过硫酸钾氧化法测定溶液中全氮含量的影响条件研究

Effects of different conditions on the determination of total nitrogen in solution by persulfate oxidation method

研究了过硫酸钾试剂质量、氧化条件(温度和时间)及试验用水类型对过硫酸钾氧化法测定溶液全 氮含量的影响。结果表明,不同厂家生产的过硫酸钾产品氧化后,其在220和275 nm波长处的吸收峰存在极显著 差异,空白矫正吸光值(A220-2A275)高达2．5左右,严重影响测定结果的准确性;采用蒸馏水和去离子水对测定结 果无明显影响,均可满足试验要求;120-124 C高压锅氧化30 min的空白吸收值较低,并可定量回收溶液中的尿 素态氮和铵态氮,是较为适宜的氧化方式;采用0．15 mol／L NaOH和30 g／L过硫酸钾氧化剂试配,当样品和氧化 剂的加入体积比为1:1时,可氧化尿素态氮的最大范围为20 mg／L。

This study evaluated the effects of the potassium persulfate products from two different companies ,oxidizing methods （boiled water and autoclave） and the types of pure water used in the experiment on the accuracy of total nitrogen in solution determined by persulfate oxidation method. The results showed that there were significant differences in absorbance （at 220 and 275 nm） after autoclaving between the different potassium persulfate products produced by different companies; the blank absorbance of a product was as high as 2.5,and had a significant effect on the determination of the method. The types of water,i, e. ,distilled water or deionized water,had no significant effects on the N recovery of urea. Auto- claving oxidation method （30 min at 120 C） was considered to be the optimum oxidizing method,which had a lower blank absorbance,and the urea-nitrogen and ammonium-nitrogen could be recovered complete- ly. When the volume ratio of oxidizing reagent （0. 15 mol/L NaOH and 3.00 g/L K2S208） to sample was 1 ： 1, the maximum oxidation concentration of urea-nitrogen was about 20 mg/L.