碳酸钠-氧化锌半熔电感耦合等离子体质谱法测定地球化学样品中的碘

Determination of Iodine in Geochemical Samples by ICP-MS with Sodium Carbonate-Zinc Oxide Semi-melting

应用电感耦合等离子体质谱法(ICP-MS)测定地球化学调查样品中的碘,主要采用封闭溶样、混合酸溶、碱熔和半熔法进行样品处理,但由于碘在土壤和沉积物中的存在形态较为复杂,有高碘酸根、碘酸根、碘离子,且碘为卤族元素,第一电离能较高,在样品处理及上机测定环节中存在溶出不彻底、记忆效应强、稳定性较差等问题。本文采用碳酸钠-氧化锌半熔法处理样品,乙醇-沸水提取后用732型阳离子交换树脂将溶液中大量阳离子分离,采用内标法ICP-MS测定样品溶液中的碘。通过优化溶样程序提升了样品溶出效果,优化测定介质及内标元素消除记忆效应,提升了结果稳定性,建立了一套完善的ICP-MS测定碘的方法。使用土壤和沉积物国家一级标准物质进行方法验证,方法检出限为0.045μg/g,方法检测下限为0.15μg/g,方法精密度(RSD,n=12)≤5.93%,方法准确度△logC≤0.01,符合地球化学调查样品分析测试要求,可推广应用于地球化学调查中大批量土壤和沉积物样品的分析测试。

BACKGROUND:The determination of iodine in geochemical samples by inductively coupled plasma-mass spectrometry(ICP-MS)is treated mainly by closed sample melting,mixed acid solution,alkali fusion and semi-melting method.However,due to the complex existent morphology of iodine in soil and sediment samples,including periodate,iodate and iodide ions,and the first ionization energy of iodine being high as a halogen group element,there are problems such as incomplete dissolution,strong memory effect and poor precision during sample processing and measurement.OBJECTIVES:To improve the determination of iodine in geochemical samples by ICP-MS.METHODS:The samples were treated by sodium carbonate-zinc oxide semi-melting method,extracted with boiling water-ethanol,and separated by 732 cation exchange resin.Following this,iodine in the solution was determined by ICP-MS using an internal standard method.RESULTS:The optimized detection limit of iodine was 0.045μg/g,the lower limit of detection was 0.15μg/g.The precision(RSD,n=12)and the accuracy(△logC)of the method were≤5.93%and≤0.01,respectively,which satisfied the analysis standards of geochemical survey sample.CONCLUSIONS:This method meets the requirements of sample analysis for geochemical investigation,and can be used for the analysis of iodine in large quantities of soil and sediment samples.