Spectrophotometric Flow Injection Analysis of Silicates for Manganese

Abstract

A flow injection spectrophotometric method has been developed for the determination of manganese in silicate rocks with formaldoxime as a chromogenic reagent. A rock solution is prepared by fusion with a mixture of lithium carbonate and boric acid and subsequent dissolution of the cake in 1 M hydrochloric acid. An aliquot of the sample solution is treated with hydrofluoric and perchloric acids and passed through a cellulose phosphate column to remove polyvalent cations like iron(III) and aluminum(III). A definite portion of the filtrate is injected into the flow system where the manganese-formaldoxime complex allows to be formed and monitored at 452 nm. Nickel is masked with 2-aminoethanethiol by a merging zone technique. The flow injection analysis system permits throughput of 45 samples per hour. The relative standard deviations (n=10) for 0.5 and 2.0 ppm manganese solutions are 0.80 and 0.33%, respectively. The procedure has been applied to a variety of standard silicate rocks of the U.S.Geological Survey and of the Geological Survey of Japan, yielding the results which are in satisfactory agreement with the recommended or reported values.