An Artifact in the ESR Spectrum Obtained by Spin Trapping with Dmpo

Abstract

In order to overcome a common problem in spin trapping with high concentrations of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) where ESR spectra are obtained which include an unidentified set of lines composed of a triplet of doublets, commercial DMPO was analyzed for its impurities by high-performance liquid chromatography, mass spectrometry, and nuclear magnetic resonance spectroscopy. It has been determined that this undesirable ESR spectrum is due to an impurity included in the spin trap. This compound has been assigned to the hydroxylamine which is a DMPO-derivative having an epoxy ring located at the 2 and 3 positions.