Spectrophotometric Determination of Trace Amounts of Boron in High-Purity Iron and Ferroalloy after Chemical Separation

Abstract

It is known that impurity elements in steel and other feeds exert an influence on the material characteristics. It is known that boron has a large influence on hardening and brittleness of iron even if a small amount of pole exists, and is requested a accurate quantitative analysis of with good repeatability. Boron is sensitively determined by spectrophotometry after color development with curcumin. However the blank value is high. Therefore, methanol and acids used for the analysis are refined, water is added in addition after color development, and the blank value has been decreased. As a result, the blank value decreased from 0.35 to 0.05 μg and the detection limit of boron became 0.01 ppm. Then, trace amount of boron in high purity electrolysis iron (mairon HP) became 0.24±0.01 ppm by using this method. The separation of B from the matrix is possible hardly receiving the influence of the coexistence element. However, there are little examples of investigation on the recovery of boron by co-precipitation. Si was selected us an element to check the influence in this report. In addition, application of separation procedure to the Fe-Cr-Si alloy was performed. The decrease at the recovery of boron was admitted that the amount of Si in the solution exceeded 25 mg. Then, the Fe-Cr-Si alloy was taken, in which the amount of Si should not exceed 25 mg, and boron in the alloy was determined As a result, it was possible to measure in the change coefficient (C.V) 3.1%.