Carotenoids mass spectrometry

Other spectroscopic methods such as infrared (ir), and nuclear magnetic resonance (nmr), circular dichroism (cd), and mass spectrometry (ms) are invaluable tools for identification and stmcture elucidation. Nmr spectroscopy allows for geometric assignment of the carbon—carbon double bonds, as well as relative stereochemistry of ring substituents. These spectroscopic methods coupled with traditional chemical derivatization techniques provide the framework by which new carotenoids are identified and characterized (16,17). 

When the aim is isolation for identification by direct probe insertion mass spectrometry (MS), plastic materials, filter papers, and blenders should be avoided to prevent contamination during extraction and chromatography. It is also very important to avoid the cis-trans isomerization of carotenoids in solution, which is accelerated by heat, light, acids, and active surfaces. Therefore, a pure carotenoid or even a crude extract should never be stored in solution it should be kept completely dry in an inert atmosphere at low temperature. 

Li, H. et ah. Determination of carotenoids and all-fra 5-retinol in fish eggs by liquid chromatography-electrospray ionization-tandem mass spectrometry, J. Chromatogr. B, 816, 49, 2005. 

Enzell, C.R. and Back, S., Mass spectrometry, in Carotenoids Spectroscopy, IB, Britton, G., Liaaen-Jensen, S., and Pfander, H., Eds., Birkhanser, Basel, 1995, 261. 

Enzell, C.R., Francis, G.W., and Liaaen-Jensen, S., Mass spectrometric studies of carotenoids. 2. Survey of fragmentation reactions, Acto Chem. Scand., 3, 727, 1969. Van Breemen, R.B., Schmitz, H.H., and Schwartz, S.J., Fast atom bombardment tandem mass spectrometry of carotenoids, J. Agric. Food Chem., 43, 384, 1995. 

Van Breemen, R.B., Electrospray liquid chromatography-mass spectrometry of carotenoids, Anal. Chem., 67,2004, 1995. 

Van Breemen, R.B. et al.. Liquid chromatography/mass spectrometry of carotenoids using atmospheric pressure chemical ionization, J. Mass Spectrom., 31, 975, 1996. Tian, Q., Duncan C.J.G., and Schwartz S. J., Atmospheric pressure chemical ionization mass spectrometry and in-source fragmentation of lutein esters, J. Mass Spectrom., 38, 990, 2003. 

Because of their considerable role in human wellfare, carotenoids have been measured not only in plants as primary sources and in human and animal tissues but also in a wide variety of other matrices to find new and economical sources for carotenoids. Thus, the carotenoid accumulation capacity of algae and microalgae have been vigorously investigated. A validated liquid chromatography-electrospray mass spectrometry method have been developed and employed for the separation and quantitative determination of... 

This review will first concentrate on the unimolecular gas-phase chemistry of diene and polyene ions, mainly cationic but also anionic species, including some of their alicyclic and triply unsaturated isomers, where appropriate. Well-established methodology, such as electron ionization (El) and chemical ionization (Cl), combined with MS/MS techniques in particular cases will be discussed, but also some special techniques which offer further potential to distinguish isomers will be mentioned. On this basis, selected examples on the bimolecular gas-phase ion chemistry of dienes and polyenes will be presented in order to illustrate the great potential of this field for further fundamental and applied research. A special section of this chapter will be devoted to shed some light on the present knowledge concerning the gas-phase derivatization of dienes and polyenes. A further section compiles some selected aspects of mass spectrometry of terpenoids and carotenoids. 

The elimination of arenes is not limited to the radical cations of the carotenoids. Just as the neutral compounds themselves also tend to undergo (thermal) cyclization followed by arene loss, the protonated analogues, e.g. ion 82 generated by Cl or fast atom bombardment (FAB) mass spectrometry are prone to eliminate one or even two arene molecules as well (Scheme 26)270. 

Several original papers must be mentioned that deal with mass spectrometric techniques which the numerous reviews do not comprise. Kaufmann and coworkers268,288 studied the mass spectrometric analysis of carotenoids and some of their fatty acid esters using matrix-assisted laser desorption/ionization (MALDI) mass spectrometry and its post-source-decay (PSD) variant. Some advantages concerning the thermal instability and limited solubility were discussed, but the fragmentation paths of the carotenoid cations were found to be essentially the same as those observed with conventional techniques. 

Basic Protocol 2 Fast Atom Bombardment, Liquid Secondary Ion Mass Spectrometry, and Continuous-Flow Fast Atom Bombardment of Carotenoids F2.4.2... 

ELECTRON IMPACT AND CHEMICAL IONIZATION MASS SPECTROMETRY OF CAROTENOIDS... 

Mass Spectrometry of Carotenoids NOTE For LC/MS or flow injection using continuous-flow FAB, the mass spectrometer must be equipped with a continuous-flow ionization source. 

For example, the ion of [M-69]+, which is observed in the tandem mass spectra of lycopene, neurosporene, and y-carotene but not a-carotene, p-carotene, lutein, or zeaxanthin, indicates the presence of a terminal acyclic isoprene unit. Elimination of a hydroxyl group or a molecule of water, [M-17]+ or [MH-18]+, from carotenoids such as astaxanthin or zeaxanthin is characteristic of the presence of a hydroxyl group. Also, tandem mass spectrometry can be used to distinguish between isomeric carotenoids such as a-carotene and p-carotene, or lutein and zeaxanthin. For example, the ring of a-carotene containing the double bond that i s not conj ugated to the rest of the polyene chain shows unique retro-Diels-Alder fragmentation to form the ion of [M-56]+. In a similar manner, isomeric lutein and zeaxanthin differ by the... 

Kaufmann, R., Wingerath, T., Kirsch, D., Stahl, W., and Sies, H. 1996. Analysis of carotenoids and carotenol fatty acid esters by matrix-assisted laser desorption ionization (MALDI) and MALDI-post-source-decay mass spectrometry. Anal. Biochem. 238 117-128. 

S. J. 1992. Applications of fast atom bombardment mass spectrometry (FAB-MS) and continuous-flow FAB-MS to carotenoid analysis. Methods Enzymol. 213 322-336. 

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