Collision Cross-Section Determination and Tandem Mass Spectrometric Analysis of Isomeric Carotenoids Using Electrospray Ion Mobility Time-of-Flight Mass Spectrometry

摘要

Carotenoids are natural pigments with provitamin A andnantioxidant activities. Biosynthesized in plants as their alltransnisomers, carotenoids isomerize in solution and innhumans to multiple cis isomers which can have differentnbioavailabilities and functions. Since separation andncharacterization of isomeric carotenoids using high-pressurenliquid chromatography (HPLC) or liquid chromatography-ntandem mass spectrometry (LC-MS/MS) is timeconsuming,nthe potential for ion mobility mass spectrometryn(IM-MS) to resolve and characterize carotenoidnisomers rapidly without chromatography was investigatednusing traveling-wave ion mobility spectrometry on a quadrupolentime-of-flight mass spectrometer. The all-transnisomers of lycopene and u0001-carotene were separated bynseveral milliseconds from the cis-isomers which werendetected as partially overlapping peaks. The collisionncross-section values of these carotenoid isomers werendetermined using IM-MS to be 180 and 236 Å2 for cislycopenenand all-trans-lycopene, and 181 and 225 Å2nfor cis-u0001-carotene and all-trans-u0001-carotene, respectively.nCollision-induced dissociation MS/MS of ion mobilityresolvednisomers indicated that cis and all-trans carotenoidnisomers can be distinguished by their fragmentationnpatterns. Previous MS/MS studies of cis- andnall trans-carotenoids had suggested that they producednidentical tandem mass spectra, but this appears tonhave been the result of isomerization during ionization.nIntroduction of specific cis or trans isomers by infusionnor HPLC resulted in cis/trans isomerization in the ionnsource during electrospray, and the relative levels ofncis carotenoids forming in the ion source comparednto the all-trans isomers were temperature dependent.