振荡交换-抽滤淋洗结合凯氏定氮法快速测定土壤中的阳离子交换量

Rapid Determination of Soil Cation Exchange Capacity by Automatic Kjeldahl Analyzer after Oscillating Exchange and Suction Filtration

测定土壤阳离子交换量(CEC)的行业标准方法(LY/T1243—1999)是采取离心分离结合手工蒸馏进行滴定,耗时长、操作繁琐。为了缩短反应时间,提高检测效率,本文利用乙酸铵对酸性和中性土壤进行处理,用氯化铵-乙酸铵对石灰性土壤进行处理,应用振荡和抽滤装置快速交换和清洗阳离子,通过全自动凯氏定氮仪对吸附的铵根离子进行测定,由此计算CEC值。结果表明:在最佳的振荡和蒸馏时间、滴定酸浓度、指示剂配比等实验条件下,一个批次样品(100件)的分析流程仅需要12h,比传统方法检测时间缩短近80%。经国家标准物质验证,测定结果与推荐值相符,5次测定的相对标准偏差均小于1. 5%。本方法免去了多次离心分离操作,解决了待测成分损失、CEC测定值偏低的问题,提高了检测效率和准确度,较林业标准方法的成本低,可操作性强,适用于土壤环境质量评价、地区土壤抽样调查等大批量土壤样品分析。

BACKGROUND:The industry criteria of determination of soil cation exchange capacity(CEC)(LY/T1243-1999)uses centrifugal separation combined with manual distillation and titration,which is complex and time consuming.OBJECTIVES:Determination of soil cation exchange capacity by automatic Kjeldahl analyzer after oscillating exchange and vacuum filtration.METHODS:The acidic and neutral soils were treated with ammonium acetate,the calcareous soil was treated with ammonium chloride-ammonium acetate,and the cations were quickly exchanged and cleaned by shaking and by using suction filtration equipment,and adsorbed by a fully automatic Kjeldahl analyzer.The ammonium ion was measured to calculate the CEC value.RESULTS:The experimental results show that,under the optimized oscillation and distillation,concentration of titration acid and ratio of indicator conditions,the analysis of one batch sample(100 pieces)only takes 12 hours.Compared with traditional methods,the detection time is shortened by nearly 80%.The results of national standard materials determined by the proposed method are in accordance with the certified values,the relative standard deviation is less than 1.5%(n=5).CONCLUSIONS:The method eliminates multiple centrifugation operations,solves the problem of low component loss and CEC measurement value deviations,and improves detection efficiency and accuracy.This method has a lower cost than the forestry standard method,and has high operability and is suitable for analysis of large-scale soil samples such as environmental quality assessment and regional soil sampling surveys.