ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

A novel kinetic-spectrophotometric method for determination of nitrites in water

Zenovia Moldovan

Department of Analytical Chemistry, University of Bucharest, Faculty of Chemistry, 90-92 Panduri Road, 050663 Bucharest, Romania

E-mail: z_moldovan@yahoo.com

Received: 27 October 2008  Revised: 7 December 2008  Accepted: 9 December 2008

Abstract: A simple, selective and sensitive kinetic method for the determination of nitrite in water was developed. The method is based on the catalytic effect of nitrite on the oxidation of methylene blue (MB) with bromate in a sulfuric acid medium. During the oxidation process, absorbance of the reaction mixture decreases with the increasing time, inversely proportional to the nitrite concentration. The reaction rate was monitored spectrophotometrically at λ = 666 nm within 30 s of mixing. Linear calibration graph was obtained in the range of 0.005–0.5 μg mL⁻¹ with a relative standard deviation of 2.09 % for six measurements at 0.5 μg mL⁻¹. The detection limit was found to be 0.0015 μg mL⁻¹. The effect of different factors such as acidity, time, bromate concentration, MB concentration, ionic strength, and order of reactants additions is reported. Interference of the most common foreign ions was also investigated. The optimum experimental conditions were: 0.38 mol L⁻¹ H₂SO₄, 5 × 10.4 mol L⁻¹ KBrO₃, 1.25 × 10.5 mol L⁻¹ MB, 0.3 mol L⁻¹ sodium nitrate, and 25°C. The proposed method was conveniently applied for the determination of nitrite in spiked drinking water samples.

Keywords: nitrite ion - catalytic - methylene blue - spectrophotometry - water sample

Full paper is available at www.springerlink.com.

DOI: 10.2478/s11696-009-0038-2

Chemical Papers 63 (4) 385–390 (2009)