Determination of Nitrite by a New Spectrophotometric Method Using Safranin

Abstract

A spectrophotometric method was developed to determine nitrite using safranin as color reagent. The reaction between nitrite and safranin produces a safranin-HNO₂ species, which exhibits absorption peaks at 280, 349, 420(shoulder) and 610 nm. The peak at 610 nm was chosen as the analysis wavelength because nitrite ion and safranin do not present absorption bands in this region. The Lambert-Beer law was obeyed in the concentration range 7.0 × 10⁻⁶ - 5.0 × 10⁻⁵M. The effects of various ions on absorbance of the safranin-HNO₂ species were studied; the nitrite analysis can be performed without interference in the presence of the ions SCN⁻, Br⁻, CH₃COO⁻, Cl⁻ (≤ 1.0 × 10⁻³ M) and NO₃ ⁻ (< 1.0 × 10⁻⁵ M). The SO₄ ⁼ does not interfere even at a concentration of 0.25M.

Key Words:

• safranin
• spectrophotometric method
• nitrite