氨水密闭熔融—离子色谱法测定土壤和沉积物中碘的含量

Determination of Iodine in Soil and Sediment by Ion Chromatography after Closed Melting with Aqueous Ammonia

土壤和沉积物样品经采集、风干、破碎、过筛后,分取0.1000 g样品于防腐熔样罐内,加入10%(体积分数)氨水溶液(熔剂)8 mL,密闭后于190℃加热熔融12 h。加入15 g·L^(-1)抗坏血酸溶液0.1 mL,用水稀释至15 mL,离心5 min,分取10 mL上清液,过0.22μm滤膜,滤液注入离子色谱仪,在Metrosep A Supp 5-150/4.0阴离子色谱柱上用3.2 mmol·L^(-1)碳酸钠-1.0 mmol·L^(-1)碳酸氢钠混合溶液淋洗,以安培检测器检测。结果显示:碘的质量浓度在50μg·L^(-1)以内与其对应的峰面积呈线性关系,检出限(3.143s)为0.15μg·g^(-1);对标准物质和实际样品进行精密度和准确度试验,碘的测定值在认定值的不确定度范围内,回收率为95.0%~96.0%,测定值的相对标准偏差(RSD,n=6)小于10%。将上述方法和行业标准方法DZ/T 0279.23-2016进行比对,两种方法的测定值基本一致,上述方法测定值的RSD(n=6)低于行业标准方法的。

After the soil and sediment samples were collected, dried, crushed and screened, 0.100 0 g of the samples were taken and placed into an anti-corrosion melting tank, and 8 mL of 10%(volume fraction) aqueous ammonia solution(flux) was added. Under closed conditions, the mixture was heated and melted at 190 ℃ for 12 h. After 0.1 mL of 15 g·L-1ascorbic acid solution was added, the mixture was diluted to 15 mL with water, and centrifuged for 5 min. An aliquot(10 mL) of the supernatant was taken and filtered through a 0.22 μm filter membrane, and the filtrate was injected into the ion chromatograph. The mixture of 3.2 mmol·L-1sodium carbonate solution and 1.0 mmol·L-1sodium bicarbonate solution was used for eluting on the Metrosep A Supp 5-150/4.0 anion chromatographic column, and amperometric detector was used for detection. As found by results that the mass concentrations of iodine were linearly related with corresponding peak areas within 50 μg·L-1, with detection limit(3.143s) of 0.15 μg·g-1. Tests for precision and accuracy were carried out on standard substances and actual samples, and the determined values were within the uncertainty ranges of the certified values, with the recoveries in the range of 95.0%-96.0% and RSDs(n=6) of the determined values less than 10%. The above method was compared with the industrial standard method of DZ/T 0279.23-2016, giving the determined values of the two methods basically the same, and RSDs(n=6) of the determined values of the above method were lower than those given by the industrial standard method.