甲醛对Nessler法和次氯酸酚盐法测定养殖水体总氨氮的影响

水体中含一定浓度的甲醛 ,用 Nessler法测得的总氨氮 (TAN)浓度远远高于实际浓度 ,差异百分数最高达 4 5 0 .0 6 % ;用次氯酸酚盐法测得的总氨氮 (TAN)浓度则明显低于实际浓度 ,差异百分数最高可达 84 .77%。甲醛浓度范围为 10～ 4 0 mg/ L、TAN浓度为 1～ 10 mg/ L,通过双因素有重复观察值的交叉实验 ,得到如下矫正式 :(1)用 Nessler法测 TAN时 ,Y=4 .0 5 2 9- 0 .0 72 4 x1+ 0 .2 0 6 4x2 ,标准误差为 1.3381;(2 )用次氯酸酚盐法测 TAN时 ,Y=0 .1196 + 0 .0 345 x1+ 1.0 0 2 2 x2 ,标准误差为 0 .4 6 2 7。 Y为 TAN实际浓度 (mg/ L) ,x1为甲醛浓度 (mg/ L) ,x2 为测得的 TAN浓度(mg/ L )。比较含氨氮水体与不含氨氮水体中的甲醛浓度 ,方差分析结果表明 ,没有显著差异。

Effects of Formaldehyde on Measurement of Total Ammonia Nitrogen Concentration by Nessler and Salicylate Methods

The Nessler method was found to give an intense yellow color and erroneously high ammonia values in the presence of formaldehyde, the biggest difference amounted to 450.06%. The salicylate measurement also failed to detect TAN correctly in the presence of formaldehyde, giving less TAN values. The biggest difference amounted to 84.77%. The results of multiple regression showed that if the concentrations of formaldehyde lay between 10~40mg/L, and TAN concenrations lay between 1~10 mg/L, the regression equations were Y =4.052 9-0.072 4 x 1+0.206 4x 2, Y=0.119 6+ 0.034 5x 1 +1.002 2x 2(x 1 being the concentration of formaldehyde, x 2 the value of TAN measured and Y the true concentration of TAN) respectively when using the Nessler method and the salicylated method. Our experiment showed that formaldehyde did not react with ammonia in aquaculture water.