Determination of Nitrite and Nitrate by Forming Two 8-Hydroxyquinoline Based Azo Dyes

two sensitive and selective spectrophotometric methods are presented for the determination of trace amounts of nitrite and nitrate. it relies on the reaction of nitrite with sulfadimidine (sd) and cisapride (cp) in acidic medium to form diazonium ions, which are coupled with 8-hydroxyquinoline (hq) in basic solutions to form the related azo dyes. absorbances were measured at 507 nm for sd-hq product and at 532 nm for cp-hq product. the calibration curves were linear in the ranges of 0.05-2.5 and 0.04-5.0 mg l-1 for sd-hq and cp-hq systems, respectively. the relative standard deviations for the nitrite determination methods were obtained as 0.3-0.9% and 0.1-0.8% for sd-hq system and cp-hq system, respectively. nitrate was also determined after using a cadmium-copper reducing column. interferences of various foreign ions were tested and the methods were successfully applied to the determination of nitrite and nitrate in various water samples.