凯氏法测定土壤全氮的方法改进

采用凯氏法测定土壤全氮对9种不同类型的土壤进行测定,通过实验比较不同的还原剂、氧化剂和催化剂,发现以五水合硫代硫酸钠做还原剂,以硫酸为主要氧化剂,以K2SO4＋CuSO4＋TiO2做催化剂,具有操作简便、省时、无污染的优点。该方法加标回收率82.5%～96.0%,标样测试相对误差1.4%,精密度1.9%～10.8%,检出限14mg/kg。

Method Improvement of Kjeldahl Method for Determination of Total Nitrogen in Soil

The total nitrogen in soils of 9 different types was determined by Kjeldahl method. By comparing the different reductant, antioxidants and catalyst in the environment, it proves that it is best to take the Sodium Thiosulfate Pentahydrate as reductant; the Sulfuric acid as the main antioxidant; and the CuSO4＋K2SO4＋TiO2 as catalyst. It is convenient, time saving and no pollution. The results shows that the recoveries of nitrogen are 82.5%～96.0%, the relative error of reference material of soil are 1.4%, the relative standard deviations of soils of 9 different types are between 1.9%～10.8%, and the detection limit is 14mg/kg.