铬天青S分光光度法测定锰铁合金、锰硅合金、金属锰中铝

铝在锰铁合金、锰硅合金、金属锰中属于有害元素,在后续钢铁冶炼中易形成夹杂物而使钢铁材料变脆,为此建立了铬天青S分光光度法测定锰铁合金、锰硅合金和金属锰中铝的方法。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从而达到铝完全释放。在酸性溶液中加入铬天青S显色剂,然后调节溶液pH值为5.7~6.0,在室温条件下静置30min,即可使铝完全生成稳定的络合物,达到最佳分析效果。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EDTA-Zn作掩蔽剂,并针对不同锰、铁含量的样品显色溶液,以氟化铵络合铝抑制其显色,配制专门的参比溶液,再将测得的吸光度减去试剂空白显色吸光度,可以消除锰、铁基体效应的影响。在铝的校准曲线线性范围内,线性相关系数可达0.9998,铝的检出限为0.0075%,定量限为0.025%。实验方法用于锰铁合金、锰硅合金、金属锰中铝的测定,结果的相对标准偏差(RSD,n=11)为6.3%~8.1%,回收率为94%~107%。按照实验方法测定锰硅合金标准样品YSB C 26605-2013中铝,测定结果与认定值相吻合;向锰硅合金标准样品YSB C 26605-2013中加铝标准溶液配制锰硅合金合成样品,按照实验方法进行测定,结果与参考值基本一致。选择6个实验室按照实验方法对锰铁合金、锰硅合金中铝进行测定,结果的相对标准偏差为2.0%~4.6%,平均值与电感耦合等离子体质谱法基本一致;按照实验方法测定金属锰中铝,测定结果与电感耦合等离子体质谱法相符。

Determination of aluminum in ferromanganese,ferromanganese-silicon and manganese metal by chrome azurol S spectrophotometry

Aluminum belongs to harmful element in ferromanganese, manganese-silicon alloy and manganese metal and easily forms inclusions in subsequent steel smelting which cause brittleness of steel materials. Therefore, the determination method of aluminum in ferromanganese, ferromanganese-silicon alloy and manganese metal by chrome azurol S spectrophotometry was established. The sample was decomposed with nitric acid and hydrofluoric acid. The perchloric acid fuming was employed to provide high temperature and strong oxidation effect. Silicon could react with hydrofluoric acid to form silicon tetrafluoride and then be removed by volatilization. Carbon was oxidized or decomposed to form small carbon particles so that the aluminum in sample could be completely released. The coloring reagent of chrome azurol S was added into acid solution. Then the pH of solution was adjusted to 5.7-6.0. After placing at room temperature for 30min, the aluminum in sample could be fully formed a stable complex, realizing the best analysis effect. The experimental results showed that the influence of matrix effect of manganese and iron could be eliminated under the following conditions: a series of standard solutions were used for the matrix matching of manganese and iron; meanwhile, EDTA-Zn was added into the series standard solution and sample solution as the masking agent; for the sample coloring solution with different contents of manganese and iron, ammonium fluoride was used for the complexation with aluminum to inhibit its coloring, and the special reference solution was prepared; finally, the absorbance of reagent blank was subtracted from the measured absorbance. Within the linear range of calibration curve for aluminum, the linear correlation coefficient was 0.9998. The detection of limit for aluminum was 0.0075% and the limit of quantification was 0.025%. The proposed method was applied for the determination of aluminum in ferromanganese, ferromanganese-silicon alloy and manganese metal. The relative standard deviations (RSD, n=11) were between 6.3% and 8.1%, and the recoveries were between 94% and 107%. The content of aluminum in certified reference material of ferromanganese-silicon alloy (YSB C 26605-2013) was determined according to the experimental method, and the found results were consistent with the certified values. The standard solution of aluminum was added into certified reference material of ferromanganese-silicon alloy (YSB C 26605-2013) to prepare the synthetic samples. The determination results according to the experimental method were basically consistent with the reference values. Six laboratories were selected for the determination of aluminum in ferromanganese and ferromanganese-silicon alloy according to the experimental method. The RSDs of found results were between 2.0% and 4.6%, and the average value was basically consistent with that obtained by inductively coupled plasma mass spectrometry. The content of aluminum in manganese metal was also determined according to the experimental method, and the result was basically consistent with that obtained by inductively coupled plasma mass spectrometry.