尿中碘的过硫酸铵消化-低砷量砷铈催化分光光度测定方法的验证

Verification of a method with low usage amount of arsenic trioxide for determining urinary iodine by As （Ⅲ）- Ce4＋ catalytic spectrophotometry using ammonium persulfate digestion

目的对《尿中碘的砷铈催化分光光度测定方法》（WS／T107—2006）的修订方法（以下简称修订法）进行验证。方法采集山西省地方病防治研究所职工家中儿童随意尿样1次．尿样按照尿碘含量进行分类．用于方法学指标的验证。制备碘含量为0～300、300—1200μg／L的碘标准曲线，对修订方法中标准曲线的线性关系、检出限，样品精密度、加标回收率及准确度进行验证，评价验证结果；用修订法和修订前方法（以下简称标准法）同时检测尿样，对结果进行比较分析。结果碘含量为0～300、300～1200ng／L的标准曲线，线性相关系数范围分别为-1．0000～-0．9998、-0．9999～-0．9997；最低检出限分别为1．2、303．8μg／L；测定尿碘含量分别为85．0、133．8、250．8μg／L和422．2、666．4、1073．9μg／L的尿样时，相对标准偏差分别为1．8％、1．6％、1．7％和0．9％、1．2％、0．9％；测定尿碘含量分别为79．0、111．8、174．9μg／L和312．4、472．2、637．7μg／L的尿样时，平均加标回收率分别为100．7％、101．9％、98．8％和100．1％、98．0％、100．5％，回收率范围分别为96．9％～102．8％、94．3％～103．2％；测定国家尿碘标准物质（GBW09108i、GBW091101、GBW09111a、GBW09112a），相对偏差分别为-1．0％、0．7％、0．1％、-0．4％，测定结果均在给定值的不确定度范围内。修订法和标准法同时测定了20份尿样，两种方法比较差异无统计学意义（P〉0．05）。结论修订法标准曲线有很好的线性关系，测定精密度好、重现性好、准确度高。此方法可直接取高碘尿样进行消化测定，减少了样品受污染的机会和稀释尿样带来的测定误差，更能满足尿碘测定方法特性指标的要求。

Objective To verify the feasibility and application of an improved method for determination of urinary iodine by As（m）-Ce4＋ catalytic spectrophotometry （WS/T 107-2006）. Methods Random urine samples were collected from the children of employee at Institute for Endemic Disease Prevention and Control of Shanxi. Those samples were categorized by the iodine levels and used for verification of the method. Iodine calibration curve of 0 - 300 μg/L and 300 - 1 200 μg/L iodine levels were prepared and used. The linearity and its range in the improved standard curve, sample detection limit, precision, sample standard addition recovery rate and accuracy were validated and evaluated. The improved and standard methods were both used to test the urine samples and results were compared and analyzed. Results In the iodine levels of 0 - 300 μg/L and 300 - 1 200 μg/L calibration curves, the ranges of correlation coefficient were - 1.000 0 - - 0.999 8 and - 0.999 9 - - 0.999 7, respectively. The lowest detection limits for iodine were 1.2 and 303.8μg/L, respectively. In the two ranges, when the measuring urinary iodine levels were 85.0, 133.8, 250.8 and 422.2, 666.4, 1 073.9 μg/L, the relative standard deviations were 1.8%, 1.6%, 1.7% and 0.9%, 1.2%, 0.9%, respectively. When the measuring urinary iodine levels were 79.0, 111.8, 174.9 and 312.4, 472.2, 637.7 μg/L, the average addition recovery rates were 100.7%, 101.9%, 98.8% and 100.1%, 98.0%, 100.5%, respectively. The ranges of recovery rate were 96.9% - 102.8% and 94.3% - 103.2%, respectively. In the measuring of the given urinary iodine national standard materials GBW09108j, GBW091101, GBW09111a, and GBW09112a, the relative deviations were - 1.0%, 0.7%, 0.1% and - 0.4%, respectively, the results were all within the given value range. There was no statistical difference between the improved method and the standard method in the results of 20 urine samples （P 〉 0.05）. Conclusions The improved method has great linearity, precision, repeatability and accuracy. This method can directly take urine samples with high level iodine to digest and test. It greatly reduces the chance of sample contamination and system error in diluting urine samples. It will better meet the requirements of characteristic index for measuring urinary iodine.