应用氢化物发生-原子荧光光谱法测定了铁矿石中微量砷.试样用硝酸、盐酸及氟氢酸的混合酸在微波消解仪中消解处理.经试验选定微波消解程序为:① 消解功率650 V;② 以5 ℃·min-1速率升温至170 ℃,保持20 min;③ 冷却20 min,在所得溶液中加入饱和硼酸溶液使游离氢氟酸络合,再加入硫脲及抗坏血酸溶液作掩蔽剂后定容为50 mL,在仪器工作条件下进行砷的测定.设置样品溶液的进样量为1.0 mL,10 g·L-1硼氢化钾溶液的加入量为0.5 mL.在制作标准曲线时加入一定量的铁以抵消基体铁的干扰.砷的质量浓度在0.90~100 μg·L-1范围内与相应的荧光强度之间呈线性关系.方法的检出限(3s)为0.40 μg·L-1.按所提出的方法测定了铁矿石标准样品中砷量,所得结果与认定值相符.

HG-AFS was applied to the determination of arsenic in iron ore.The sample was digested in a microwave sample digestor under the optimized conditions of: ① power for digestion: 650 V;② raising the digestion temperature to 170 ℃ at a rate of 5 ℃·min-1,and keeping for 20 min;and ③ cooling for 20 min.Definite amounts of sat′d boric acid solution and solutions of thiourea and ascorbic acid were added to the sample solution as complexing agents.The sample solution was diluted to 50 mL and used for HG-AFS determination of arsenic under the working condition of the instrument.The preset volumes of injection of sample solution and 10 g·L-1 KBH4 solution were 1.0 mL and 0.5 mL respectively.Definite amount of iron solutions were added to each of the test solutions in the preparation of standard curve in order to match the matrix inteference of iron.Linear relationship between values of fluorescence intensity and mass concentration of arsenic was obtained in the range from 0.90 to 100 μg·L-1,and detection limit (3s) found for the method was 0.40 μg·L-1.The proposed method was applied to the determination of arsenic in standard samples of iron ore,giving results in consistency with the standard values.