Pacquette Lawrence H, Levenson Alan M, Thompson Joseph J
Abbott Nutrition, Global Research Services, 3300 Stelzer Rd, Columbus, OH 43219, USA.
J AOAC Int. 2012 Jan-Feb;95(1):169-76. doi: 10.5740/jaoacint.10-472.
A single-laboratory validation by inductively coupled plasma-mass spectrometry was developed for the determination total iodine (m/z 127) in infant formula and adult nutritional products. All samples were digested in nitric acid using a closed vessel microwave oven system; Te (m/z 130) was used as an internal standard. To prevent loss of iodine, ammonium hydroxide solution was added to the samples immediately after digestion. The method quantitation limit for total iodine was 0.3 ng/mL, but a practical LOQ was used at 1.0 ng/mL, a concentration at which there was a negligible bias due to nonlinearity. The total iodine concentrations (112-1900 ng/g) in 14 out of 15 nutritional products were within specification limits. Within-day and day-to-day (6 independent days) precision values were < 10% RSD. The observed precision for the overall mean (18 independent days) of a control sample was approximately 4% RSD. In two National Institute of Standards and Technology standard reference materials, total iodine results were within certified limits. Sample spike recoveries for all 15 nutritional products were 92-105%. The data show that a conventional microwave oven digestion procedure can be used to prepare samples for iodine determination. Therefore, this technique is very compatible with other methods being proposed as modern official methods for the analysis of minerals in nutritional products.
建立了一种通过电感耦合等离子体质谱法进行的单实验室验证方法，用于测定婴儿配方奶粉和成人营养产品中的总碘（m/z 127）。所有样品均使用密闭容器微波炉系统在硝酸中进行消解；碲（m/z 130）用作内标。为防止碘损失，消解后立即向样品中加入氢氧化铵溶液。总碘的方法定量限为0.3 ng/mL，但实际定量限采用1.0 ng/mL，该浓度下由于非线性导致的偏差可忽略不计。15种营养产品中有14种的总碘浓度（112 - 1900 ng/g）在规格限度内。日内和日间（6个独立日期）精密度值的相对标准偏差（RSD）< 10%。对照样品总体均值（18个独立日期）的观察精密度约为4% RSD。在两种美国国家标准与技术研究院标准参考物质中，总碘结果在认证限度内。所有15种营养产品的样品加标回收率为92 - 105%。数据表明，传统的微波炉消解程序可用于制备用于碘测定的样品。因此，该技术与作为营养产品矿物质分析现代官方方法所提出的其他方法非常兼容。
