Aqueous two-phase extraction and spectrofluorimetric determination of nitrite with o-phenylenediamine enhanced by hydroxypropyl-β-cyclodextrin in urine samples

An aqueous two-phase extraction process composed of tetrahydrofuran/ammonium sulfate to extract nitrite from urine samples is investigated. The method is based on the reaction of nitrite with o-phenylenediamine in acid media to form benzotriazole and the aqueous two-phase extraction of benzotriazole in the presence of salt as an inducing agent in phase separation, followed by spectrofluorimetric detection. The system of fluorescence intensity was enhanced by complexation of hydroxypropyl-beta-cyclodextrin. The optimal reaction and extraction conditions were studied. The linear calibration range for nitrite was 5-1000 ng mL(-1) with a detection limit of 1.5 ng mL(-1) (S/N = 3). The relative standard deviations for six replicate measurements varied between 0.3% and 1.7%. The interference effects of some anions and cations were also tested. The proposed method was successfully applied for the determination of nitrite in the urine samples with recoveries of 93.3% to 105.0%.