The comparison analysis of nitrate nitrogen determination is conducted with the same standard solution and natural water samples by two methods of spectrophotometric method with phenol disulfonic acid and ultraviolet spectrophotometer.

By the way of spectrophotometric method with phenol disulfonic acid monitoring nitrate nitrogen in water, the concentration of standard solution will reduce by the reason of error brought by the processing of drawing standard curve.

Two simple and quick methods of the determination of nitrate nitrogen in water were discussed,the result showed that nitrate radical potentio metric analysis determinates nitrate nitrogen in water,it had more higher accuracy,precision and anti-interference than phenol disulfonic acid spectrophotometry.

The determining results were compared with that of national standard test (disulfonic acid phenol method).

This text make use of the phenol disulfonic acid colorimetry,investigate the detemination in vegetable of daily life,-show people's increasing knowledge about food quantity and paying more attention on it.

By using spectrophotometric method with phenol disulfonic acid as major reagent and introduced as standard liquid in determining nitrate nitrogen,the preparation conditions can have a great influence on the results.