Electrochemical oxidation of lipids followed by MS detection shows great potential for fast mimicking of enzymatic (CYP450) and radical-induced peroxidation reactions. The applicability of on- and off-line Electrochemistry/MS is broad, ranging from studying food oxidation to implications of lipid oxidation on human health (oxidative stress).
With boron-doped diamond as a working electrode (Magic Diamond - Antec), hydroxyl radicals (OH•) , known as the most reactive oxygen species (ROS), can be the generated on the fly, allowing for the controlled oxidation of fatty acids, cholesterol, etc., prior to introduction into the MS.
Furthermore, EC/MS allows studying secondary reactions such as the effect of antioxidants on food products or crosslinks with non-lipids such as proteins or DNA.
Oxysterols are formed in vivo by enzymatic and non-enzymatic oxidation of cholesterol. Here the generation of numerous cholesterol oxidation products in short reaction times are shown using the ROXY EC system (Antec).
(A) Schematic representation of the ROXY EC system (consisting of syringe pump, ROXY potentiostat equipped with μ-PrepCell) coupled to ESI-MS
(B) mass spectra acquired with ESI-LTQ-Orbitrap XL MS in positive ion mode of a 100 μmol/L cholesterol solution with EC-cell OFF
(C) EC-cell ON. Protonated ion species, sodium- and methanol-adducts are shown
The electrochemically generated oxysterols show excellent agreement with the known enzymatic biotransformation reactions and with some of the radical-driven reactions. To read more, click here.
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Fatty acid methyl esters (FAME) are the primary constituents of biodiesel. During prolonged storage, they can easily undergo oxidation.
The oxidation products may lead to deposits and coking in vehicles. Electrochemical (EC) oxidation has been applied as a surrogate system for monitoring FAME oxidation. The EC cell is coupled on-line to an ESI-TOF-MS and has proved to be an excellent technique for fast monitoring of the oxidation reactions (ca. 10 min), without pre-treatment of samples and no need for chromatographic separation. To read more, click here.
(A) EIC of the sodiated C18:3 (m/z 315) and example of their oxidation product (m/z 393)
(B) Mass spectrum corresponding to the time window indicated by the green arrow with EC cell on
201500101 - Electrochemical oxidation of cholesterol: An easy way to generate numerous oxysterols in short reaction times
D Weber, Z Ni, D Vetter, R Hoffmann, M Fedorova; Eur. J. Lipid Sci. Technol. 2016, 118, 325-331
201500219 - Generation of oxysterols formed by free radicals and enzymes by electrochemical oxidation
G Lizard; Eur. J. Lipid Sci. Technol. 2016, 118, 135-136
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