Preparation, characterization, and separation mechanism of a dehydroabietic-acid-based shape-selective chromatographic stationary phase1.

ABSTRACT

Chromatographic stationary phases with molecular-shape selectivity are advantageous for the separation and analysis of geometric isomers. Herein, dehydroabietic acid is bonded on the surface of silica microspheres via 3-glycidoxypropyltrimethoxysilane to form a monolayer dehydroabietic-acid stationary phase (Si-DOMM) with a racket-shaped structure. Various characterization techniques indicate that Si-DOMM is successfully prepared, and the separation performance of a Si-DOMM column is evaluated. The stationary phase has a low silanol activity and metal contamination and a high hydrophobicity and shape selectivity. The resolutions of lycopene, lutein, and capsaicin on the Si-DOMM column confirm that the stationary phase exhibits high shape selectivity. The elution order of n-alkyl benzene on the Si-DOMM column indicates its high hydrophobic selectivity and suggests that the separation is an enthalpy-driven process. Repeatability experiments reveal highly stable preparation processes of the stationary phase and column and indicate that the relative standard deviations of retention time, peak height, and peak area are less than 0.26%, 3.54%, and 3.48%, respectively. Density functional theory calculations using n-alkylbenzenes, polycyclic aromatic hydrocarbons, amines, and phenols as model solutes provide an intuitive and quantitative description of the multiple retention mechanisms. The Si-DOMM stationary phase exhibits superior retention and high selectivity for these compounds via multiple interactions. The bonding phase of the monolayer dehydroabietic acid stationary phase with a racket-shaped structure has a unique affinity for benzene, strong shape selectivity, and good separation performance for geometrical isomers with different molecular shapes.