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 1M 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 452nm. 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 2.0ppm 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.