On-line removal of sulfide interference in phosphate determination by flow injection analysis

Abstract

Simple on-line sulfide removal using potassium permanganate (KMnO 4) was incorporated into a spectrophotometric flow injection (FI) system for phosphate determination using molybdenum blue with ascorbic acid as the reductant. Excess KMnO 4 was reduced before the sample zone passed through the detector and the method effectively removed all sulfide interference. Without this removal, sulfide interference caused major errors in filterable reactive phosphorus (FRP) analyses. Some model organic phosphates were tested with the permanganate manifold and there was no conversion to phosphate. With the KMnO 4 carrier, the calibration plot was linear over the tested range (0-1000 μg L -1 P), with a de..