电感耦合等离子体质谱法测定复配矿物质及碘化钾、碘酸钾单体中碘的含量

Determination of Iodine in Compound Minerals,Potassium Iodide and Potassium Iodate Monomers by Inductively Coupled Plasma Mass Spectrometry

国家标准GB 5009.267-2020中电感耦合等离子体质谱法(ICP-MS)适用范围覆盖了所有食品,但需要使用四甲基氢氧化铵(TMAH)提取3~4h,时间较长,不适用于复配矿物质和碘化物单体(如碘化钾、碘酸钾)样品分析,因此提出了题示研究。0.2g复配矿物质样品经10mL 4%(体积分数)硝酸溶液超声溶解5~10min并稀释至50mL,分取2.5mL,加入5mL 10%(体积分数,下同)TMAH溶液,用水定容至50mL。0.2g碘化钾、碘酸钾单体样品直接用10%TMAH溶液溶解后用水定容至50mL,测定1.05%(质量分数)碘化钾单体样品和1.3%(质量分数)碘酸钾单体样品时用1%(体积分数,下同)TMAH溶液稀释500倍,测定10%(质量分数)碘化钾单体样品时用1%TMAH溶液稀释5000倍。上述溶液采用ICP-MS测定其中碘的含量。结果表明,改进后的提取方法大大缩短了时间。碘的质量浓度在10.0~50.0μg·L^(-1)内与碘和内标碲的信号强度比值呈线性关系,检出限(3s)为0.02μg·g^(-1)。按照标准加入法进行回收试验,回收率为84.0%~106%,测定值的相对标准偏差(n=6)均小于9.0%。方法用于实际复配矿物质及碘化钾、碘酸钾单体样品分析,测定结果与理论值(声称值)一致。

Inductively coupled plasma mass spectrometry(ICP-MS)in the national standard GB 5009.267-2020had a wide range of applications and covered all food products.However,it required tetramethylammonium hydroxide(TMAH)extraction for 3-4h,which took a long time and was not suitable for the analysis of compound minerals and iodide monomers(such as potassium iodide and potassium iodate).Therefore,the study mentioned by title was proposed.0.2g of the compound mineral sample was dissolved in 10mL of 4%(volume fraction)nitric acid solution by ultrasound for 5-10min and diluted to 50mL.An aliquot(2.5mL)was taken,and 5mL of 10%(volume fraction,the same below)TMAH solution was added.The mixture was made its volume up to 50mL with water.0.2g of potassium iodide or potassium iodate monomer sample was dissolved directly in 10%TMAH solution and made its volume up to 50mL with water.The solution was diluted 500times with 1%(volume fraction,the same below)TMAH solution for determination of 1.05%(mass fraction)potassium iodide monomer samples and 1.3%(mass fraction)potassium iodate monomer samples,and 5000times with 1%TMAH solution for determination of 10%(mass fraction)potassium iodide monomer samples.Iodine in the above solution was determined by ICP-MS.As shown by the results,the improved extraction method greatly shortened the time.Linear relationship between the signal intensity ratio of iodine to internal standard tellurium and mass concentration of iodine was found in the range of 10.0-50.0μg·L^(-1),with detection limit(3s)of 0.02μg·g^(-1).Test for recovery was made by standard addition method,giving results in the range of 84.0%-106%,with RSDs(n=6)of the determined values less than 9.0%.The method was applied to the analysis of actual compound minerals and samples of potassium iodide and potassium iodate monomers,and the determined results were consistent with the theoretical values(claimed values).