摘  要:研究了过硫酸钾质量及前期处理条件对水中总氮测定的影响。在常压及水浴92℃下， K2S2O8的吸光度会随着加热时间的延长而增大，其原因尚不清楚。在高压及133℃消解条件下， K2S2O8的吸光度随时间的延长而降低，反应到1个小时基本稳定。在高压及133℃消解条件下，尿素的分解率随着时间的延长增大，达到1.5h分解达到稳定。高温高压下，10g/L的尿素溶液在3.5h时的分解出现剧增，此前则变化不明显，3.5h后又保持稳定。在高压高温及133℃，过硫酸钾对尿素的氧化程度，随着加热时间的延长而增大，1.0h达到稳定态，氧化速度显著高于没有K2S2O8的情况。硝酸根标准溶液-吸光度具有良好的线性关系，线性方程如下：A=0.2317x + 0.1577, r=0.9852；总氮含量测定的前处理条件为：133℃高，在高压消解罐中，反应时间1.0h。

关键词：总氮；紫外分光光度法；过硫酸钾；分解率；高温高压

ABSTRACT:The influence of K2S2O8 quality and pre-treatment of samples on total nitrogen was studied. At ordinary pressure the absorption of alkaline K2S2O8 solution increased with time increased at 92℃ and the reason remained unclear. But the absorption decreased with time increased at high pressure , at 133℃, and it remained the constant nearly after 1.0 hour. Decompose of containing K2S2O8 urea increased clearly at short time than not containing K2S2O8. A Mutation phenomenon of decompose of Urea was observed at different time in the solution, and decompose of 10g/L of urea solution closed completely at high temperature and high pressure. Linear relationship of absorption to nitrate ion concentration was good, equation of linear regression as: A=0.2317x + 0.1577, r = 0.9852. The pretreatment conditions of containing nitrogen sample are the following: 133℃, 1.5 hours, reaction in the Digestion high-pressure tank.

Keywords:  total nitrogen, ultraviolet spectrophotometry , potassium sulfate oxidation , decomposition rate , high pressure and temperature