Optimization of the Method for Determining Cation Exchange Capacity in Soil by Cobalt Hexamine Trichloride Method

Compared with the traditional ammonium acetate exchange method and calcium acetate exchange method to determine CEC, cobalt hexamine trichloride method has the advantages of simple operation steps, high detection efficiency and low reagent consumption, and has obvious advantages in the analysis of large quantities of samples. The application scope of this method is limited, and the detection results of neutral and alkaline samples are good, but the detection results of acidic samples are as low as 50%.

Optimizing the test method to improve the accuracy of acidic and alkaline samples CEC, and use the method for soil available state analysis and evaluation.

Combined with previous studies, adjusted the pH to alkaline with 2mol/L sodium hydroxide solution, and the CEC measurement value of the sample was significantly improved, and the measurement results of both acidic and alkaline samples could reach the standard value range. By drawing the pH adjustment curve, the volume of 2mol/L sodium hydroxide solution was obtained in soil samples with different pH ranges, so as to adjust the pH value of unknown samples and realize the accurate determination of CEC.

The pH of the sample was adjusted on the basis of the original method. The precision of the optimized method ranged from 1.02% to 3.82% (n=6), and the accuracy met the analysis requirements.

After optimization, the application scope of the method is wider, the precision and accuracy are improved, and the detection efficiency of a large number of samples is effectively improved.