氢化物发生-原子荧光光谱法测定铬矿中砷

铬矿中砷的测定方法对完善铬矿检测方法和质量评价手段有重要意义。在0.5 g样品中加入2 g过氧化钠,于650 ℃熔融20 min,熔融物经盐酸酸化溶解,以10%盐酸为载流,15 g/L硼氢化钾溶液为还原剂,采用氢化物发生-原子荧光光谱法(HG-AFS)进行测定,建立了铬矿中砷测定的新方法。实验表明,砷质量浓度在0.025～100 μg/L范围内与荧光强度呈线性关系,相关系数为1.000 0,方法检出限为0.05 μg/g,定量限为0.17 μg/g。对产地为南非、土耳其、巴基斯坦等19个国家共2 649个铬矿样品的成分进行统计,发现铬矿主要成分为铬、铁、镁、铝和硅;干扰试验表明,这些样品中的共存元素均不干扰测定。按照实验方法对3个不同砷含量的铬矿样品进行精密度和加标回收试验,结果的相对标准偏差(RSD,n=11)为1.4%～6.0%,回收率为96%~109%。将实验方法应用于与铬矿基体近似的铁矿标准物质中砷的测定,测定值与认定值基本一致。

Determination of arsenic in chromium ore by hydride generation-atomic fluorescence spectrometry

The establishment of method for determination of arsenic in chromium ore is of great significance to improve the detection method and quality evaluation approach of chromium ore. 2 g of sodium peroxide was added into 0.5 g of chromium ore sample, and the mixture was fused at 650 ℃ for 20 min. The melt was acidified and dissolved with hydrochloric acid. A method for the determination of arsenic in chromium ore by hydride generation-atomic fluorescence spectrometry (HG-AFS) was established using 10% hydrochloric acid as the carrier and 15 g/L potassium borohydride as the reducing agent. The experiments showed that the mass concentration of arsenic in range of 0.025-100 μg/L had linear relationship with the corresponding fluorescence intensity. The correlation coefficient was 1.000 0. The limit of detection was 0.05 μg/g, and the limit of quantification was 0.17 μg/g. The composition statistics of 2 649 chromium ore samples from 19 countries including South Africa, Turkey and Pakistan were conducted. It was found that the main elements in chromium ore were chromium, iron, magnesium, aluminum and silicon. The interference tests indicated that the coexisting elements in samples had no interference with the determination. Three chromium ore samples with different contents of arsenic were used for precision and standard addition recovery tests according to the experimental method. The relative standard deviation (RSD, n=11) of determination results were between 1.4% and 6.0%. The recoveries were between 96% and 109%. The proposed method was applied for the determination of arsenic in certified reference materials of iron ore with similar matrix to the chromium ore, and the found results were basically consistent with the certified values.