CEC enantioseparations of carboxylic acids on silica‐based monoliths modified with ergot alkaloid derivative

Abstract

The enantioseparation of carboxylic acids, including amino acid dansyl-derivatives, 2-arylpropionic acids and 2-aryloxypropionic acids, was tested by CEC on a porous silica sol-gel monolithic column that was prepared by polycondensation of tetramethoxysilane in acidic conditions and post-gelation heat treatment (120 degrees C for 3 h) in the presence of urea, and successively, by anchoring to the silica (+)-1-allyl-(5R,8S,10R)-terguride as the chiral selector. The bimodal structure of the sorbent showed through pores with a median value of 1.39 mum and a mesopore size distribution ranging between 6 and 12 nm (average pore size of 9.9 nm). To attain optimum separation conditions, the influence of the pH and the concentration of the buffer solution in the mobile phase on resolution were investigated. The monolithic column showed: (i) for the compounds studied resolution values two or three times higher in comparison with previously developed separation systems where the same chiral selector was used. For example, on the monolithic column Dns-serine enantiomers were much better separated (8 min with a selectivity factor of 1.34) than by HPLC (20 min, alpha=1.17); (ii) high chemical and mechanical stability as demonstrated by the use of such column for hundreds of analysis along about 1 year without significant variations of the resolution and the retention parameters.

Advances in enantiomeric resolution on monolithic chiral stationary phases in liquid chromatography and electrochromatography

“…The reverse order of elution on different CSPs may be useful to determine the mechanisms of chiral recognition. Messina et al [128] prepared a (+)-1allyl-(5R,8S,10R)-terguride-based monolith CSP for CEC. The CSP was prepared by polycondensation of TMOS in acidic solution followed by postgelation heat treatment (120ЊC for 3 h) in the presence of urea and the chiral selector.…”

“…Messina et al. prepared a (+)‐1‐allyl‐(5 R ,8 S ,10 R )‐terguride‐based monolith CSP for CEC. The CSP was prepared by polycondensation of TMOS in acidic solution followed by postgelation heat treatment (120°C for 3 h) in the presence of urea and the chiral selector.…”

Recent progress in capillary electrophoretic analysis of amino acid enantiomers

“…In the chiral M-CEC separation of amino acids with silica-based monolith, ␥-CD [137], (+)-1-allyl-(5R,8S,10R)-terguride [138] and maleopimaric acid-bonded, and silica particles binding teicoplaninaglyconeloaded silica monoliths [139] have been employed. On the other hand, acrylate monolithic capillaries have been also applied to CEC with binding several CSs such as QN derivative [140], l-4-hydroxy-Pro [141],␤-CD derivatives [142] and maleopimaric acid [143].…”

Enantioselective capillary electrochromatography: Recent developments and new trends

“…This is a demonstration of the application of CEC to real samples, which is often missing in the developed applications. A silica monolithic backbone was tested also in combination with an (5R,8S,10R)-terguride derivative [70]. Superior resolving capacity of this type of monolithic backbone was found, with fourfold Rs increase for some separations compared with the methacrylate-based monolith.…”