Application And Research Of SPE Monolithic Column-pCEC In Separation And Detection Of Polyphenols In Sugarcane

Polyphenols are ubiquitous in the plant kingdom,with antioxidant,anti-inflammatory,anti-allergic,antibacterial,heart protection and other physiological functions.Because of their high utilization value and wide distribution in nature,they have attracted More and more researchers are paying attention.Sugarcane leaves,cane tips,and cane stems all contain polyphenols.A few of them are in free form in sugarcane,and most are combined with cellulose,protein,lignin,flavonoids,sugar groups,and organic acids.It exists in the primary and secondary walls of plant tissues,which increases the difficulty of extraction and separation of polyphenols.Solid-phase extraction technology（SPE）,as a commonly used sample pretreatment technology,is often combined with chromatographic analysis for the separation and analysis of substances to be tested in complex systems,which simplifies the sample pretreatment process and improves the detection sensitivity.As a new technology emerging in recent years,the monolithic column has broad application prospects as a solid phase extraction column for sample preparation because of its advantages of simple preparation,good stability,loose porosity,and low cost.In this paper,different monomers are used to prepare a variety of monolithic columns by in-situ polymerization,and they are used as SPE columns for sample pretreatment of polyphenols in sugarcane,and are combined with pressurized capillary electrochromatography（p CEC）to separate and measure the sample,the effect and general rule of SPE monolithic columns obtained with different monomers on the extraction process of polyphenols in sugarcane were investigated.On this basis,using butyl methacrylate（BMA）as the monomer and doping metal-organic framework materials（MOFs）,a MIL-53（Al）-polymer monolithic column was prepared,which increased the specific surface area of the monolithic column,increase the enrichment factor of polyphenols in sugarcane,improve the detection sensitivity,and simplify the sample pretreatment process.The main research contents and results are as follows:1.Established the p CEC method for the separation and determination of three polyphenols in sugarcane:chlorogenic acid,ferulic acid,and epicatechin.The experiment investigated the chromatographic conditions such as mobile phase ratio,buffer salt p H,buffer salt concentration,separation voltage and flow rate.Under optimal chromatographic conditions[mobile phase:15.0 mmol/L Na H₂PO₄+12.5 mmol/L sodium heptane sulfonate（p H 5.0）/methanol（50:50,V/V）;total flow rate of mobile phase:0.06 m L/ min;separation voltage: 1 k V;detection wavelength 220 nm],chlorogenic acid,ferulic acid,and epicatechin have a good linear relationship,with correlation coefficients（r）of 0.9978,0.9922,and 0.9971,and average recovery rates of 96.79%,100.71%,and 99.01%,respectively.Three polyphenols in sugarcane were separated and tested.2.Using acrylamide（AM）as the monomer,polyacrylamide-ethylene glycol dimethacrylate（poly（AM-co-EDMA））monolithic column was synthesized in a polypropylene material syringe by in-situ polymerization.It was characterized by infrared spectrometer（FT-IR）and scanning electron microscope（SEM）,which showed that poly（AM-co-EDMA）monolithic column had good polymerization effect and stable internal structure.At the same time,the factors affecting the performance of the monolithic column were studied,and the various conditions when the SPE monolithic column was used for the SPE of polyphenols in sugarcane were optimized,and the poly（AM-co-EDMA）-p CEC combination method was established for separating and measuring polyphenols in sugarcane.The results show that the method is simple and has high sensitivity for sample pretreatment.The average recoveries of chlorogenic acid and ferulic acid are 99.43%and 98.51%,respectively,and the results are satisfactory.3.Using vinylpyrrolidone（NVP）,styrene（ST）,p-vinylphenylboronic acid（VPBA）and butyl methacrylate（BMA）as monomers,a series of monolithic columns with different polarities were synthesized in situ,each monolithic column was used as an SPE column to explore the general rule of extracting polyphenols from sugarcane with monolithic SPE monolithic columns of different polarities.Each monolithic column was characterized by infrared spectrometer（FT-IR）,scanning electron microscope（SEM）,micropore physical chemical adsorption（BET）,and at the same time,the factors affecting the overall column performance were studied.The poly（VPBA-co-EDMA）monolithic column was chosen as the optimal monolithic column.The experiment optimized the various influencing factors when using the SPE monolithic column for SPE,and established a poly（VPBA-co-EDMA）-p CEC combined separation and determination method for polyphenols in sugarcane.Sample preparation in this method is simple,and the average recovery rates of chlorogenic acid and ferulic acid are 99.87%and 100.71%,respectively.4.Using butyl methacrylate（BMA）as the monomer,add MIL-53（Al）MOFs material to the overall column prepolymerization solution,MIL-53（Al）-polymer monolithic columns doped with MIL-53（Al）MOFs were synthesized by in-situ polymerization.It was characterized by infrared spectroscopy（FT-IR）,scanning electron microscope（SEM）,microporous physical chemical adsorption（BET）,and X-ray diffractometer（XRD）.At the same time,the effect of the amount of doped MIL-53（Al） material on the extraction performance of the overall column was investigated,and optimize the conditions of this monolithic column for SPE of polyphenols in sugarcane,A method for separation and determination of polyphenols in sugarcane by MIL-53（Al）-polymer-p CEC was established with satisfactory results.