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Simultaneous Electroanalysis of Hypochlorite and H 2 O 2 : Use of I − /I 2 as a Probing Potential Buffer
Author(s) -
Awad Mohamed Ismail,
Sata Shunsuke,
Ohsaka Takeo
Publication year - 2005
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.200403151
Subject(s) - oxidizing agent , hydrogen peroxide , chemistry , selectivity , hypochlorite , inorganic chemistry , potentiometric titration , redox , sodium hypochlorite , buffer solution , detection limit , electrode , molybdate , buffer (optical fiber) , catalysis , chromatography , organic chemistry , telecommunications , computer science
Sodium hypochlorite (NaClO) and hydrogen peroxide (H 2 O 2 ) have been simultaneously analyzed, for the first time, using a simple and rapid potentiometric method. The present method shows a high sensitivity, selectivity and satisfactory reproducibility. Pt electrode was used as an indicator electrode and the I 2 /I − redox couple was used as a probing potential buffer. The large difference in the rates of the oxidation of I − by the two oxidizing agents, that is, the oxidation of I − by NaClO is by several orders of magnitude faster than that by H 2 O 2 , enabled the selective analysis of these two species. Based on such a large difference in the rates, a momentary potential response corresponding to the oxidation of I − by NaClO and another quite slow one by H 2 O 2 could be obtained. Factors affecting the selectivity as well as the sensitivity, such as the concentrations of molybdate (used as catalyst for the oxidation of I − by H 2 O 2 ), H + , I 2 , and I − in the potential buffer were examined. The expected Nernstian responses were obtained over a considerable range of the concentrations of the two oxidizing agents with slopes of 30.5 and 29.9 mV for NaClO and H 2 O 2 , respectively (in a close agreement with the theoretical value, that is, 29.6 mV) and with a detection limit in the submicromolar range (0.2 μM).