Carotenoid thermal instability

TLC methods were employed to isolate 12 carotenoid compounds by Isaksen and Francis.57 To date, TLC is often used as the first identification step for carotenoids. GC is almost never applied for carotenoid analysis due to carotenoids thermal instability. 

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. 

This chapter has focused almost exclusively on the electronic structures and dynamics associated with carotenoids in all-trans configurations. Although all-trans carotenoids often are selected by lightharvesting complexes, c/x-isomers tend to be employed by photosynthefic reaction centers, and it is important to understand both how the energetics and the kinetics are modified for cis conformers. One obvious problem in carrying out such studies, at least in vitro, is the thermal and photochemical instability of the cis forms. Nevertheless, the importance of these isomers in vision and in photoprotection provides strong motivation for extending spectroscopic and time-resolved studies to these systems. 

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