Chiral separation of aryloxyphenoxy‐propionate herbicides in a permethyl‐β‐cyclodextrin based column. Influence of temperature and mobile phase composition on enantioselectivity

Abstract

We used a permethyl-β-cyclodextrin chiral stationary phase under reversed-phase conditions for the chiral separation of four aryloxyphenoxy-propionate herbicides (fenoxaprop-p-ethyl, quizalofop-p-ethyl and tefuryl, and haloxyfop-p-methyl) with mixtures of methanol, ethanol, 2-propanol, n-propanol, tert-butanol, or acetonitrile and water as mobile phases and investigated the influence of mobile phase composition and column temperature (from 0 to 50°C) on the separation. The retention factors (k) and selectivity factors (α) of all the herbicides investigated decreased with increasing temperature. The lnα versus 1/T and lnk versus 1/T plots for the enantiomers of the chiral pesticides were linear within the range of 0-50°C with all alcohol/water mixtures constituting the mobile phase, but the lnk versus 1/T plots were nonlinear for all the enantiomers chromatographed in acetonitrile/water mixtures. The thermodynamic parameters based on linear van't Hoff plots were calculated. The influence of temperature and mobile phase composition on the enantioseparation of the solutes has rarely been considered simultaneously. The temperature and the solvents used in the mobile phase, however, were found to have a profound effect on the enantioseparation of these herbicides.

Efficient preparative separation of 6‐(4‐aminophenyl)‐5‐methyl‐4, 5‐dihydro‐3(2H)‐pyridazinone enantiomers on polysaccharide‐based stationary phases in polar organic solvent chromatography and supercritical fluid chromatography

“…Temperature is of great importance both for the optimization of enantioseparation and the elucidation of the enantiorecognition mechanisms . To eliminate the phase ratio influence, modified van't Hoff equation was undertaken to investigate the chiral discrimination process of the two enantiomers : Where R is the universal gas constant (8.314 J/ (mol K)), T is the absolute temperature.…”

A new single‐urea‐bound 3,5‐dimethylphenylcarbamoylated β‐cyclodextrin chiral stationary phase and its enhanced separation performance in normal‐phase liquid chromatography

“…Nature and composition of the mobile phase usually play crucial roles in chromatographic separations. Organic modifiers and acidic/basic additives might significantly enhance eluting ability of mobile phases, leading to fast and satisfactory enantioseparation of chiral compounds . Effects of alcoholic modifier and acidic/basic additive on enantiorecognition of the SDMP in the normal phase mode HPLC were studied in this work.…”

“…The alcohol molecules in the mobile phase have strong tendency to form hydrogen bonds with ‐NHCO‐ groups on the rim of the cyclodextrin cavity and occupy active sites favorable for chiral discrimination. In addition, it is assumed that the lower‐polar alcohol affords weaker solvation of analyte molecules, and this might enhance interactions with the CSP .…”

State-of-the-art and recent developments of immobilized polysaccharide-based chiral stationary phases for enantioseparations by high-performance liquid chromatography (2013–2017)

“…Several studies using different CSPs [40,53,[145][146][147][148][149][150] demonstrated that the column temperature should be optimized in enantioselective HPLC separations.…”