PERIODATE-CATALYZED OXIDATIVE COUPLING OF ANILINE-DERIVED P-AMINOPHENOL WITH P-XYLENOL AS A DETECTION METHOD FOR HYDROXYL RADICALS

Abstract

A simple spectrophotometric method for rapid detection of hydroxyl radical (^•OH) has been developed. The principle of the method depends upon the hydroxylation of a trapping agent, aniline, by ^•OH leading to the formation of various hydroxylated products. One of these hydroxylated products, p-aminophenol (PAP), is capable of undergoing an oxidative coupling reaction with p-xylenol (2,5-dimethylphenol) catalyzed by sodium periodate. The resultant indophenol-derivative formed can be measured spectrophotometrically at 635 nm. The net increment of absorbance at 635 nm can then be used to estimate the degree of hydroxylation of aniline, which is dependent upon the amount of ^•OH present in the assay system. A specific example for estimating the ^•OH-scavenging abilities of food products is also given.

Keywords:

• Hydroxyl radical
• Oxidative coupling
• P-aminophenol

ACKNOWLEDGMENTS

The work is partially supported by a grant from National Science Council of the Republic of China (grant # NSC 89-2314-B-242-003 to TZL).