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Investigation of the Presence of OH Radicals in Electrolyzed NaCl Solution by Electron Spin Resonance Spectroscopy

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Department of Food Science and Technology, Oregon State University, 100 Wiegand Hall, Corvallis, Oregon 97331, and Department of Environmental and Occupational Health Sciences, University of Washington, 4225 Roosevelt Way NE 100, Seattle, Washington 98105
Cite this: J. Agric. Food Chem. 2005, 53, 12, 4901–4905
Publication Date (Web):May 11, 2005
Copyright © 2005 American Chemical Society

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    In the anode side of a two-chamber electrolyzer, electrolysis of a NaCl solution generates acidic electrolyzed oxidizing (EO) water, which exhibits bactericidal effects against a large number of pathogens. This study was undertaken to investigate whether OH radical species are present in EO water or are formed when EO water reacts with iron ions. Electron spin resonance spectroscopy (ESR) coupled with the spin trapping technique was used for the detection of free radicals. Samples of EO water were collected at 0.5, 1, 2, 3, and 5 min of electrolysis and immediately mixed with the spin trapping agent 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). The 5,5-dimethyl-2-hydroxypyrrolidine-N-oxyl (DMPO-OH) spin adduct, characteristic of OH radicals, was not observed. Starting with 2-min electrolysis, a seven-line spectrum characteristic of 5,5-dimethyl-2-pyrrolidone-N-oxyl (DMPOX) was formed. The reactions of EO water with Fe3+ and Fe2+ in the presence of DMPO yielded the spin adduct DMPO-OH. However, the addition of OH radical scavengers (ethanol and methanol) did not generate the characteristic DMPO-alkyl spin adducts. This indicated that the DMPO-OH spectrum was due to a nucleophilic addition of water to DMPO and not to trapping of OH radicals.

    Keywords: Electrolyzed water; DMPO; DMPO-OH; iron; electron spin resonance spectroscopy


     Present address:  Department of Pharmacology and Physiology, Drexel University College of Medicine, 245 N 15th Street, NCB, MS488, Philadelphia, PA 19102.

     Oregon State University.

     University of Washington.


     To whom correspondence should be addressed. Telephone:  541-737-6519. Fax:  541-737-1877. E-mail:  [email protected].

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