影响总氮测定准确度的关键因素研究

Discussion on Key Factors Affecting Total Nitrogen Determination Accuracy

采用紫外分光光度法测定水质总氮时易出现实验空白值偏高、结果准确度偏低等情况,给分析者带来诸多困扰。根据实际工作经验,对影响总氮测定准确度的几个关键因素进行了研究探讨。结果表明,空白值偏高是影响总氮测定的主要因素,而玻璃器皿洁净度、实验用水、过硫酸钾试剂纯度及碱性过硫酸钾溶液的配制和贮存、消解时间及冷却时间等因素与空白值密切相关,均须严格控制。另外,还需注意水样的酸碱度及其它实验细节如消解时比色管是否扎紧、高压灭菌锅是否清洁、消解后溶液是否摇匀及悬浮物的干扰等,从而大大提高总氮测定的准确度。

When the total nitrogen content of water is determined by ultraviolet spectrophotometry, it tends to result in the higher experimental blank value and the lower accuracy, which causes a lot of trouble for analysts. According to the practical work experience, several key factors affecting the accuracy of total nitrogen determination were discussed in detail in this paper. The results showed that the higher blank value was the main factor affecting the determination of total nitrogen, among which the cleanliness of glassware, the experimental water, the purity of potassium persulfate and the preparation and storage of alkaline potassium persulfate solution, digestion time and cooling time were closely related to the blank value, therefore all of them should be strictly controlled. In addition, it’s necessary to pay attention to the pH of the water sample and other experimental details such as tightening the colorimetric tube during digestion, keeping the autoclave clean, shaking the colorimetric tubes after digestion and the interference of suspended matter in solution. The purpose is to greatly improve the accuracy of total nitrogen determination.