| Capillary electrophoresis has been paid more and more attention because of its advantages such as low sample amount,fast separation speed,high sensitivity,high sensitivity,easy operation and low cost.Many researchers put into the study of this technology,so that the technology matures,and promote the application to more and more fields.It has many separate mode,including electrokinetic chromatography,micellar electrokinetic capillary chromatography,microemulsion electrokinetic chromatography and capillary electrochromatography,which increased the capillary electrophoresis method in the application of flexibility.In recent years,with the development of capillary coating technology,the application of capillary electrophoresis in the separation and detection of chiral drugs has become one of the hot spots.The nature of matter determines its application.The insoluble organic acid due to the solubility in water is very small,the ionization constant unpredictable.Because the isomerism of organic matter is very common,we often need the help of the physical properties of the analytical instrument to realize the separation of isomers,such as the use of the different ionization constants by pH potentiometric titration,UV and electrochemical workstation to achieve its separation.This paper mainly discusses the coated capillary electrophoresis diodearray detector technique for chiral separation of citalopram and determine the optimal separation conditions and pH titration method for the determination of insoluble organic acid xylenol isomers of three of the ionization constant method of preliminary exploration.Because of the similarity of the structure and properties of the two enantiomers of chiral drugs,the separation of the two drugs is very difficult.IIn view of the two different opticity,we use synthetic capillary coating technology of chiral column so as to realize the two kinds of citalopram enantiomers separation.Optimal experimental conditions for the separation of citalopram : Determine the running buffer of pH = 5.40,the concentration of 15 mmol·L-1 six-HCl four methylene amine buffer;the separation voltage of 30 kV;the temperature is 25 DEGC,the detection wavelength of 240.0nm,the sample solution was injected in the hydrodynamic?3.43×103 Pa?for 10 s mode.The linear range was 0.03-0.20mmol·L-1,the detection limit was 0.022 mmol·L-1,and the relative standard deviation was less than 0.45%.The degree of separation was 4.25.Experimental study on Determination of ionization constants of different isomers of xylenol by pH acid-base titration.We first explored the dissolution conditions of dimethlbenzene,and determined the operating conditions required for dissolution reagent and dissolution.Then,a solvent with gradient concentration was used to dissolve xylenol,and the xylenesolution was obtained.Next,xylenol solution was titrated with sodium hydroxide solution,and the p H value of the solution was measured with a pH meter at regular intervals.Finally,the data are processed by Origin8.0software to get the experimental results.The effect of solvent ratio and temperature on solubility of xylenol was investigated in the dissolution experiment.The experimental conditions for measuring the ionization constant of xylenol have been preliminarily explored by pH titration method.The ionization constants of 2,4-xylenol,2,5-xylenol,3,5-xylenol in alcohol/water mixed solvent?different volume ratio?were detminated. |
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