提出了碱熔-超声提取-离子色谱法测定土壤中总氟化物(以F^-计)含量的方法。称取过筛后的土壤样品0.2000g于镍坩埚中,加入氢氧化钠2.00g,用马弗炉以程序升温方式(以5℃·min^-1速率升温至300℃,保持10min;再以5℃·min^-1速率升温至560℃,保持30min)熔融样品。熔融结束后,将镍坩埚放入预先装有40mL水的烧杯中,超声提取10min,将提取液转移至100mL比色管,用15mL水清洗烧杯3次,清洗液转移至比色管中,缓慢加入50%(体积分数)盐酸溶液5.0mL,再用水定容,静置15min,所得溶液经0.45μm微孔滤膜过滤,滤液经Dionex^TM InGuard^TM Ag柱处理后采用离子色谱柱法测定其中总氟化物的含量。结果显示:F^-质量浓度在5.00mg·L^-1以内与其对应的峰面积呈线性关系,检出限为25mg·kg^-1;以土壤标准物质GBW 07408、GBW 07446、GBW 07447验证方法精密度和准确度,氟化物测定值的相对标准偏差(n=6)为1.1%~2.8%,相对误差为-0.87%~2.7%;方法用于分析3个实际土壤样品,氟化物的测定值分别为309,927,636mg·kg^-1,与离子选择电极法所得测定结果基本一致。

A method for the determination of total fluoride (F^-) in soil by ion chromatography after alkali fusion and ultrasound extraction was proposed. The sieved soil sample (0.200 0 g) was placed into nickel crucible, and 2.00 g of sodium hydroxide was added. The sample was fused by muffle furnace with programmed heating (the temperature was heated at 5 ℃·min^-1 to 300 ℃, keeping for 10 min at 300 ℃, and then heated at 5 ℃·min^-1 to 560 ℃, keeping for 30 min at 560 ℃). After fusion, the nickel crucible was placed into beaker pre-loaded 40 mL of water, and ultrasonic extraction was performed for 10 min. Then the extraction solution was transferred to a 100 mL-colorimetric tube, and the beaker was washed 3 times with 15 mL of water. The cleaning solution was transferred to the above colorimetric tube, and 5.0 mL of 50% (volume fraction) hydrochloric acid solution was slowly added, and then its volume was filled with water, settling for 15 min. The obtained solution was filtered by 0.45 μm microporous filter membrane, and the filtrate was processed by Dionex^TM InGuard^TM Ag column for determination of total fluoride by ion chromatography. As shown by the results, linear relationship between the values of mass concentration and its corresponding peak area of F^- was kept within 5.00 mg·L^-1, with detection limit of 25 mg·kg^-1. The soil reference materials GBW 07408, GBW 07446 and GBW 07447 were used for verification of precision and accuracy of this method, and RSDs (n=6) of the determined values of fluoride were in the range of 1.1%-2.8%, and the relative errors ranged from -0.87% to 2.7%. This method was applied to analysis of 3 actual soil samples, and the determined values of fluoride were 309, 927, 636 mg·kg^-1, respectively, which were basically consisten with those obtained by the ion selective electrode method.