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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 an experimental method for the determination of iodine in soils with easy control and simple equipment. Method Selection of mixing aids (mass ratio of potassium carbonate: zinc sulfate: sodium chloride = 3: 2: 1) in the crucible in the upper and lower layers surrounded by soil samples, and then the crucible placed in a muffle furnace 750 ℃ burning 30 min, cooled to room temperature, the leaching of iodine with tetramethylammonium hydroxide solution, allowed to stand for 1 h. The supernatant was aspirated, and the iodine content was determined by iodine-catalyzed arsenic-cerium contact spectrophotometry. Calculate the precision of six batches of standard curve; with the entire soil sample analysis process, do 10 blank experiments, calculate the detection limit; the iodine in the five kinds of national standards were tested 10 times to calculate the accuracy and accuracy. Results In the linear range of the standard curve, the correlation coefficient r of iodine concentration C and absorbance A was 0.9993 and the detection limit of iodine was 9.4 ng (sampling volume was 1 g) in the range of 0 g / L to 500 g / L. ; The relative standard deviation was 3.4% ~ 8.3%, and the relative error of the detection of national standard substance was 2.0% ”7.4% .Conclusion The method requires simple instrument, easy to popularize, low detection limit, precision and accuracy To meet the general analysis requirements.