分光光度法测定土壤有机质的含量

Spectrophotometric determination of organic matter in soil

建立了以K2Cr2O7测定土壤中有机质的分光光度法。在硫酸溶液中,以Ag2SO4为催化剂,加入过量K2Cr2O7标准溶液氧化葡萄糖中的有机碳,铬(Ⅵ)可用有机碳还原至铬(Ⅲ),其最大吸收波长为585 nm。有机碳浓度在1.60～68.00 mg/L范围内与溶液吸光度呈良好线性关系,线性回归方程为A=0.409ρ-0.067 93(mg/L),相关系数r=0.999 5,检出限为0.190 mg/L,相对标准偏差(RSD)为0.7%,表观摩尔吸光系数ε=4.91×103L/(mol.cm)。测定国家标准土壤样品中有机质的含量,相对误差小于4.3%。

A spectrophotometric method has been established to determine soil organic matter using potassium dichromate.In sulfuric acid solution,organic carbon of glucose was oxidized by over-amounts potassium dichromate with silver sulfate as a catalyst,Cr（Ⅵ） was reduced to Cr（Ⅲ） by organic carbon,the maximum absorption wavelength was 585 nm.A good linear relationship was obtained in the range of 1.60～68.00 mg/L of organic carbon.The linear regression equation was A=0.409ρ-0.067 93（mg/L） with a correlation coefficient of 0.999 5 and the apparent molar absorption coefficient of 4.91×103 L/（mol·cm）.The detection limit was 0.190 mg/L,while RSD was 0.7%.The relative error of the mentioned method was less than 4.3%.