Abstract

In order to control the pollution by nitrate, a simple, accurate and sensitive reverse flow injection analysis (rFIA) spectrophotometric method for determination of nitrate in tannery effluent is proposed in this paper. Firstly, in alkaline medium and with copper ion as catalyst, nitrate is reduced to nitrite by hydrazine sulfate. Then in acid condition, nitrate and sulfanilamide are diazotized. The diazo material is then coupled with N-1-naphthyl ethylenediamine hydrochloride (NEH) to form a red product. The absorbance of the complex compounds is measured at 540nm. Chemical factors and rFIA variables affecting the system are also discussed. Under the optimal conditions, the linear range of this method was 50-5000μg l-1; the detection limit was 7μg l-1; the relative standard deviation was 0.844%. This method was suitable for automatic and continuous analysis, and successfully applied to determine the content of nitrate in tannery effluent.