应用高频红外碳硫仪测定农用地土壤样品中有机质含量

应用高频红外碳硫仪测定农用地土壤样品中的有机质，避免了传统方法中的试样液体转化环节，测定效率高，但存在土壤样品电磁感应低和基体影响较大等问题。本文通过实验优化了样品称样量、助熔剂铁和钨的添加量等测定条件，结果表明：当样品称样量为0.05g、助熔剂铁添加量为0.40g、钨添加量为1.50g时，有机质测定效果最佳。通过土壤标准物质进行验证，方法检出限为0.003%，相对标准偏差（RSD，n=7）小于4%，测定值与认定值的相对误差小于5%，且不同分析人员的测定结果间没有显著差异。采用本法与重铬酸钾容量法对甘肃省农用地土壤样品进行测定，两种方法测定值的绝对误差为-0.25%~0.28%，测定结果之间呈极显著线性正相关（R²=0.9736），表明两种方法的一致性很好。本方法的检出限、精密度、准确度均满足农用地土壤样品有机质测定要求。

Determination of Organic Matter Content in Farm Land Soil by High Frequency Infrared Carbon-Sulfur Analyzer

BACKGROUND: The application of high frequency infrared carbon-sulfur analyzer to determine the organic matter in agricultural soil samples avoids the traditional method of sample liquid conversion. The method has a high measurement efficiency, but has problems such as low electromagnetic induction of soil samples and greater influence of the matrix.
OBJECTIVES: To solve the problems of low electromagnetic induction and large matrix effect in the determination of organic matter in agricultural soil samples.
METHODS: The iron and tungsten flux was optimized for the sample size. An accurate and efficient method for the determination of soil organic matter content was established by high frequency infrared carbon-sulfur analyzer.
RESULTS: When the conditions set for a sample size of 0.05g, the flux iron content was 0.40g, and the tungsten content was 1.50g, optimum results of organic content were obtained. The method was verified by soil standard materials. The detection limit of this method was 0.003%, the relative standard deviation (RSD, n=7) was less than 4%, and the error between the analytical result and the standard value was less than 5%. There was no significant difference between the results of different analytical staff. The proposed method and potassium dichromate volumetric method were used to analyze soil samples in farm land of Gansu Province. The absolute error ranges of this method and potassium dichromate volumetric method were from -0.25% to 0.28%. The positively linear correlation between the determination results (R²=0.9736) indicated that the two methods were in good agreement.
CONCLUSIONS: The detection limit, precision and accuracy of the established method meet the requirements of the soil samples of farm land.