Spin trapping for hydroxyl in water: a kinetic evaluation of two popular traps

Abstract

Two spin traps, 4-(N-methylpyridinium)tert-butyl nitrone (4-MePyBN) and 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) were examined for their effectiveness at trapping hydroxyl in water. At pH 6 and 22 °C, rate constants for trapping hydroxyl were found to be 0.5 × 109 M−1 s−1 (4-MePyBN) and 2.0 × 109 M−1  s−1 (DMPO). The hydroxyl adduct of DMPO decayed by a first order process with a half-life of 870 s. This was at least three times greater than that of the 4-MePyBN adduct. These and other results suggest that DMPO is the superior trap for this particular application and is well suited for use in biological systems.