Study On Influence Factors On Mixed Catanionic Surfactants Vesicles As Pseudostationary Phase

The vesicles formed by mixing cationic surfactant and anionic surfactant?catanionic surfactants?have high stability,and are suitable to be used as pseudostationary phase in electrokinetic chromatography?EKC?,owing to many advantages such as wide migration window and high selectivity.In our previous wrk,it was found that the vesicle formed from mixedoctyltriethylammoniumbromide?C₈NE3Br?andsodiumdodecylbenzene sulfonate?SDBS?system spontaneously.C₈NE₃Br/SDBS system,none turbidity phenomena appeared while mixing catanionic surfactants at any molar ratio,had been developed as pseudostationary phase in EKC to separate eight corticosteroids.On the basis of previous research,the further researches on influence factors on mixed catanionicsurfactants vesicles as pseudostationary phase were carried out in the thesis.The main research contents and results were as follows:1.The factors on the formation of vesicles,the effects of the surfactant concentration,the molar ratio of cationic to anionic surfactant,temperature,organic solvents,pH and ionic strength on the vesicle properties were investigated.The experimental results showed that the molar ratio of C₈NE₃Br to SDBS ranged from 2:8 to 8:2,and the concentration of the total surfactant concentration changed from 5 to 80 mmol/L,all of the mixed C₈NE₃Br/SDBS systems formed vesicles spontaneously,which were testified by TEM.The molar ratio of C₈NE₃Br to SDBS,the total concentration of surfactants,and organic solvent content could directly change the size,surface charge density and micro-environmental polarity of the vesicles.The vesicle system were more stable at the temperature between 20°C and 40°C and at pH 7.0¹0.0.As NaCl concentration in the vesicle system increased from 0 to 120 mmol/L,vesicle size did not change,but the absolute value of Zeta potential decreased firstly and then stayed almost the same,therefore,ionic strength had little effect upon vesicle system.In the C₈NE₃Br/SDBS vesicle system,the size of vesicles increased with the increase of organic solvent content,and the Zeta potential decreased.When the molar ratio of the anionic and cationic surfactants is near to 1:1,the formed vesicles could tolerate higher content of organic solvents,and the highest tolerance were 20%?v/v?methanol,10%?v/v?acetonitrile,and 6%?v/v?butyl alcohol.2.The C₈NE₃Br/SDBS system had been developed as pseudostationary phase in EKC,we investigated the performances and separation mechanism of vesicles PSP in EKC.With the increase of surfactant concentration,methylene selectivity for all vesicle PSPs including the molar ratio of 3:7,4:6,5:5 and 6:4 increased.With the increase of catanionic surfactants concentration,migration window of vesicle PSPs had different tendencies at different molar ratio of C₈NE₃Br to SDBS.The total surfactant concentration increased,migration window broadened at the molar ratio of C₈NE₃Br to SDBS of 3:7.Unexpectedly,migration window became narrowed at molar ratio of 5:5 and 6:4,elution window increased firstly then decreased at molar ratio of 4:6.Fixed the total surfactant concentration at 20 mmol/L,the methylene selectivity of the vesicle PSP for molar ratio of 5:5 and 3:7 were better and comparable,but migration time of vesicle PSP at molar ratio of 5:5 shortened by a half.Fixed the total surfactant concentration at 20 mmol/L,elution orders of 12 kinds of substituted benzene substances were different using vesicle PSP at molar ratio of 3:7 and 5:5,which indicated that they had different separation mechanisms.The former had a little better selectivity than the latter,and both PSP had good functional group selectivity.Fixed the total surfactant concentration at 20 mmol/L,we investigated the separation mechanism of vesicle PSPs at molar ratio of 3:7 and 5:5,LSER model analysis result showed that the hydrophobic interaction between vesicle PSP and the solutes,the hydrogen bond acidity of the vesicle PSPs had the most influences on the PSP separation process.3.The vesicle PSPs were applied to separate 12 kinds of dyes intermediates under different conditions,to find out the optimal condition.The vesicle PSP was successfully applied to the analysis of 12 kinds of dyes intermediates in the hair dye products with EKC.The molar ratio of C₈NE₃Br to SDBS,the total surfactant concentration,pH of the running buffer,separation temperature had significant influences on separation performances for 12kinds of dye intermediates with EKC,under the optimal condition,the 12 kinds of dye intermediates could be separated completely within 10.5 min.