Detection of the reduced forms of radical adducts on the ESR trace using HPLC-electrochemical detector-ultraviolet absorption detector-electron spin resonance-MS

• Published in: Journal of separation science Vol. 33; no. 9; pp. 1185 - 1191
• Main Authors: Ikeda, Hideyuki, Iwahashi, Hideo
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley-VCH Verlag 01.05.2010; WILEY-VCH Verlag; WILEY‐VCH Verlag; Wiley
• Subjects: Adducts; Analytical chemistry; Chemistry; Chromatographic methods and physical methods associated with chromatography; Chromatography, High Pressure Liquid - methods; Electrochemistry - methods; Electron paramagnetic resonance; Electron spin resonance; Electron Spin Resonance Spectroscopy - methods; Exact sciences and technology; Free Radicals; Free radicals chemistry; HPLC-ECD-UV-ESR-MS; Mass spectra; Mass spectroscopy; Organic chemistry; Other chromatographic methods; Oxidation-Reduction; Pentyl radical; Phenyl radical; Phenylhydrazines - chemistry; Phenyls; Pyridines - analysis; Radicals; Reactivity and mechanisms; Reactors; Reduced forms of radical adducts; Spectrophotometry, Ultraviolet - methods; Spin trapping; Chemical analysis; Nitrone; Reaction product; EPR spectrometry; HPLC chromatography; Spin trapping; Electrospray; Electrochemical detector; Phenyl radical; HPLC-ECD-UV-ESR-MS; Ultraviolet detector; Reduced forms of radical adducts; Phenyl radicals; Pentyl radicals; Reduced state; Pentyl radical; Copper II Chlorides; Mass spectrometry; Molecular adduct; Organic hydroxylamine
• ISSN: 1615-9306; 1615-9314
• DOI: 10.1002/jssc.200900731

To detect and identify the electron spin resonance (ESR) silent forms of the α-(4-pyridyl-1-oxide)-N-tert-butylnitrone (4-POBN) radical adducts, an electrochemical detector (ECD) was employed as a reactor in the HPLC-ECD-UV absorption detector-ESR-MS (HPLC-ECD-UV-ESR-MS). The ECD was employed to regenerate the radical forms from the reduced forms. The reduced forms of the 4-POBN/pentyl radical adducts were analyzed using the HPLC-ECD-UV-ESR-MS. On addition of the ECD applied potential of +0.3 V, a peak appeared on the ESR trace of the HPLC-ECD-UV-ESR-MS analyses, indicating that the radical forms are regenerated from the reduced forms. The HPLC-ECD-UV-ESR-MS analyses were also performed for the reaction mixtures of phenylhydrazine with CuCl₂. Two peaks (peaks I and II) were detected on the UV trace (300 nm) of the HPLC-ECD-UV-ESR-MS. The mass spectra showed that the peak I and peak II compounds are radical and reduced forms of the 4-POBN/phenyl radical adducts under the ECD applied potential of 0.0 V. Peak I was only detected on the ESR trace under the ECD applied potential of 0.0 V. In addition to peak I, peak II appeared on the ESR trace under the ECD applied potential of +0.3 V, indicating that the reduced forms are oxidized to the corresponding radical forms.