1996 Volume 82 Issue 11 Pages 923-928
Manganese at the μg/g level in steel is determined by differential pulse cathodic stripping voltammetry in a strongly acidic sample solution without separating iron matrix. The method is based on the accumulation and subsequent stripping of hydrated manganese (IV) oxide on a platinum disk electrode. Optimum experimental conditions include the use of a 2 ml aliquot of the 0.23 M nitric-0.18 M sulfuric acid mixture electrolyte containing 2 mg of a sample, and pre-electrolysis at +1.45 V vs. SCE followed by a negative-going scan at a rate of 200 mV/s to +0.65 V vs. SCE.
The peak height of manganese decreased with increasing the amount of iron (III) in the electrolyte and increased linearly with pre-electrolysis time until the electrode surface became saturated. The determination range could broaden by using manganese-free acids and longer pre-electrolysis times; thus the calibration graphs were linear between 1.8×10-8 and 1×10-4 M of manganese (II), within 600 s pre-electrolysis, and passed through the origin. Possible interferences are evaluated.
The determination of 2.8 to 4280 μg/g of manganese in steels was achieved with relative standard deviations of less than 6%(n=10) within 15 min. The detection limit is 0.3 μg/g for a pre-electrolysis time of 600 s. The proposed method is more suitable than the commonly used JIS methods (G 1213 and G 1257) for the determination of trace manganese in steel from the viewpoints of simplicity, less experimental skill, rapidity and high sensitivity as well as excellent precision.
