Preparation and application of quinidine functionalized monolithic columns for chiral separation by micro-hplc
- Autores: Qiqin Wang
- Directores de la Tesis: María Luisa Marina Alegre (dir. tes.), Zhengjin Jiang (codir. tes.)
- Lectura: En la Universidad de Alcalá ( España ) en 2016
- Idioma: inglés
- Tribunal Calificador de la Tesis: Shaoping Li (presid.), Zuanguang Chen (secret.), Chunsun Zhang (voc.), Pinghe Yin (voc.), Zong Dai (voc.)
- Materias:
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- Resumen
Conclusions From the results obtained in this doctoral thesis, it can be concluded that:
--A capillary monolithic column containing carbamoylated quinidine as chiral selector was re-optimized in order to obtain satisfactory column permeability, efficiency and selectivity in micro-HPLC. The optimized poly (MQD-co-HEMA-co-EDMA) monolithic column showed excellent morphology, good permeability, reproducibility, mechanical and chemical stability and satisfactory chromatographic performance in micro-HPLC.
--The polymerization mixture consisting of 35 wt% monomers (MQD/HEMA/EDMA, 20/57.5/22.5, w/w/w) and 65 wt% porogens (dodecanol/cyclohexanol, 83.33/16.67, w/w) was chosen for the preparation of poly(MQD-co-HEMA-co-EDMA) monolithic columns.
--The optimized poly(MQD-co-HEMA-co-EDMA) monolithic column was first applied to the enantioseparation of a wide range of N-derivatized amino acids with exceptionally high selectivity values and good resolution, especially for 3,5-DNB-amino acids and 3,5-DClB-amino acids. Good chemoselectivity of the monolithic column for a multicomponent mixture of N-derivatized amino acids was also obtained.
--Based on a comparison of the influence of the type of N-protecting groups and amino acids on enantioseparation, it was deduced that the size and bulkiness of the side chain of amino acids as well as the electrophilic character of the N-protecting groups are likely to affect the enantiodiscrimination potential of the poly(MQD-co-HEMA-co-EDMA) monolithic column.
--A baseline separation of all stereoisomers of 24 out of the 53 small peptide derivatives was also obtained on the poly(MQD-co-HEMA-co-EDMA) monolithic CSP, demonstrating its excellent enantioselectivity and diastereoselectivity.
--The effects of the apparent pH of the mobile phase, the organic solvent content and the buffer concentration on the retention and separation of the stereoisomers of N-derivatized di- and tri-peptides seem to confirm that electrostatic and hydrophobic interactions are both responsible for the retention of these acidic analytes while chiral recognition is more related to other kinds of intermolecular interactions, such as hydrogen binding, -and steric interactions.
--A first analytical methodology for the quantification of L-carnosine in dietary supplements was developed by the poly(MQD-co-HEMA-co-EDMA) monolithic column. The conditions affecting the reaction between DL-carnosine and FMOC chloride, such as the FMOC chloride/ DL-carnosine concentration ratio, the buffer pH and the reaction time were optimized. FMOC-DL-carnosine enantiomers were baseline separated in less than 35 min.
--The application of the developed micro-HPLC/UV methodology enabled to quantify the content of L-carnosine and D-carnosine in three dietary supplements. In all dietary supplements, the concentration of D-carnosine was below the detection limit (6.25 ¿M) of the present method and the amount of L-carnosine was in agreement with the labeled content for all the analyzed products.
In order to obtain better enantioselectivity and diastereoselectivity, novel quinidine functionalized monolithic column was developed. The optimized poly(MBQD-co-HEMA-co-EDMA) monolithic column exhibited excellent morphology, high mechanical stability, good permeability, reproducibility and satisfactory separation efficiency in micro-HPLC.
--Under the selected conditions, all the 47 N-derivatized amino acids, the eight N-derivatized dipeptides and the two herbicides tested were baseline enantioseparated on the poly(MBQD-co-HEMA-co-EDMA) monolithic column.
--A comparison between the poly(MBQD-co-HEMA-co-EDMA) and poly(MQD-co-HEMA-co-EDMA) monoliths clearly indicated that the MBQD monomer with a more bulky tert-butyl carbamate residue on quinidine exhibited much higher enantioselectivity and diastereoselectivity than the MQD monomer bearing a linear alkyl chain at the carbamate group.
