在应用紫外分光光度法测定水样中硝酸根离子(即Cawse法)时,发现采用200 nm作为测定波长,与原方法中用210 nm相比较,不仅提高了方法的灵敏度和准确度,而且改善了选择性.据此,作为对Cawse法的一点改进,选择200 nm作为测定波长.在此条件下,求得方法的线性回归方程为y=0.006 6+0.715 5 x(r=0.999 8),由此可得其线性范围为0.05~3.00 mg·L-1,其摩尔吸光率为1.02×104L·mol-1·cm-1.在测定不同的水样中硝酸根含量时允许小于1.0 mg·L-1亚硝酸根和小于200 mg·L-1氯离子共存.

In the application of UV-spectrophotometry to the determination of NO-3 in water (i.e.,the cawse method),it was found that better sensitivity and accuracy was well as selectivity were obtained by measuring the absorbance at the wavelength 200 nm than at 210 nm which was used in the original procedure.By modification of changing the determination wavelength to 200 nm,linear relationship between absorbance and concentration of NO-3 ion was obtained in the range of 0.05-3.00 mg·L-1 as shown by the linear regression equation y=0.006 6+0.715 5 x (r=0.999 8).Molar absorptivity of the proposed method was found to be 1.02×104L·mol-1·cm-1.It was found that NO-2 (<1.0 mg·L-1) and Cl- (<200 mg·L-1) were tolerable in the determination of NO-3 in different water samples.