火焰原子吸收光谱法测定锌精矿中铟

锌精矿中铟含量是贸易结算的重要指标,准确测定锌精矿中铟含量具有重要的指导意义。以盐酸-氟化铵-硝酸-硫酸溶解样品,在盐酸(1+19)介质中,使用空气-乙炔火焰,以303.9 nm为测定波长,建立了火焰原子吸收光谱法测定锌精矿中0.002 0%～0.120%(质量分数,下同)铟的方法。溶样试验表明,对于碳含量较低的样品,采用20 mL盐酸-0.2 g氟化铵-5 mL硝酸-5 mL硫酸可将样品溶解完全;若溶样后溶液有黑渣,说明样品中碳含量较高,则需再继续加入2 mL高氯酸进行溶样。考察了锌基体对测定的影响。结果表明,当锌基体质量浓度大于3.25 mg/mL时,锌基体对测定的干扰较为显著;当锌基体质量浓度不大于3.25 mg/mL时,锌基体对测定的干扰可忽略。对于不同铟含量的样品,实验采用不同的方法进行处理以消除锌基体对测定的干扰。对于高含量的铟(0.050%~0.120%),采取溶样后将溶液体积稀释为原来的2倍后直接测定的方法;对于低含量的铟(0.002 0%~0.050%),须在溶样后先采用乙酸丁酯对铟进行萃取分离再进行测定。干扰试验表明,无论是测定高含量铟还是低含量铟,样品中的其他共存元素均不干扰测定;测定液中残留的少量硫酸和硝酸均对测定无干扰。实验表明,铟的质量浓度在0.50～10.00 μg/mL范围内与其对应的吸光度呈线性关系,相关系数为0.999 7,方法检出限为0.088 μg/mL,定量限为0.29 μg/mL。采用实验方法对锌精矿样品中的铟进行测定,结果表明,高、低铟含量水平的测定结果分别与萃取分离分光光度法或电感耦合等离子体原子发射光谱法(ICP-AES)基本一致,相对标准偏差(n=11)为2.1%～5.2%。

Determination of indium in zinc concentrate by flame atomic absorption spectrometry

Indium content in zinc concentrate is an important index for trade settlement. The accurate determination of indium content in zinc concentrate has important guiding significance. The sample was dissolved with hydrochloric acid, ammonium fluoride, nitric acid, and sulfuric acid. A method for determination of indium content in range of 0.002 0%-0.120% (mass fraction, similarly hereinafter) in zinc concentrate was established by flame atomic absorption spectrometry (FAAS) at 303.9 nm with air-acetylene as flame and hydrochloric acid (1+19) as determination medium. The sample dissolution tests showed that the sample with relatively low carbon content could be fully dissolved with 20 mL of hydrochloric acid, 0.2 g of hydrochloric acid, 5 mL of nitric acid, and 5 mL of sulfuric acid. If there was black residue in solution, it indicated that the carbon content in sample was relatively high, and 2 mL of perchloric acid should be further added for sample dissolution. The influence of zinc matrix on determination was investigated. The results showed that the interference of zinc matrix with determination was relatively significant when the mass concentration of zinc matrix was higher than 3.25 mg/mL. The interference of zinc matrix with determination could be ignored when the mass concentration of zinc matrix was not higher than 3.25 mg/mL. For the samples with different indium contents, different treatment methods were used to eliminate the interference of zinc matrix with the determination. When the indium content was high (0.050%-0.120%), the volume of solution after sample dissolution was diluted to twice for direct determination. When the indium content was low (0.002 0%-0.050%), the extraction separation of indium by butyl acetate should be conducted before determination. The interference tests indicated that other coexisting elements in sample did not interfere with determination whether for determination of high content or low content of indium, and the residual sulfuric acid and nitric acid in test solution had no interference with determination. The experimental results showed that the mass concentration of indium in range of 0.50-10.00 μg/mL had linear relationship with its corresponding absorbance. The correlation coefficient was 0.999 7. The limit of detection and limit of quantification was 0.088 μg/mL and 0.29 μg/mL, respectively. The experimental method was applied to the determination of indium in zinc concentrate sample, and the results were consistent with those obtained by spectrophotometry after extraction separation or inductively coupled plasma atomic emission spectroscopy (ICP-AES) for the sample with high content or low content indium, respectively. The relative standard deviations (RSD, n=11) were between 2.1% and 5.2%.