The separation of geometric and positional isomers is a challenging task in reversed phase chromatography.
Subtle molecular differences have to be recognised and resolved by the particular stationary phase. Sander et al. have shown conclusively that polymeric C30 HPLC stationary phases are able to discriminate isomeric structures of long chain molecules [1,2].
Retention behaviour
Compared to classical C18 stationary phases, YMC30 is much more hydrophobic. Even when pure organic eluents are applied, many sample solutes are retained.
The YMC30 stationary phase provides sufficient phase thickness to enhance interaction with long chained molecules (fig. 1). Therefore, geometric and positional isomers of conjugated double bonding systems are recognised and resolved by the YMC30 phase. The resolving power of YMC30 for isomers can be verified by the separation of carotenoids, which has been subject of considerable research efforts in the past [1,2].
Carotenoids are found in a variety of natural sources including fruits and vegetables. In addition, carotenoids are considered as potential drugs for cancer intervention or prevention. Despite the complexity of carotenoid extracts and the minor shape differences between carotenoid isomers, the separation, identification and quantification of these compounds can be achieved by using YMC30 columns. |
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Fig. 1: Comparison of the film thickness of C18 and C30 stationary phases with the molecular length of β-carotene (determined with Small Angle Neutron Scattering (SANS)). |
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References
[1] Sander, L.C. and S.A. Wise; J. Chromatogr. 1993, 656, 335-351
[2] Sander, L.C. et al.; Anal. Chem. 1994, 66, 1667-1674
Column care
Good separations have been achieved with typical non-aqueous reversed phase mobile phases. To
prevent a loss in selectivity by the reversible folding of C30 chains, a high water content of the eluent has
to be avoided. The recommended pH range for using YMC30 columns is 2-6. Remove acid and buffer
salts before storage. Store the column in 100% methanol. Clogged inlet frits can be cleaned by changing
the flow direction or replacement.
For detailed information please refer to the “Column Care and Use Instructions”, which are shipped with
each analytical column.
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