高锰酸根褪色光度法测定土壤中的有机碳

建立了以KMnO。测定土壤中有机碳的分光光度法。在硫酸介质中，有机碳能快速、定量的还原高锰酸根，在加入有机碳前后，高锰酸钾溶液在波长525nm处的吸光度发生明显变化，且吸光度之差△A与加入的有机碳的浓度成正比。结果表明，有机碳浓度在0．40—28．00mg／L范围内与溶液吸光度差值呈良好线性关系，线性回归方程为△A=0．0466p＋0．058（mg／L），相关系数r=0．9987，检出限为0．170mg／a，相对标准偏差（RSD）为0．390％，表观摩尔吸光系数ε=8．39X10^3L／（mol·em）。用于测定国家标准土壤样品中有机碳的含量，相对标准偏差小于2．90％。

Determination of organic carbon in soil by permanganate fading spectrophotometry

A spectrophotometric method has been established to determine soil organic carbon using potas- sium permanganate. In sulfuric acid medium, permanganate can be reduced by organic carbon very quick- ly, the absorbance of potassium permanganate solution at 525 nm would change significantly when organic carbon presents in the solution, and the difference of absorbances in direct proportion to organic carbon concentration. The results showed that a good linear relationship is obtained in the range of 0.40 - 28.00 mg/L of organic carbon, the linear regression equation is A = 0. 046 6 p ＋ 0. 058 （rag/L） with a correlation coefficient of 0. 998 7 and the apparent molar absorption coefficient of 8. 39 ×103 L/（mol·cm）. The detection limit is 0. 170 mg/L, the RSD is 0.390%. The method has been used in the determination of organic carbon in soil standard materials, the relative standard deviation was less than 2.90%.