在酚二磺酸光度法测定水中总氮量的方法中,用高压反应釜代替比色管,改进了样品的碱性过硫酸钾消解效果,避免了样品消解不彻底,氧化剂分解不完全及样品中铵氮以氨气形式逸出等.标准曲线的线性范围在0.02~1.90 mg·L-1之间,检出限(3σ)为0.02 mg·L-1.按此方法测定了6种水样中的总氮量,测定值的相对标准偏差(n=6)均小于3.5%.用标准加入法对方法的回收率作了试验,测得结果在98%~102%之间.

In the photometric determination of total nitrogen in water with phenol disulfonic acid as color reagent,a modification of the sample digestion with alkaline potassium persulfate was made by carrying out the digestion in a pressurized reaction kettle instead of in a colorimetric tube,to avoid incomplete sample digestion,incomplete decomposition of the oxidant and loss of ammonia by evolution.Linear relationship was kept between values of absorbance and concentration of total nitrogen in the range of 0.02-1.90 mg·L-1.Detection limit (3σ) of the method found was 0.02 mg·L-1.Six water samples were analyzed by the proposed method,values of RSD′s (n=6) found were less than 3.5%.Test for recovery was made by standard addition method,giving results in the range of 98%-102%.