Abstract
In order to determine the trace amount of Co in iron and steel, the formation of the chelate of nitroso-R salt and Co [Co-NRS] and the extraction of this chelate into a chloroform solution with amines were studied.
Co-NRS chelate was formed at pH 5-7 in the presence of sodium citrate and extracted quantitatively into a chloroform solution by adding tri-n-octylamine [TOA]. The absorbance of Co-NRS chelate in TOA-chloroform solution should be measured at a wave length of approximate 550nm to avoid the reagent blank. NRS chelates of other elements could be decomposed completely by adding H2SO4 into a color developing solution and under this condition the fourteen elements coexisted in iron and steel did not interfere in the determination of Co.
The coefficients of variation as the reproducibilities of this method were 1.2% and 2.1% for 0.23% and 0.03% in Co content respectively and the analytical results of the standard samples agreed well with their corresponding certified values. Because of the simplicity of the analytical procedures, the present method was suitable for the routine analysis.
