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本文研究了用ICP-AES测定海水中碘的方法。在水溶液中,用HNO_3、H_2O_2或NaNO_2将碘离子氧化为碘分子后,在178.276nm波长测定碘的检出限可由未氧化时的0.037ppm降低到0.0021ppm。检出限的降低是由于挥发性分析物形式碘分子的雾化效率远远大于非挥发性分析物形式的雾化效率。在氧化剂存在时,用直接法测得雾化效率为75—80%。实验中发现在分析海水时,由于氯离子与氧化生成碘的相宜作用,使得谱线强度随时间降低,而且干扰程度取决于H~+浓度的大小。将样品溶液的酸度控制在0.5N以下,干扰作用可忽略。对于大量氯离子共存的样品,选用H_2O_2、NaNO_2作为氧化剂更为合适。实验中还发现,碘分子气溶胶记忆效应比较严重,但可通过设计合理的样品输运系统使其减小。
In this paper, ICP-AES was used to determine iodine in seawater. The detection limit of iodine at the wavelength of 178.276nm can be reduced from 0.037ppm to 0.0021ppm when the iodine ion is oxidized to iodine with HNO3, H202 or NaNO2 in aqueous solution. The lower limit of detection is due to the fact that the atomization efficiency of iodine molecules in the form of volatile analytes is much greater than the atomization efficiency in the form of non-volatile analytes. In the presence of oxidant, the atomization efficiency measured by direct method is 75-80%. In the experiment, it was found that in the analysis of seawater, the intensity of the line decreased with the time due to the suitable action of chloride ions and oxidation to form iodine, and the degree of interference depends on the concentration of H ~ +. The acidity of the sample solution is controlled below 0.5N, the interference effect is negligible. For a large number of chloride ion coexistence of samples, the choice of H_2O_2, NaNO_2 as the oxidant is more appropriate. The experiment also found that the iodine molecular aerosol memory effect is more serious, but can be reduced by designing a reasonable sample transport system.