Spectrofluorimetric Determination of Submicrogram Silicate with Benzoin and Mannitol

Abstract

A method for the determination of 5ng-10μg (as Si) of silicate based on the formation of a fluorescent complex among silicate, benzoin and mannitol in a strongly alkaline formamide medium has been established. To reduce the blank value and to improve the reproducibility, sodium dithionite is added as a reducing agent; this prevents the oxidation of benzoin. The silicate in the solution can be determined over a very wide range by the same chemical procedures only by changing the sensitivity range of the spectrofluorimeter. The relative standard deviation of the method at a level of 0.5μg Si is 2.7%. Phosphate and arsenate can be tolerated up to 4000-fold amounts.