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Sequential injection spectrophotometric analysis of nitrite in natural waters using an on-line solid-phase extraction and preconcentration method

“…In these cases, preconcentration methods are required, among them FIA systems based on the indirect nitrite determination by liquid-liquid extraction 28 or the use of chromatomembrane cells. 29 Another alternative is solid-liquid extraction. The azo dye resulting from the diazotizationcoupling reaction has been preconcentrated on either anionic exchange resins (Dowex 1-X8) 30 or on ion pairs coprecipitated with microcrystalline biphenyl 31,32 or with naphthalene.…”