碱性过硫酸钾-紫外分光光度法测定水质总氮方法的改进  

Improvement of the Method for Determining Total Nitrogen in Water Quality Using Alkaline Potassium Persulfate Ultraviolet Spectrophotometry

作　　者：刘振超 李志雄 陆迁树 王晓娜 张松 胡耀华 LIU Zhenchao;LI Zhixiong;LU Qianshu;WANG Xiaona;ZHANG Song;HU Yaohua(Kunming General Survey of Natural Resources Center,China Geological Survey,Kunming 650111,China)

机构地区：[1]中国地质调查局昆明自然资源综合调查中心,云南昆明650111

出　　处：《岩矿测试》2024年第1期114-123,共10页Rock and Mineral Analysis

基　　金：中国地质调查局地质调查项目(DD20220879);自然资源部三江成矿作用及资源勘查利用重点实验室开放基金课题(SJSYS202302)。

摘　　要：水质总氮是指示水体富营养化的重要标志物,因此,开发测定水体中总氮的准确方法,对研究水体中的污染物来源、污染程度及总氮的地球化学循环过程具有重要意义。测定水质样品中的总氮,通常采用碱性过硫酸钾-紫外分光光度法,但该法对空白吸光度有严苛的要求,空白吸光度一旦超过0.030,就有可能导致测定结果严重偏低,其中,过硫酸钾的纯度和存放时间可能对测定结果影响最大;同时,采用比色管捆绑方式高温高压消解水质样品,导热较慢,消解时间偏长,捆绑时一旦比色管上的标签或记号脱落,容易导致样品混乱;样品保存条件不当也很容易造成测定结果偏低。为提高水质样品中总氮测定结果的准确性和效率,本文通过对国内外不同厂家生产的过硫酸钾进行总氮空白吸光度和存放时间对比实验,然后对两种消解方法进行消解时间对比实验,最后,对比了两种不同水质样品保存方法对测定结果的影响。对比实验结果表明:国产优级纯碱性过硫酸钾存放时间在30天内,其水质总氮空白吸光度均小于0.030;在124℃条件下,使用插置法消解样品,只用20min就能使样品消解完全;对酸化后的水质样品,其保质期从1天延长至7天。研究认为,选用国产优级纯过硫酸钾和改良过的插置法消解水质样品,与捆绑法相比,其水质总氮检出限更低,消解效率更高,且不容易出现互相污染和样品错位等情况,提高了水质总氮测定的准确度。Alkaline potassium persulfate(K_(2)S_(2)O_(8))ultraviolet(UV)spectrophotometry is the routine method to analyze total nitrogen(TN)in water and is important for studying pollutants in water and the geochemical cycling of TN.However,several analytical conditions can influence the accuracy of the results.(1)The blank,purity,and storage time of K_(2)S_(2)O_(8).For example,a blank UV of K2S2O8 exceeding 0.030 can lead to a significant underestimation of results.(2)The digestion method of bundling colorimetric tubes in high temperature and high pressure is time-consuming.(3)Improper sample storage conditions can lower measurement results.To improve the accuracy and efficiency of TN measurement in water samples,this study compared the storage times of different K_(2)S_(2)O_(8),different digestion methods,and sample storage methods.The results show that the domestic premium-grade alkaline K_(2)S_(2)O_(8) should be stored for<30 days(blank UV<0.03).The insertion digestion method is much more efficient(124°C,20min).Acidification extends samples’shelf life from 1 day to 7 days.Therefore,choosing domestic premium-grade K_(2)S_(2)O_(8) and using the modified insertion method for sample digestion results in lower detection limits,higher digestion efficiency,minimal risk of contamination and misplacement,and improved accuracy of TN measurement in water quality analysis.

关 键 词：过硫酸钾 紫外分光光度法 水质总氮 方法改进 

分 类 号：O657.31[理学—分析化学]