Determination of Chromium(III) with Eriochrome Cyanine R by Fourth-Derivative Spectrophotometry

Abstract

Summary A fourth-derivative spectrophotometric determination of chromium(III) with Eriochrome Cyanine R (ECR) was described. The method was based on measuring the fourth-derivative value (D4) at 545 nm. The experimental and instrumental variables (wavelength range, scan speed, band width and order of derivative) were optimized. Under the optimum conditions, the calibration graph fit the equation d4 A/d4 = 3.75 × 105 [Cr(III)] + 0.003 (r=0.9991) and have a relative standard deviation of 1.19%. The method was valid for concentrations between 20 ng/ml and 80 ng/ml of chromium(III). The molar ratio of the formed complex was 1:2 (M:L). The proposed method was successfully applied to the determination of chromium in steel.