Electron Spin Resonance (ESR) Study of Cigarette Smoke by Use of Spin Trapping Techniques

Abstract

The technique of spin trapping has been applied to the gas phase of cigarette smoke to identify and quantify the radicals present. It was found that radicals could be trapped only if the smoke was filtered. Three spin traps were used: N-tert-butyl-a-phenyl nitrone (PBN), 5,5-dimethyl-A'-pyrroline-l-oxide (DMPO) and a-43,5-di-tert-butyl-4-hydroxyphenyl)-N-tertbutyl nitrone (OHPBN). From the electron spin resonance 4ESR) splitting constants of the radicals produced by the reaction of smoke radicals with the spin traps and also from the effect of varying the path length between the cigarette and the spin trap solution, it is concluded that three types of signals are observed. Type I signals indicate the presence of oxygenated radicals which appear to be a mixture of alkoxy radicals RO and aroyloxy (ArCO2 I radicals. Our data do not allow conclusions about the nature of the R or Ar groups in these two oxy radicals; however, considerations based on lifetimes suggest that the R group probably is tertiary. Type II and III signals are not typical spectra of spin adducts. Instead, we believe they result from reaction of smoke land probably radicals in smoke) with the PBN spin trap and indicate that smoke has the ability to effect one-electron oxidations. Only type I signals are observed with DMPO and OHPBN. A quantitative study shows that 4 x 1014 spins/puff are present in the smoke, in contrast with the result of a recent study which used a very different method for determining the radical content of smoke.A discussion of the nature of the radicals in smoke and some tentative conclusions are presented.

Detection and Separation of Gas-Phase Carbon-Centered Radicals from Cigarette Smoke and Diesel Exhaust

“…Cigarette Smoke Sampling. The puff protocol was used to sample cigarette smoke. Using a 50-mL syringe, 35-mL puffs of 2-s duration were drawn from the cigarettes.…”

Superoxide Radical Anion Adduct of 5,5-Dimethyl-1-pyrroline N-Oxide (DMPO). 2. The Thermodynamics of Decay and EPR Spectral Properties

“…The nitrone 5,5-dimethyl-1-pyrroline N -oxide (DMPO) has been the most popular spin trap used in the detection and identification of transient radicals in chemical − and biological − systems using electron paramagnetic resonance (EPR) spectroscopy. Among the reactive oxygen species (ROS), the superoxide radical anion (O 2 •- ) has attracted considerable attention over the past 3 decades due to the crucial role it plays (along with nitric oxide (NO)) as a modulator of cellular functions such as in cell signaling, cell proliferation, or apoptosis .…”

Superoxide Radical Anion Adduct of 5,5-Dimethyl-1-pyrroline N-Oxide (DMPO). 1. The Thermodynamics of Formation and Its Acidity

“…Prior to 1974, the hydroperoxyl radical ( • O 2 H) could only be detected directly by EPR at low temperature or as a metal complex. , These approaches to radical detection limited the detection of superoxide (O 2 •- ) in biological systems, until DMPO was introduced for this purpose almost 3 decades ago by Harbor et al Subsequent detection of superoxide/hydroperoxyl (O 2 •- / • O 2 H) radicals in aqueous systems by EPR spin trapping using DMPO paved the way to exciting new findings in chemistry − and biology. − …”