振荡抽滤-pH计指示电位滴定法快速测定土壤样品中阳离子交换总量

为了提高土壤中阳离子交换量(CEC)分析效率及分析准确度,采用乙酸铵或氯化铵-乙酸铵溶液对土壤样品进行处理,并采用振荡交换、抽滤分离的方式进行离子交换、铵离子清洗。土壤饱和吸附的铵离子用甲醛-CaCl2溶液交换后,采用氢氧化钠溶液滴定,并用pH计准确指示滴定终点,由此测定CEC含量。选用5个国家一级有效态标准物质进行验证,测定值与推荐值相符,相对标准偏差均小于7%,提高了CEC的分析效率与准确度,更加适用于大批量样品的测定。

Rapid Determination of Total Cation Exchange in Soil Samples by Oscillating Suction Filtration-pH Meter Potentiometric Titration

In order to improve the efficiency and accuracy of cation exchange capacity (CEC) analysis in soil, this article uses ammonium acetate or ammonium chloride-ammonium acetate solution to treat soil samples, and then ion exchange and ammonium are carried out by shaking exchange and suction filtration separation. Ion cleaning. After the saturated ammonium ions in the soil were exchanged with formaldehyde-CaCl2 solution, it was titrated with sodium hydroxide solution, and the end point of the titration was accurately indicated with a pH meter, thereby determining the CEC content. Five national first-level effective reference materials were selected for verification. The measured values were in accordance with the recommended values, and the relative deviations were all less than 4%. This method improves the analysis efficiency and accuracy of CEC, and is more suitable for the analysis of large quantities of samples.