sevilla . 111 . 9 . 1085 . 10.1039/AN9861101085 .
5. Book: Handbook of Fluorescence Spectroscopy and Imaging: From Ensemble to Single Molecules . Markus . Sauer . Johan . Hofkens . Jörg . Enderlein . 2.2. Organic Fluorophores . 35–38 . 2011 . 978-3-527-31669-4 .