Mechanistic Aspects of Chiral Discrimination on a Molecular Imprinted Polymer Phase

Abstract

The mechanism of chiral selectivity of a difunctional polymer imprinted with dansyl-L-phenylalanine was investigated using the polymer as an HPLC stationary phase. Temperature studies revealed that the mass transfer of the imprinted enantiomer with the polymer was sluggish at low temperatures, leading to a nonequilibrium migration down the column. Conversely, retention of the non-imprinted enantiomer was controlled by a thermodynamic equilibrium over the entire temperature range of the study. Variation of the structure of the analyte indicated a single leading interaction between both enantiomers of dansyl-phenylalanine and the polymer phase; a hydrogen bonding interaction between the carboxylic acid group of dansyl-phenylalanine and pyridinyl sites on the polymer. Downloaded by [Southern Illinois University] at 08:01 20 December 2014 ORDER REPRINTS 184 O'BRIEN ET AL.Secondary processes contributing to enantioselectivity were also deduced; a hydrogen bonding interaction occurring between the imprinted enantiomer and carboxyl sites on the polymer and a precise steric fit of the amino acid side chain into the imprinted sites.Studies varying the mobile phase hydrogen bond competitor agree with the results obtained by the structural studies.

Chiral recognition ability of an (S)‐naproxen‐ imprinted monolith by capillary electrochromatography

“…This result was coincident with Lin et al [22]. It has been reported that the mass transfer of the imprinted enantiomer with the polymer was sluggish at low temperatures, leading to a nonequilibrium migration down the column [23]. On the contrary Schweitz et al [20] performed all experiments at 607C.…”

Deviation from van't Hoff dependence in RP‐LC induced by tautomeric interconversion observed for four compounds

“…In Fig. 3 the tautomeric forms of drotaverine together with their calculated log D ow are depicted [8]. As can be observed the enamine-type tautomeric form (b) is the most hydrophobic structure, with a calculated log D ow 5 2.71, almost double than amino form.…”

“…This behavior has been already observed by thermodynamic studies achieved for chiral separations, when the van't Hoff plots of data obtained by separating enantiomers of a conformationally rigid spirolactam or β‐blockers on a commercial liquid chromatographic column packed with a stationary phase derived from ( R )‐ N ‐(3,5‐dinitrobenzoyl)phenylglycine were non‐linear 6, 7. Deviation from linearity has been observed for the chiral separation mechanism of difunctional polymer imprinted with dansyl‐ L ‐phenylalanine as stationary phase 8. Keto‐enolic tautomerism resulting in its keto and enol forms of chlortetracycline posed problems in developing an LC‐MS/MS method for determining this antibiotic in pig tissues.…”

GC–MS Study of the formation of alkoxysilanes from a sol–gel precursor in a hydrophobic solution: A potential new route to hybrid molecular imprinted polymers

“…The separation of amino acids, peptides, proteins [10] and steroids [11] have been described using these materials. Chiral separations are a key area of application for these materials [12][13][14].…”