Flow Injection Spectrophotometric Determination of Sulphide by Catalytic Reduction of Toluidine Blue

Abstract

<em>Sulphide was determined spectrophotometrically at 628 nm and pH 6.7 based on its catalytic reduction of toluidine blue in the presence of Se(IV) using a flow injection system. After optimization of the measuring conditions the calibration curve was found linear up to 25 </em><em>m</em><em>g/mL and the detection limit was 0.3 </em><em>m</em><em>g/mL (30 </em><em>m</em><em>L injections). The relative standard deviation for the determination of 10 </em><em>m</em><em>g/mL sulphide was 1.2% (n=14). The injection rate was 30 h^-1.</em>