元素分析仪(Elementar Vario MACRO)测定石灰性土壤C、N时存在问题的探讨

DISCUSS ON THE PROBLEM OF ELEMENTAR VARIO MACRO DETERMINING LIME SOIL C,N

壤全氮、土壤有机质的测定对农业生产和科学研究都有重要意义。因此在许多实验室里,土壤全氮、土壤有机质都被作为一项常规分析项目。土壤全氮量的测定百余年来沿用杜马氏法和凯氏定氮法。测定土壤有机质的方法主要有3种:干烧法、化学氧化法、灼烧法,1989年农业部颁布了国标GB9843-88《土壤有机质测定法》。近年来使用元素分析仪(Elementar Vario MACRO)测定土壤C、N也越来越广泛,元素分析仪是一台用于快速,定量测定元素C、H、N、S的全自动分析仪。用元素分析仪测定C、H、N的方法属于灼烧法,灼烧温度为960摄氏度,对酸性、中性土壤的测定无疑是省时准确的首选。石灰性土壤中由于碳酸盐的存在,在高温灼烧时碳酸盐分解,形成CO2,使土壤有机质的测定结果偏高。降低燃烧管温度测定(630摄氏度),由于样品用锡箔纸包裹,锡箔纸在燃烧管内燃烧生成氧化锡为放热反应,增加燃烧管内的温度高于设定温度,增加碳酸钙的分解测定值偏高,燃烧管温度设定在低于碳酸盐分解点时仪器密封不严实,使测定结果偏低。用盐酸处理土壤中碳酸盐,其后测定有机质时,因土壤中的富里酸溶于酸,使测定结果偏低。因此元素分析仪不适于石灰性土壤有机质的测定。

The measure of soil total nitrogen and soil organic matter are extremly significant for agricultural production and scientific research.So in many laboratories,analysis of soil total nitrogen and soil organic matter were as a routine analysis of project.Handreds of years,it still use the way of Dumas and Kjeldahl determination to measure the Soil total nitrogen.Determination of soil organic matter method basically has 3 ways： dry heating method,chemical oxidation and burning method.In 1989,agriculture government promulgated the encoding standard GB9843-88,＂the determination method of soil organic matter＂.Elementar Vario Macro is an automatic analysis machine which been used to measure C,H,N,S quantitative.In recent years,it is used more abroad in measuring C,N.The methods which use Elementar Vario Macro determine C,H,N belong to burn method,calcination temperature is 960 degrees,besides,it is undoubtedly the best way to measure of acid or neutral soil.Because it has some carbonate exist in lime soil,and carbonate will decomposed in high temperature burning which then formed to CO2,this process will made the result of soil organic become a little higher.Another way to measure is the reduce combustion tube temperature measurement,because the sample with the foil is packaged,foil in burning pipe burn for generating oxide tin exothermic reaction,it is an exothermic reaction when silver paper been burned in the combustion tube which also produced jewellers putty.Made the combustion tube＇s inside temperature higher than the settled temperature,and made the value of calcarea carbonica resolve measurement much higher,if the it is not exactly tight when settle of combustion tube＇s temperature is lower than carbonate＇s decomposition point,the result will lower than the truth.Using hydrochloric acid treat on soil organic matter,then measuring the organic matter,because the fulvic acid in soil is soluble in acid,the determined result were be lower.Therefore,Elementar Vario Macro is not suitable to determine of lime soil organic matter.