铟是一种银白色稀有稀散金属, 在地壳中的平均质量分数为0.000 01%, 为了准确测定烟道灰样品中低含量的铟, 通过对样品成分的初步分析, 确定实验中溶解样品所用的酸及其比例。 依次逐步加入HCl, HNO3, HF和HClO4(V∶V∶V∶V=15∶5∶2∶2), 将样品完全溶解后, 冷却至室温并移入分液漏斗, 在HBr介质中, 以溴化铵做盐析剂(溶液体积控制在25 mL左右); 移取25 mL乙酸乙酯作为萃取剂和稀释剂, 萃取液直接导入配备有机进样系统的电感耦合等离子体原子发射光谱仪(ICP-AES), 选择In 230.606 nm为分析谱线, 对烟道灰样品中的铟进行测定, 从而建立了电感耦合等离子体原子发射光谱法(ICP-AES)测定烟道灰样品中铟的方法。 实验样品溶解后, 采用萃取分离法消除基体元素及共存元素的干扰。 通过对萃取酸度、 萃取剂、 萃取方法、 盐析剂、 分析谱线等条件试验, 确定了最优的实验条件。 铟的质量浓度在0.25~4.00 mg·L-1范围内与其发射强度呈线性关系, 校准曲线线性相关系数为0.999 3, 检出限为0.03 mg·L-1, 测定结果的相对标准偏差(n=11)小于5%, 回收率在92%~102%之间。 按照上述试验步骤测定5个烟道灰样品中的铟含量, 其测定结果与ICP-MS法比较吻合。 另外, 与现有的分析方法(EDTA滴定法、 分光光度法、 原子吸收光谱法、 X射线荧光光谱法、 电感耦合等离子体原子发射光谱法及质谱法等)相比, 该法具有简便, 快速, 灵敏, 准确度较高的优点, 可用于铟含量在0.000 8%~0.10%之间烟道灰样品的批量检测。

Indium is a silver-white rare and scattered metal with an average mass fraction of 0.000 01% in the earth’s crust. In order to accurately determine the low content of indium in the flue ash sample, we preliminarily analyzed the composition of the sample to ascertain the dissolved acid and its proportion in our work. The hydrochloric, nitric, hydrofluoric and perchloric acids (Ｖ∶Ｖ∶Ｖ∶Ｖ=15∶5∶2∶2) were successively and gradually added to completely dissolve the sample, and then cooled to room temperature and transferred into a shunt funnel. Following, the above-obtained mix was diluted with ammonium bromide as salt precipitator (the volume of solution was controlled to about 25 mL), and ethyl acetate as an extractant and diluents. The extraction solution was directly introduced into the inductively coupled plasma atomic emission spectrometry (ICP-AES) equipped with an organic injection system to determine the indium with the analytical spectral line 230.606 nm in the flue ash sample. Thus the method for determination of indium in the flue ash sample by ICP-AES was established. In this work, an extraction separation method was to eliminate the interference of matrix elements and coexisting elements after the sample was dissolved. The optimal experimental conditions were obtained through a series of conditional experiments on extraction acidity, extractant, extraction method, salt analyzer and analytical spectral line. The mass concentration of indium was linear with its emission intensity in the range of 0.25 to 4.00 mg·L-1 with the linear correlation coefficient 0.999 3 and the detection limit 0.03 mg·L-1. The relative standard deviation of the determination results (n=11) was less than 5%, and the recovery rate was 92%~102%. The determination results of indium in five flue ash samples were relatively consistent compared with inductively coupled plasma mass spectrometry (ICP-MS) method according to the above experimental steps. Moreover, this method would be used for batch detection of flue ash samples with indium content between 0.000 8% and 0.10% because of its simple, fast, sensitive, and higher accuracy advantages compared with existing analytical methods (EDTA titration, spectrophotometry, atomic absorption spectroscopy, X-ray fluorescence spectroscopy, inductively coupled plasma atomic emission spectroscopy, mass spectrometry, etc.).