微波消解-电感耦合等离子体质谱(ICP-MS)法测定黑土地地表基质调查样品中碘

Determination of Iodine in Black Soil Surface Matrix Survey Samples by Inductively Coupled Plasma Mass Spectrometry(ICP-MS)with Microwave Digestion

碘是活跃元素,价态多,各价态间易相互转化,使其具有熔点低、易挥发,严重记忆效应的独特性质,其分析一直是个挑战。传统方法如半熔法、高压密闭法等存在操作难度大、消解时间长、工作效率低等问题。通过采用硝酸-氢氟酸微波消解处理样品,并利用电感耦合等离子体质谱(ICP-MS)法测定碘含量,克服了传统碘分析方法的一系列问题。研究了不同酸体系和赶酸时间对样品分解效率和挥发损失的影响,同时验证了不同冲洗液对降低碘记忆效应的效果。在此基础上,确定了最佳反应条件为7 mL硝酸+1 mL氢氟酸混合酸比例,180℃赶酸控温程序,并采用2%NH_(3)·H_(2)O充当冲洗液,降低了ICP-MS测定过程中的记忆效应,提高测试的稳定性。为验证该使用国家一级标准物质对方法的准确性和精密度进行验证,结果表明,方法的准确度(Δlgc)为0.001~0.004,相对标准偏差(RSD)为1.2%~3.4%,相关系数为0.9998,检出限为0.17 mg/kg,定量限为0.54 mg/kg,表现出较好的准确度和精密度,满足规范要求。通过实际样品测试,进一步验证了方法的可行性,实验结果表明,相对偏差在1.6%~4.1%。方法操作方便、试剂用量少、工作效率高,适用于测定黑土地地表基质调查样品,同时也为碘的快速、准确分析提供了一种可行的解决方案。

Iodine is an active element with many valence states,which are easy to convert to each other,so it has a unique property of low melting point,volatile,and serious memory effect.Its analysis has always been a challenge.Traditional methods such as semi-melting method and high pressure sealing method have some problems such as difficult operation,long digestion time and low working efficiency.A series of problems of traditional iodine analysis methods were overcome by using microwave digestion of nitric acid-hydrofluoric acid and determination of iodine content by inductively coupled plasma mass spectrometry(ICP-MS).The effects of different acid system and time on sample decomposition efficiency and volatilization loss were studied,and the effect of different rinsing solution on reducing iodine memory effect was verified.On this basis,the optimal reaction conditions were determined as the mixed acid ratio of 7 mL nitric acid and 1 mL hydrofluoric acid,the acid temperature control program at 180℃,and 2%NH_(3)·H_(2)O was used as the flushing solution,which reduced the memory effect during ICP-MS determination and improved the stability of the test.In order to verify the accuracy and precision of the method,the national first-class standard material was used to verify the method.The results showed that the accuracy(Δlgc)of the method was 0.001—0.004,the relative standard deviation(RSD)was 1.2%—3.4%,the correlation coefficient was 0.9998,the detection limit was 0.17 mg/kg,the quantitative limit was 0.54 mg/kg,showing good accuracy and precision,and meeting the specification requirements.The feasibility of this method was further verified by the actual sample test,and the experimental results showed that the relative deviation was in the range of 1.6%—4.1%.The method is easy to operate,with less reagent and high working efficiency.It is suitable for the determination of black soil surface matrix survey samples,and also can provide a feasible solution for the rapid and accurate analysis of iodine.