流动分析仪同时测定土壤和植物全氮含量方法的改进

Optimization of Determination Method of Total Nitrogen Content in Soil and Plant by Flow Analyzer at the Same Time

【目的】改进流动分析仪同时测定土壤和植物样品全氮含量的检测方法,为准确快速测定土壤和植物样品全氮含量提供参考依据。【方法】设置凯式消煮法的硫酸加入量为3.0、4.0和5.0 mL,使用流动分析仪分别测定各土壤和植物样品硫酸消煮液的全氮含量,分析不同硫酸加入量对其全氮含量测定结果的影响,并分析流动分析仪法与传统方法(扩散法)测定全氮含量的相关性。【结果】凯式消煮法的硫酸加入量可优选为3.0 mL,消解硫酸量(mL)与缓冲液中氢氧化钠浓度(g/L)适宜比值在0.158~0.163。在流动分析仪同时测定土壤和植物样品全氮含量的回收试验中,平均回收率为96.40%~102.07%,相对标准偏差(RSD)为0.34%~1.52%;在重复性试验中,全氮含量的变异系数(c.v.)小于3.00%。流动分析仪法与扩散法所测全氮含量无显著差异(P>0.05),两种方法所测全氮含量的回归直线y=1.0747x-0.7762,R=0.9957,二者呈显著线性相关(P<0.05)。【结论】以凯式消煮法优选硫酸量3.0 mL进行土壤和植物样品消煮,建立以其消煮液测定全氮含量的检测方法,可确保流动分析仪准确地同时测定土壤和植物样品全氮含量。

【Objective】In order to accurately and efficiently determine total nitrogen content in soil and plant,the determination method of to-tal nitrogen content in soil and plant by flow analyzer was optimized.【Method】3.0,4.0 and 5.0 mL sulfuric acid were added in Kjedahl method,and content of total nitrogen in soil and plants digestion solution were determined by flow analyzer.The influence of sulfuric acid content on the determination of total nitrogen content was discussed.The effects of different sulfuric acid amounts on total nitrogen content were analyzed,and the correlation between flow analyzer and traditional method determinating total nitrogen content was also studied.【Re-sult】The optimum amount of sulfuric acid added to the Kjeldahl digestion method was 3.0 mL,and the appropriate ratio of the amount of sul-furic acid to the amount of sodium hydroxide in the buffer solution was 0.158-0.163.The average recovery rate was 96.40%-102.07%,relative standard deviation(RSD)was 0.34%-1.52%and c.v.was less than 3.00%in the repeatability test.There was no signifi-cant difference between the total nitrogen content measured by flow analyzer method and diffusion method(P>0.05).The regression line of the total nitrogen content measured by the two methods was y=1.0747x-0.7762,R=0.9957.There was a significant linear correlation be-tween the two methods(P<0.05).【Conclusion】The optimal sulfuric acid in Kjeldahl digestion method on soil and plant is 3.0 mL.Method for the determination of total nitrogen content in digestion solution with different acidity was established so as to ensure the total nitrogen con-tent in soil and plants were determinated by flow analyzer at the same time.