Flow injection analysis of silicate rocks for titanium

Abstract

A flow injection spectrophotometric method has been developed for the accurate, continuous determination of titanium in silicate rocks. A rock sample solution is prepared by fusion with a mixture of lithium carbonate and boric acid and subsequent dissolution of the melt with 1 M hydrochloric acid. The preparation technique is the same as that used for the determination of total iron and aluminium in silicate rocks by flow injection spectrophotometry. An aliquot of the sample solution is injected directly into the apparatus with no pre-treatment. The system consists of the reduction of iron(III) with ascorbic acid and measurement of the absorption of the titanium-diantipyrylmethane (DAM) complex at 388 nm. In spite of the slow reaction of titanium with DAM, satisfactory results are obtained with an appropriate optimised system. This system permits high throughput of 60 solutions per hour. The procedure has been applied to standard silicate rocks of the US Geological Survey and the Geological Survey of Japan. The precision ranges from 0.1 to 0.8% for titanium(IV) oxide contents of 0.2–2.2%.