土壤中碘的灼烧浸取-砷铈催化分光光度测定方法

Determination of iodine in soil by arsenic-cerium catalytic spectrophotometry after ignition leaching

目的提出一个容易控制、设备简单的土壤中碘测定的实验方法。方法精选混合助剂(质量比碳酸钾∶硫酸锌∶氯化钠=3∶2∶1)在坩埚中分上下两层包围土壤试样,再将坩埚置于马弗炉中750℃灼烧30 min,冷却到室温后,用四甲基氢氧化铵溶液浸取碘,静置1 h。吸取上清液,用碘催化砷铈接触分光光度法测定碘含量。计算6批次标准曲线的精密度;随同土样分析全过程,做10份空白实验,计算检出限;对5种国家标准物质中的碘进行10次检测,计算准确度和精确度。结果在标准曲线的线性范围0!g/L^500!g/L内,碘浓度C与吸光度A的对数值相关系数r>0.9993,碘的检出限为9.4 ng(取样量为1 g);相对标准偏差为3.4%~8.3%,对国家标准物质检测的相对误差为2.0%"7.4%。结论本方法需用仪器简单,容易掌握推广,检出限低,精密度和准确度均能满足一般分析要求。

Objective To propose a easy - control and easy - operated test method for determination of iodine in soil. Methods Soil samples in the crucible were surrounded by preferably - mixed additives （ quality ratio of K2CO3 , ZnSO4 and NaC1 was 3 ： 2 ： 1 ） consisting of upper and lower layers. Then the crucibles were placed in a muffle furnace at 750 ℃ for 30 - min calcination. After cooling to room temperature, the iodine was leached by tetramethylammonium hydroxide solution in static for 1 h. Then the supernatant was taken to determine the content of iodine by arsenic - cerium catalytic spectrophotometry. The standard series were determined in 6 batches, and the precisions were calculated. Along with the soil sample testing, 10 copies of blank samples were detected, and the detection limits were calculated. Iodine was detected in 5 kinds of national standard materials for 10 times, and the accuracy and precision were calculated. Results The linear range of standard curve was 0 μg/L ~ 500 μg/L. The correlation coefficient （r） between iodine concentration （c） and the absorbance （A） logarithmic was greater than 0. 9993. The detection limit of iodine was 9.4 ng （ sample volume of 1 g）. The relative standard deviation was 3.4% - 8.3%. The relative error in the test of the national standard materials was 2.0% - 7.4%. Conclusion This method is simple in instrument, easy popularized, with low detection limit. Furthermore, its precision and accuracy can both meet the general analysis requirements.