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

Abstract

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.

Keywords

• oscillation
• leaching
• fully automatic kjeldahl analyzer
• ammonium acetate
• ammonium chloride-ammonium acetate
• soil
• cation exchange capacity