Study of RP HPLC Retention Behaviours in Analysis of Carotenoids

For determination of selected carotenoids, various types of columns for high-performance liquid chromatography (HPLC) with different properties have been used. The characteristics of the laboratory-used packing material containing monomeric alkyl-bonded phases (C₁₈, C₃₀) and phenyl as well as phenyl-hexyl stationary phases were studied. The retention data of the examined compounds were used to determine the hydrophobicity and silanol activity of stationary phases applied in the study. The presence of the polar and carboxyl groups in the structure of the bonded ligand strongly influences the polarity of the stationary phase. Columns were compared according to methylene selectivity using a series of benzene homologues. The measurements were done using a methanol-water mobile phase. Knowledge of the properties of the applied stationary phase provided the possibility to predict the RP HPLC retention behaviours in analysis of carotenoids including lutein, lycopene and β-carotene. The composition of the mobile phase, the addition of triethylamine and the type of stationary phase had been taken into account in designing the method of carotenoid identification. Also a monolithic column characterised by low hydrodynamic resistance, high porosity and high permeability was applied. The presented results show that the coverage density of the bonded ligands on silica gel packings and length of the linkage strongly influence the carotenoid retention behaviours. In our study, the highest retention parameters for lutein, lycopene and β-carotene were observed for C₃₀ and C₁₈ stationary phase. This effect corresponds with pore size of column packing greater than 100 Å and carbon content higher than 11 %.