杜马斯燃烧法和凯氏定氮法在土壤全氮检测中的比较研究

Comparison of Dumas combustion and Kjeldahl methods for determining total nitrogen content in soil

选用6组不同全氮含量的土壤样品(梯度为0%~0.06%、0.06%~0.1%、0.1%~0.2%、0.2%~0.3%、0.3%~0.4%和0.4%~0.5%)和4份土壤有效态成分分析标准物质为试验材料,分别采用杜马斯燃烧法和凯氏定氮法测定其全氮含量,并对两种方法测定结果的精密度、准确度和相关性及检测成本进行了比较分析。对土壤有效态成分分析标准物质全氮含量的检测,两种方法测定结果都接近于真实值,比较两种方法的相对标准偏差(RSD)和相对误差(RE)值,可确定杜马斯燃烧法精密度更高,且准确度更好;对于含氮量范围为0%~0.06%的样品,两种方法的测定值之比(D/K)为0.692~0.965,杜马斯燃烧法测定结果的变异系数为0.00%~9.96%,测定结果不稳定,两种方法的测定值间存在显著的线性相关,但R2仅为0.904 9;而含氮量大于0.06%的样品,两种方法的测定值之比(D/K)为0.940~1.104,变异系数均小于5%,测定结果间存在显著的线性相关(R2=0.997 9)。在检测成本方面,完成相同数量样品检测,杜马斯燃烧法所需时间和人力都约是凯氏定氮法的1/2。因而,杜马斯燃烧法是一种环保、高效的土壤全氮检测方法,对于含氮量范围为0%~0.06%的土壤样品,凯氏定氮法的测定结果更接近于真实值,而对于含氮量大于0.06%的土壤样品,杜马斯燃烧法更加适用。

In order to compare and analyze the precision,accuracy,correlation and testing cost of Dumas combustion and Kjeldahl methods for determining total nitrogen(TN)content in soil,this study was conducted to examine the determination of TN contents in 6 groups of soil samples with different TN content(0%~0.06%,0.06%~0.1%,0.1%~0.2%,0.2%~0.3%,0.3%~0.4%and 0.4%~0.5%)and 4 national standard substances using Dumas combustion and Kjeldahl methods,respectively.The result showed that RSD and RE of Dumas combustion method for determination of TN content in 4 national standard substances were lower than those of Kjeldahl method,which indicated Dumas combustion method was better.For samples with nitrogen content ranging from 0%to 0.06%,the range of coefficient of variation(CV)was 0.00%~9.96%with Dumas combustion method and the ratio of Dumas combustion and Kjeldahl methods(D/K)was 0.692~0.965.Good linear correlations(R2=0.9049)were obtained between the two different methods.For samples with nitrogen content greater than 0.06%,the ratio of D/K was 0.940~1.104 and the range of coefficient of variation(CV)were less than 5%with Dumas combustion and Kjeldahl methods.Good linear correlations(R2=0.9979)were obtained between the two different methods.The time and manpower required by Dumas combustion method is about 1/2 of that of Kjeldahl method for the same number of samples.Therefore,Dumas combustion method is an environmentally friendly and efficient method for TN determination in soil.For samples with nitrogen content ranging from 0%to 0.06%,the result was closer to the real value with Kjeldahl method.For samples with nitrogen content greater than 0.06%,Dumas combustion method was more applicable.