A Study Of The Star-Shaped Molecularly Imprinted Coating And Boronate Affinity Molecularly Imprinted Monolith

With a mixture of S-amlodipine(S-AML)as the template,Ov-POSS as the cross-linker,and methacrylic acid(MAA)as the functional monomer,the star-shaped molecularly imprinted capillary coating column was successfully prepared by in situ polymerization and achieved the chiral separation of amlodipine(AML)isomers in capillary electrochromatography(CEC)mode.In order to obtain a better separation effect,the effect of synthesis conditions and chromatographic separation conditions were investigated,including the ratio of template molecule to functional monomer,the content of cross-linker,and the pH value,acetonitrile content,salt concentration of the mobile phase.The coating column prepared by using Ov-POSS as a cross-linking agent has good recognition ability for template molecule.The best resolution of AML enantiomers was up to 33.0,the selectivity factor was 2.60,and the column efficiency of S-AML was 54,000 plates/m.Even if the content of the cross-linking agent was as low as 9.1%,chiral separation of racemic amlodipine can also be achieved.In addition,the column capacity of the coating column containing Ov-POSS was 10 times that of coating column without Ov-POSS,and the detection sensitivity was also significantly improved.At the same time,Ov-POSS-based MIP coating column with d-zopiclone and R-ketoprofen as template molecule were also prepared and chiral separation can also be achieved.The experimental results showed that Ov-POSS can be used as the core of the polymer and form the star-shaped molecularly imprinted polymer with the relatively open three-dimensional structure by mediating the chain-chain interaction.The polymer has good site accessibility,which made the template molecule elute and recombine with the polymer matrix easily,and the number of active imprinting sites increased.Such strategy can solve the problem of excessively embedded of imprinting sites under traditional conditions.Therefore,Ov-POSS was an effective cross-linking agent for the preparation of MIPs,which can increase the column capacity,improve the separation effect,and enhance the accessibility of the imprinting sites.In this study,the boronate affinity polymer backbone was firstly prepared by in situ polymerization using 4-vinylbenzeneboronic acid(VPBA)as functional monomer,pentaerythritol triacrylate(PETA)as cross-linking agent,and a mixture of ethylene glycol,cyclohexanol,tetrahydrofuran,and polyethylene glycol(PEG)as a novel quaternary porogen.Then,the template molecule catechol was combined with the polymer backbone,and dopamine(DA)was self-polymerized and deposited on the polymer skeleton surface under alkaline conditions.After removing the template,the boronate affinity catechol-imprinted monolithic column can be obtained and used for the solid phase microextraction(SPME)of catechol.The combination of boronate affinity and surface molecular imprinting technology can enhance recognition ability of target cis-dihydroxyl molecules.In addition,surface imprinting technology can greatly avoid excessively embedded of the imprinting site,thereby improving the extraction efficiency and specific selectivity.PEG is a linear macromolecule porogen,which can control the pore structure of the monolith,so the monolith with better permeability,high mechanical strength and larger surface area can be obtained.The effects of synthesis conditions and SPME conditions on the recovery of catechol were investigated,including the content of VPBA,the molecular weight and content of PEG,the sample solution pH,the sample concentration,the eluent volume and the ratio of acetic acid(HAc)to ACN in the eluent solvent.Under the optimal conditions,the catechol-imprinted monolith has good column permeability and mechanical stability.Meanwhile,it also showed the strong recognition ability of catechol and the recovery can reach 97%.In addition,the catechol-imprinted monolith had the application value for real sample and the recovery of catechol in water samples were in the range of 83.4-94.3% with RSD less than 4%.The results showed that this method can be applied to the specific separation and enrichment of catechol.