Imprinted Monolithic Column And Solvent Extraction Applied Research, In The Chiral Separation

Chrial separations of DBTA and Ofloxacin enantiomers were investigated using molecular imprinting technique and solvent extraction respectively.(1) The Dibenzoyl-D-tartaric acid (D-DBTA) monolithic molecularly imprinted polymer (MIP) was prepared by in situ polymerization using D-DBTA as the template, Acrylamide(AM) as the functional monomer, Ethylene glycol dimethacrylate(EGDMA) as the crosslinker, and lower polar solvents (toluene and dodecanol) as the porogenic solvents. With the optimization of polymeric and chromatographic conditions, the enantioseperation of DBTA was succussfully achieved within 25 min on the obtained MIP with a resolution factor Rs=1.25, whereas no enantioseparation effect of DBTA was acquired on the monolithic non-imprinted polymer (NIP). Thermodynamic data of separation were calculated. The results revealed that two different thermodynamic processes existed within temperature investigated and both fitted Van't Hoff plot very well. Just at transition temperature of the two thermodynamic processes, the maximum of separation factor a appeared. Scathcard analysis indicated that only one class of binding sites existed in the obtained MIP, with its Kd and Qmax estimated to be 5.457×10-4 mol/L and 229.6μmol/g, respectively. Nitrogen adsorption experiment proved that the prepared MIP had a large specific surface area of 105 m2/g. Scanning electron microscopy showed that large flow-through pores were present on the prepared monolith, as a consequence, the backpressure was only 1.2 MPa at the flow rate of 1.0 mL/min using acetonitrile as the mobile phase.(2) The D-DBTA monolithic molecularly imprinted polymer (MIP) was prepared by reversible addition-fragmentation chain transfer(RAFT) process using D-DBTA as the template, AM as the functional monomer, EGDMA as the crosslinker, dibenzyltrithiocarbonate (DBTTC) as the RAFT agent. The differences between D-DBTA MIPs prepared by the RAFT process and the traditional polymerization process were compared. It turned out that the D-DBTA MIP prepared by RAFT process had a relatively narrow range of pore size distribution, and had a better binding property to D-DBTA molecules. When used in chromatographic separation of DBTA enantiomers, it can improve the column efficiency and reduce separation time.(3) The distribution behavior of Ofloxacin (OFLX) enantiomers was examined in a two-phase aqueous-organic solvent mixture containing D2EHPA and tartaric acid derivatives(L-DBTA and L-DTTA)as the mixed complex chiral selector. The influence of composition of the mixed complex chiral selector, initial concentration of OFLX, pH of aqueous phase and temperature was investigated. The results showed that a maximum enantioselectivity of 2.43 was obtained when the molar concentration ratio of L-DBTA to L-DTTA is 2:3(L-DTTA concentration 0.18 mol/L, L-DBTA concentration 0.12 mol/L) and the pH of aqueous phase is 6.86 at 25℃, with DD and DL up to a relative high value of 10.2 and 4.20, respectively.