Application of tandem mass spectrometry in analysis of carotenoids

Carotenoids are a group of naturally occurring polyene pigments with antioxidant activities. A review of recently published studies of these molecules using tandem mass spectrometry is presented here. The atmospheric pressure ionization sources used in conjunction with the tandem MS systems produced a plethora of differing ions ranging from molecular ions to acid-base exchange of protons and/or ligand exchange such as formation of sodium adduct. The triple quadrupole MS systems (QQQ) were the instrument choice for the quantitation studies. The high degree of specificity associated with the QQQ MS systems sufficiently resolved the isobaric interferences, but was not adequate to resolve some isomeric forms such as various lycopene geometrical isomers. The separation of the isomeric forms of the carotenoids still required careful optimization of chromatographic method. Triple quadrupoles were also used in identification of degradation products by an in-vitro predictive approach. A study of collision induced fragmentation pattern of several isomeric species of carotenoids in a QQQ MS system revealed that the fine spectral details and differences virtually disappeared by increasing the collision energy.