高碘尿样的低砷量砷铈催化分光光度测定方法

目的 建立高碘尿样的低砷用量砷铈催化分光光度测定方法。方法 取0.20 ml尿样按现行尿碘测定标准方法(WS/T 107-2006)进行样品消化处理，并将现行标准法检测每份样品的亚砷酸溶液用量由0.100 mol/L(含氯化钠25 g/L)2.5 ml改变为0.025 tmol/L(含氯化钠40 g/L)2.5 ml，硫酸铈铵溶液用量由0.076 mol/L 0.30 ml改变为0.025 mol/L 0.50 ml,吸光度(A)测定波长由420 nm改为380 nm，检验新方法的标准曲线线性关系及线性范围，样品测定精密度、准确度，与现行标准法比较尿碘测定结果，并检验此新方法在20～30℃范围内砷铈反应温度与反应时间的适宜组合。结果 新方法砷铈反应在20 ～ 30℃范围内任一稳定温度及固定反应时间都有碘质量浓度(C)与测定A值定量关系，回归方程式为C=a+ blgA，标准曲线线性尿碘范围为300～1200μg/L(r=- 0.9999)；尿碘为330.3、517.3、712.6、1042.3μg/L时，新方法测定相对标准偏差(RSD)分别为1.0％ (3.2/330.3)、0.4％ (2.0/517.3)、0.5％ (3.9/712.6)、0.9％(9.4/1042.3)；新方法测定300～1200 μg/L范围内低、中、高含碘量不同的4份尿样，加碘标平均回收率分别为99.1％(148.6/150.0)、97.5％(195.0/200.0)、98.8％( 395.3/400.0)、98.2％( 392.7/400.0)，回收率范围为93.4％ (186.8/200.0)～101.5％(202.9/200.0)，总平均回收率为98.3％；分别在不同反应温度下用新方法测定4种高尿碘标准物质，测定结果均在给定值的不确定度范围内，且相对偏差均＜2％；用新方法与现行标准法分别测定16份高碘尿样，检测结果比较差异无统计学意义(|t|=0.727,P＞0.05)。新方法反应温度与时间适宜组合系列数据为20℃和33 min、25℃和25min、30℃和19 min等。结论 新方法可直接取高碘尿样进行检测，避免了现行标准方法中测定高碘尿样需多倍稀释的稀释误差和操作不便，且大大减少了含砷废液量，减少了环境污染和节省了试剂，操作简便易行，精密度与准确度较好，适合推广应用。

Method with low usage amount of arsenic trioxide for measuring high concentration iodine in urine by As3+-Ce4+ catalytic spectrophotometry using ammonium persulfate digestion

Objective To establish a new method with low usage amount of arsenic trioxide for measuring 300 - 1200 μg/L high concentration iodine in urine by As3+-Ce4+ catalytic spectrophotometry using ammonium persulfate digestion, which would be convenient for monitoring urinary iodine in excessive iodine regions and to reduce environmental arsenic pollution. Methods Calibrators and urine samples(0.20 ml each) were digested according to the current standard detection method of urinary iodine(WS/T 107-2006). At the same time, improving the current standard method, the amount of arsenious acid solution was reduced from 0.100 moL/L H3AsO3 (containing NaCl 25 g/L) 2.5 ml to 0.025 mol/L H3AsO3(containing NaCl 40 g/L) 2.5 ml; amount of ceric ammonium sulfate solution was reduced from 0.076 mol/L 0.30 ml to 0.025 mol/L 0.50 ml; and photometric wavelength was changed from 420 nm to 380 nm. The new method was evaluated by standard curve linearity and linear range, sample detection precision, accuracy, and the results of urinary iodine were compared with those determined bycurrent standard method, and this new method was also tested of suitable combination of reaction temperature and reaction time of cerium arsenic in the temperature range of 20 - 30 ℃. Results The calibration relation of C =a + blgA (C: iodine concentration, A : measuring absorhance) in the new method existed when As3+- Ce4+ catalytic reaction was kept at a certain stable temperature range between 20 - 30 ℃ and in certain fixed reacting time. The linear range of the calibration curve was 300 - 1200 μg/L and the linear correlative coefficient was- 0.9999. The relative standard deviations(RSD) were 1.0％(3.2/330.3), 0.4％(2.0/517.3), 0.5％(3.9/712.6) and 0.9％(9.4/1042.3) when measuring urine samples with iodine concentration of 330.3, 517.3,712.6, and 1042.3 μg/L, respectively. The total average recovery was 98.3％ with a range of 93.4％ (186.8/200.0) - 101.5％ (202.9/200.0) when measuring 4 urine samples containing different concentration of high iodine, and average recovery was 99.1％ (148.6/150.0), 97.5％ (195.0/200.0), 98.8％ (395.3/400.0), and 98.2％ (392.7/400.0),respectively. The test results of four urinary iodine standard materials were all within the given value range and the relative deviations(RD) were all ＜ 2.0％ at different test temperature, respectively. No significant difference was found between the results of the 16 urine samples containing high concentration of iodine determined by the new method and the current standard method (|t| =0.727, P ＞ 0.05). The table of suitable combination of As3+-Ce4+ reaction temperature and reaction time for this method was obtained(such as 20 ℃ and 33 min, 25 ℃ and 25 min,30 ℃ and 19 min, etc). Conclusions This method greatly reduces the amount of arsenic in waste, reduces pollution, saves reagents, and this method is easier to be performed with better precision and accuracy, which is suitable for measuring high concentration of iodine in urine.