双环己酮草酰二腙分光光度法测定锰铁合金、锰硅合金和金属锰中铜

Determination of copper in ferromanganese,silico-manganese and manganese metal by bisoxaldihydrazone spectrophotometry

锰铁合金、锰硅合金和金属锰中铜在多数钢铁冶炼中属于有害元素,会降低钢材机械性能,加热时导致钢材表面氧化,为此建立了双环己酮草酰二腙分光光度法测定锰铁合金、锰硅合金和金属锰中铜的方法。以硝酸、氢氟酸分解样品,利用高氯酸冒烟提供高温和强氧化作用,硅与氢氟酸反应生成四氟化硅挥发除去,碳被氧化分解或生成微小碳粒达到铜完全释放。在盐酸介质中,以氯化铵-氢氧化铵缓冲溶液(pH 9.2)控制溶液pH值为8.9~9.5,铜在1 min内即可与双环己酮草酰二腙完全生成稳定的螯合物。实验结果表明,通过在系列标准溶液中进行锰、铁基体匹配,同时在系列标准溶液和样品测量溶液中加入柠檬酸作掩蔽剂,并针对不同锰、铁含量的显色溶液配制专门的参比溶液,可以消除锰、铁基体效应的影响。在铜的校准曲线线性范围内,线性相关系数为0.999 1;铜的检出限为0.006 6μg/mL。实验方法用于测定锰铁合金、锰硅合金和金属锰中铜,结果的相对标准偏差(RSD,n=11)为5.4%~9.5%,回收率为97%~105%;按照实验方法测定3个锰铁合金和1个锰硅合金标准样品中铜,结果与认定值相吻合;选择6个实验室进行了验证试验,各实验室间结果基本一致。

Copper in ferromanganese,silico-manganese and manganese metal was a harmful element in most steel smelting processes.It could reduce the mechanical properties of steel and cause oxidation of steel surface in heating.Therefore,a determination method of copper in ferromanganese,silico-manganese and manganese metal by bisoxaldihydrazone spectrophotometry was established.The sample was decomposed with nitric acid and hydrofluoric acid.The perchloric acid smoking was adopted to provide the effect of high temperature and strong oxidation.Under this condition,silicon reacted with hydrofluoric acid to form silicon tetrafluoride and then was removed by volatilization.Carbon was oxidized or decomposed to tiny carbon particles to completely release copper.In hydrochloric acid medium,the pH of solution was controlled at 8.9-9.5 with ammonium chloride-ammonium hydroxide buffer solution(pH 9.2).Copper could react with bisoxaldihydrazone to form stable chelate within 1 min.The experimental results showed that the matrix effect of manganese and iron could be eliminated under following conditions:the matrix matching of manganese and iron was conducted in the standard solution series;the citric acid was added into standard solution and sample solution as a masking agent;the special reference solution was prepared for the coloring solutions containing different contents of manganese and iron.In the linear range of calibration curve for copper,the linear correlation coefficient was 0.999 1.The detection limit of copper was 0.006 6μg/mL.The proposed method was applied for the determination of copper in the samples of ferromanganese,silico-manganese and manganese metal.The relative standard deviations(RSDs,n=11)of the results were between 5.4%and 9.5%,and the recoveries were between 97%and 105%.The content of copper in three certified reference materials of ferromanganese and one certified reference material of silico-manganese was determined.The results were consistent with the certified values.Six laboratories were selected for the verification test,and the results were basically the same.