Thiyl Radical-Based Charge Tagging Enables Sterol Quantitation via Mass Spectrometry
2017-11-20T00:00:00Z (GMT)
by
Inspired
by the high reactivity and specificity of thiyl radicals
toward alkenes, we have developed a new charge derivatization method
to enable fast and quantitative analysis of sterols via electrospray
ionization-mass spectrometry (ESI-MS). Thioglycolic acid (TGA), a
commercially available compound, has been established as a highly
efficient tagging reagent. Initiated from photochemical reactions,
the thiyl radical derived from TGA abstracts an allylic hydrogen in
the B ring of sterols, forming a radical intermediate which rapidly
recombines with a second thiyl radical to produce the final tagged
product. Because of the incorporation of a carboxylic acid group,
TGA tagging not only improves the limit of detection (sub-nM) for
sterols but also facilitates their quantitation via characteristic
44 Da neutral loss scan. This radical based derivatization is fast
(1 min) and efficient (>90% yield) when conducted in a flow microreactor.
The analytical utility of thiyl radical charge tagging method has
been demonstrated by quantifying sterols from human plasma and vegetable
oil.