微波消解—ICP-MS测定乳粉中碘的含量

Determination of iodine in milk powder by combing microwave digestion with inductively coupled plasma mass spectrometry

目的:建立一种高效、准确的测定乳粉中碘含量的微波消解—电感耦合等离子体质谱仪测试方法。方法:通过加入0.2 mL沉淀剂和5 mL超纯水混匀静置,再加入5 mL硝酸进行微波消解,冷却后先用超纯水定容至35 mL,再按顺序加10 mL氨水、1 mL稳定剂、50μL TritonX-100后定容,从而避免碘损失。结果:方法检出限为0.044 mg/kg,碘含量在质量浓度为0~20μg/L范围内呈良好线性,相关系数为0.9999。相对标准偏差均在5%以下,样品加标回收率为90.2%~107.7%,多种标准物质的测定值与标示值一致。试验测得相同乳粉中碘含量结果与GB 5009.267—2020第一法的相近。结论:该方法具有高效、回收率好、准确的特点,可确保人员安全,降低仪器维护成本。

Objective:This study aimed to establish an efficient and accurate method for the determination of total iodine in milk powder by microwave digestion combining with inductively coupled plasma mass spectrometry(ICP-MS).Methods:Firstly,0.2 mL of precipitant and 5 mL of ultrapure water were added for mixing and standing,and then 5 mL of nitric acid was added for microwave digestion.After cooling,the volume was fixed to 35 mL with ultrapure water,and then 10 mL of ammonia,1 mL of stabilizer and 50μL of TritonX-100 were added in sequence,avoiding the iodine loss.Results:The detection limit was 0.044 mg/kg,while iodine presented favorable linearity in the range of 0~20μg/L with correlation coefficient(r)of 0.9999.The precision of the method(RSD%)was less than 5%,and the spiked recoveries of real samples is 90.2%~107.7%.The measured values of various standard substances are consistent with the labeled values.The iodine content of the same milk powder was similar to that of GB 5009.267—2020.Conclusion:The method showed the advantages of high efficiency,good recovery and accurate for the determination of iodine contents in milk powder,ensures personnel safety and reduces instrument maintenance cost.