Preparation And Retention Behavior Of Light-induced Polarity Controllable Stationary Phase

As a powerful tool,chromatography is widely used in the fields of environment,food and petroleum.For the stationary phase as the core of chromatography,many kinds of stationary phases have been developed so far,but these stationary phases are still unsatisfactory for the separation of complex polar samples due to some chemical and mechanical limitations.Multi-dimensional chromatography with a series of chromatographic columns in series has played a huge advantage in the separation of complex samples,however,this inevitably makes the chromatographic instruments complicated and bulky.Therefore,some scholars put forward the concept of"responsive stationary phase",that is,the properties of the stationary phase inside the chromatography are changed by external stimuli.Among them,temperature-and p H-responsive materials have been successfully applied in chromatographic protein purification,cell separation,etc.Compared with the above two responsive materials,light-responsive materials have great advantages in spatiotemporal flexibility.At present,photosensitive materials represented by azobenzene have been widely used in optical materials,drug delivery and other fields due to their light-induced reversible cis-trans configuration,accompanied by changes in molecular size and polarity.To sum up,in this paper,the photosensitive material azobenzene is used as the stationary phase of gas chromatography,and the property of photosensitive polarity enhancement is introduced into the gas chromatography column.The problem of stationary phase refinement and separation of complex samples and miniaturization of multi-dimensional chromatography.The specific research contents are as follows:Inthispaper,theazobenzenederivativemolecule4-[3-(triethoxysilyl)-propoxy]azobenzene was synthesized,and the photo-responsive capillary gas chromatography column was prepared by dynamic coating method.Taking sample with different polar ranges(alkanes,benzene,and alcohols)as examples,the changes in the retention behavior of sample before and after light induction were explored.And it can be restored to the original state at 473 nm,indicating that the photo-responsive capillary column light response regulation of chromatographic separation has certain feasibility.Then,the changes of polarity and partition coefficient of azobenzene photosensitive stationary phase were evaluated by Mc Reynolds constant and thermodynamic constant.The average polarity of Mc Reynolds constant indicates that the photo-responsive stationary phase is weakly polar and the polarity is enhanced before and after light induction at 365 nm.The changes in molar enthalpy of solution,molar entropy of solution and Gibbs free energy demonstrate the change in the partitioning properties of the stationary phase before and after light induction.Furthermore,by changing the photoinduction time,the correlation between the sample retention factor and the cis-trans configuration ratio was explored.The results showed that the ratio of cis-trans isomer molecules had a good linear relationship with the sample retention factor(R~2=0.9859),which proves the fine-tuning theory of photosensitive chromatography that can use the illumination time to control the cis-trans isomer ratio of the stationary phase and then control the polarity of the macro-stationary phase.Finally,the multidimensional chromatographic separation in the time dimension of the photosensitive capillary chromatographic column was explored by intervening diverse light-induced modes in the separation process.The feasibility of two-dimensional photo-responsive chromatography was proved by comparing the retention time changes of n-butanol in mixed alcohol samples under no light conditions and after being induced by light at 365 nm.The feasibility of multi-dimensional photo-responsive chromatography was demonstrated by comparing the retention time changes of the same samples induced by single light at365 nm and mixed light at 365 nm and 473 nm.This paper is of great significance for enriching the types of chromatographic stationary phases,developing new chromatographic separation techniques,and solving the problems of complex switching valves and difficult integration of multi-dimensional liquid chromatography on a chip.Providing a research basis for latter.