Add time:07/25/2019         Source:sciencedirect.com

A method for analysing traces of nitrites is described. The method is based on the diazotization of a heteroaromatic primary amine—4-methyl-7-aminocoumarin (Coumarin 120®)—by nitrite ions in acidic medium. A large excess of Coumarin 120® is mandatory for a quantitative reaction. The corresponding in-situ-produced diazonium salt is stable at room temperature and can be selectively isolated in the aqueous layer by extraction of the excess of unreacted Coumarin 120® with ethyl acetate. The hydrolysis of the diazonium salt at 100 °C yields a fluorescent product, 4-methyl-7-hydroxycoumarin (4-methylumbelliferone), which is measured by direct spectrofluorimetry (λex = 325 nm; λem = 380 nm). In this way levels of nitrites in water samples as low as 10 μg 1−1 can be easily quantified.

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