An ethanol-(NH4)2SO4 aqueous two-phase system has been applied to the extraction and spectrophotometric
determination of nitrite. The complex formed by nitrite and methyl orange was extracted to the upper ethanol
phase and was measured at 432 nm. The concentration of nitrite varies linearly with the absorbance over the
range of ~0.5–6.0 mg/l. The proposed method has been applied to the determination of nitrite in food samples. The
analytical results obtained by this method and the naphthyl ethylenediamine spectrophotometric method were in
good agreement.