Determination of sulfite in water samples by flow injection analysis with fluorescence detection

A fast, sensitive, and reliable method for the determination of sulfite (SO₃²⁻) in fresh water and seawater samples was developed. The proposed method was based on the reaction of o-phthalaldehyde (OPA)–sulfite–NH₃ in alkaline solution, with flow injection analysis and fluorescence detection. The experimental parameters were investigated in pure water and seawater matrixes. The detection limits (S/N = 3) were 0.006 μmol/L in pure water and 0.018 μmol/L in seawater for SO₃²⁻. The method was successfully applied to analyze SO₃²⁻ in the samples of rain water and flue gas desulfurization seawater.