Spectrofluorimetric determination of thallium in silicate rocks with rhodamine b in the presence of aluminum chloride

A sensitive spectrofluorimetric procedure with rhodamine B in the presence of aluminum chloride is given for determining submicrogram and microgram quantities of thallium in silicate rocks. Samples are decomposed with a mixture of hydrofluoric and nitric acids and then treated with hydrochloric acid. Thallium is extracted as its dithizonate with chloroform from an alkaline medium containing ascorbate, citrate, and cyanide and then back-extracted with dilute nitric acid. After destruction of the organic matter and treatment with bromine, hydrochloric acid, aluminum chloride, and rhodamine B, the

T001. Determination of thallium in U.S. Geological Survey standard rocks by different laboratories

Thallium (p.p.m.)		Method	Ref.
G-1	W-1
1.06	0.102	Neutron activation analysis	1
1.08	0.121, 0.116	Neutron activation analysis	2
1.3	0.17	Neutron activation analysis	3
1.3	0.11	Spectrographic	4
	0.105–0.110	Flameless atomic absorption spectroscopy	5
1.3a	0.13a		19
1.24b	0.110b		20
1.09 ± 0.01	0.110 ± 0.005	Spectrofluorimetric	Present method

a

Values given by Fleischer.

b

Average value given by Flanagan. fluorescence intensity of the benzene-extracted rhodamine B chlorothallate is measured. The limit of determination is approximately 0.01 p.p.m. for a 1.0-g sample. The thallium contents of U.S. Geological Survey standard rocks G-1 and W-1 were found to be 1.09 ± 0.01 and 0.110 ± 0.005 p.p.m., respectively.