Preparation And Chromatographic Evaluation Of Derivatized Cyclodextrin And Cucurbituril Stationary Phases

With the continuous development of science and technology,chiral problems are increasingly highly concerned.Chiral drugs and chiral pesticides have been widely used,posing new challenges to traditional drug safety and food safety,where the analysis of enantiomers will become a very meaningful,but the separation is facing a very difficult problem.Therefore,the development of new chiral separation materials and technology,and the establishment of enantiomers of the rapid separation of new methods,are the key step to solve the problem.High performance liquid chromatography(HPLC)has the advantages of convenient operation,high efficiency,wide surface separation,mild condition,compatibility of drugs and technology maturity.It has been developed into one of the main methods for the separation and determination of chiral enantiomers.Chiral stationary phase(CSP)method is the most effective method for the separation of enantiomers of chiral drugs because of its good selectivity,applicability and reproducibility.In this paper,we focus on the preparation,evaluation,mechanism and separation of the novel supramolecular derivatized cyclodextrin and cucurbituril-bonded stationary phase,including the following aspects:The first chapter summarizes the new problems associated with the extensive use of chiral drugs and pesticides,and points out the importance of enantiomeric analysis.This paper summarizes the current HPLC methods for the separation of enantiomers of chiral drugs,focusing on the chiral separation principle of chromatography and some commonly used chiral separation materials and their performance comparisons.As the starting point and theoretical basis of this research work.In the second chapter,a mono-substituted p-nitrophenyl ureido-?-cyclodextrinbonded SBA-15 stationary phase(NCDSP)was prepared by the reaction of amino-?-cyclodextrin with active isocyanate-based coupling agent.The structures and morphology of the ligands and immobilized bond phases were characterized by IR,solid-state NMR and TEM.The chiral separation performance was evaluated by using10 kinds of triazole chiral pesticides as the solute and using water and methanol or acetonitrile as mobile phase.The results showed that the new stationary phase had higher selectivity for the triazole chiral pesticide enantiomers,among which the four kinds of triazole fungicides were the best,and the analysis time was as short as 20 min.The resolution of hexaconazole enantiomers reached 2.87,and the peak shape was symmetrical.It was found that the NCDSP column had a better chiral separation effect when the chiral carbon atom was associated with –OH group in the pesticide structure,and the separation ability was poor when the C=O was connected.It is possible that the hydroxyl group on the chiral carbon could form hydrogen bonding with the ligands on the stationary phase,so that the chiral centers of the separated solutes are closer to the ligand recognition groups with a strong three-point effect,thus the enatiomers were separated.The ligand with the modified ureido ports is not only chemical stable but also strong hydrogen-bonding.The introduction of electron-withdrawing nitro group is also beneficial to enhance the interaction and chiral recognition of ligand to basic triazole-based pesticides.In the third chapter,based on the new stationary phase NCDSP as above preparation,the practical analysis application of chiral pesticide enantiomer in food was developed.The similarity of the enantiomers increases the difficulty of chiral separation,and it is necessary to study and optimize the chiral separation conditions,including the composition of mobile phase,the applicable pH value and column temperature,and the calculation of thermodynamic parameters and the turning temperature(Tiso)according to the Van't Hoff equation.The results showed that the chiral separation was controlled by enthalpy,and suitable column temperature should be set to ensure good separation and reproducibility.Four kinds of fruits and vegetables,such as cucumber apple and so on,were used as samples.In addition,the pretreatment method of magnetic recovery samples was also improved.A new HPLC-MS method for the simultaneous determination of three triazole chiral pesticides including fflutriafol,diniconazole and triticonazole was established by highly selective and sensitive mass spectrometry.The linear ranges were wide(0.25~5.00 mg/L).The recoveries were high(85.4~94.60%)with the good reproducibility(RSD 3.24~7.92%,n=5),low LOD(<0.041 mg/L)and low QOD(<0.137 mg/L).Better separations of six enantiomers were acheved within 30 min,saving time and testing cost.Therefore,the proposed method has a good application prospectsgood in food and drug analysis.In the fourth chapter,a bridged bis-6-monoamino-?-cyclodextrin-bonded phase(DCDSP)was prepared because bis-cyclicdextrin molecule has the excellent property in molecular recognition and artificial mimetic enzyme.However,its separation function,the current relevant chromatography application remains to be exploited.The chiral chromatographic properties of DCDSP were evaluated by using triazole chiral fungicides,hydroxyflavanones,?-blockers as probes.The results showed that the enantiomeric separations of tebuconazole and hexaconazole were 1.63 and 1.58.The resolution of 2'-hydroxyflavanone was 2.14,and the resolution of metoprolol and atenolol was 1.35 and 1.32,respectively.Obviously,the separation ability of DCDSP on the solutes is stronger than that of CDSP,which may be synergistic with the two cavities of bridged cyclodextrin.In addition,the bridging cyclodextrin site more,three-point effect is more obvious.In the fifth chapter,cucurbiturils is a new supramolecular compound,which is different from the inclusion complex of cyclodextrin.It has a strong association ability and recognition of polar molecules.In this paper,we first prepared a cucurbituril-substituted ?-cyclodextrin stationary phase,which combines the properties of two supramolecular compounds to provide a richer site for neutral and ionized solutes.The study found that the column can be used for a variety of separation modes.For example,by with 5% methanol aqueous solution it could separate benzene homologues and polycyclic aromatic hydrocarbons,although the polarity of ligand is strong,it can still be used for reversed-phase chromatography,saving greatly in organic solvents.The separation of nitroaniline and other groups of positional isomers were also acheved,showing excellent position selectivity.At the same time,the new column remains a good chiral separation ability for hexaconazole and 2'-hydroxy flavanone enantiomers.This stationary phase with synergistic supramolecular ligands has a special separation function,but its chromatographic performance still needs further study.