2种消解仪不同消解条件对凯氏定氮法测定结果的影响

Effect of Different Digestion Conditions of Two Kinds of Digestion Instruments on the Determination Results of Kjeldahl Method

为了确保不同消解仪准确测定土壤全氮,对2种消解仪的消解条件进行分析讨论。结果表明,红外消解仪适宜设定温度为370℃,石墨炉为380~400℃。氮质量分数为0.237~8.8g/kg的样品,红外消解仪的适宜消解时间为57~107min,石墨炉为60~114min;2种消解仪的适宜消解温度和消解时间存在一定差异,这与消解仪加热方式、消解管尺寸及受热面积、升温速度等密切关联。2种消解仪在适宜温度及时间条件下消解样品,检测准确稳定,所测全氮趋于一致,两者相关性良好(R^2=0.9999)。因此,不同消解仪的适宜消解条件应结合具体情况,通过一系列试验选择确定。

In order to ensure the accurate determination of soil total nitrogen by different digestion instruments,the digesting conditions suitable for infread digester instrument and graphite furnace were explored.The results showed that the suitable setting temperature was 370 ℃ for the infread digester instrument and 380-400 ℃ for the graphite furnace.In the measuring range of nitrogen mass fraction from 0.237 to 8.8 g/kg,the suitable digestion time of samples was 57 to 107 min for the infread digester instrument,and 60 to 114 min for the graphite furnace;These difference on the suitable digestion temperature and the digestion time was closely related to heating method, digestion tube size,heating area,and heating speed of the digestion instruments.The sample was digested by two digestion instruments under the suitable temperature and time conditions,and the detection results were accurate and stable.The total nitrogen measured was consistent,with high correlation between two digestion instruments ( R^2=0.999 9).Therefore,the digestion conditions suitable for different digestion instruments should be determined by a series of tests.