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Single‐sweep polarographic determination of ammonia by its reaction with 1‐naphthol and hypochlorite
Author(s) -
Zhao Zaofan,
Mo Jianwei
Publication year - 1990
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/elan.1140020210
Subject(s) - polarography , saturated calomel electrode , chemistry , dropping mercury electrode , ammonia , hypochlorite , disproportionation , inorganic chemistry , electrode , electrochemistry , reference electrode , catalysis , organic chemistry
A polarographic procedure is described for the determination of ammonia at concentration levels below 10 −4 M that is based on its reaction with 1‐naphthol and hypochlorite in a strongly alkaline medium whose (1,4‐indonapthol) product is polarographically active. The polarographic behavior of the compound and the electrode process has been studied by several electrochemical methods. The experimental results showed that it is an EC process involving the formation of a radical as the electrode product that is followed by a disproportionation reaction of the radical. The rate constant ( k f ) of the coupled following chemical reaction was found to be 0.228 s −1 . The wave height at −0.47 V [versus the standard calomel electrode (SCE)] on the dropping mercury electrode (DME) is directly proportional to the concentration of ammonia from 1 × 10 −7 to 5 × −5 M, and the detection limit is 5 × 10 −8 M. A mercury film electrode can also be used for the determination of ammonia. The method has been applied to the analysis of water and serum samples.