SPECTROPHOTOMETRIC DETERMINATION OF NITRITE IN WATER SAMPLES USING RESPONSE SURFACE METHODOLOGY

The present paper seeks to develop a simple and economical method for the spectrophotometric determination of nitrite based on its diazotization-coupling reaction with 4-amino-3-hydroxynaphthalene-1-sulfonic acid (AHNSA) with concentration of 0.00076 mol L-1 and 1-Naphthylamine (1-NA) with concentration of 0.001 mol L-1 in hydrochloric acid with concentration of 1.0 mol L-1. The behavior of various factors which affect the reaction i.e. concentration of hydrochloric acid, AHNSA and 1-NA were investigated by central composite design (CCD) as a response surface method. Beer's law was found to be followed in two concentration range of nitrite as 0.01-0.90 mg L−1 and 1.0-8.5 mg L−1 at 347 and 394 nm, respectively. The approach was applied to determine nitrite at low mg L−1 levels with satisfactory statistics in rain, tap and wastewater samples. The RSD in determination of nitrite in real samples is lower than 10%.