Separation Of Phenylalanine And Aspartic Acid In Aspartame Mother Liquor

There are two kinds of amino acids (phenylalanine and aspartic acid) existing in the aspartame mother liquor, phenylalanine couldn't be reclaimed by the routine separation methods, which is very expensive in the market. Chromatographic separation method was selected in the separation process of phenylalanine and aspartic acid which could separate them from each other. The results of this thesis were listed as follow:1. Compared with the other examination methods, the double-wavelength ultraviolet examination was applied, which the concentration of this two amino acids can be easily and extremely accurate quantified at the wavelength 257nm and 230nm. It also calculated the standard deviation of this method when it was applied in industry, The standard deviation of phenylalanine and aspartic acid were less than 1% and 3% respectively.2. The chromatographic separation was selected in this thesis. Several different kinds of representative stationary phase and mobile phase were selected in the separation of phenylalanine and aspartic acid. The result indicated that the adsorption resins were well behaved when water was used as the mobile phase. Then the three important characters of adsorption resins were studied in further at the same chromatographic conditions. It was revealed that polarity of the adsorption resins was the key ingredient in the whole process. Phenylalanine and aspartic acid could be effective separated on the non-polar and weak-polar resins, the separation degree on AB-8 can reach to 6.887.The retention time order of phenylalanine on adsorption resins were as follow: weak-polarity>non-polarity>middle-polarity>polarity resins; the retention time of aspartic acid were increased with the polarity increase, and it also increased with the prove volume increase, but not for the surface area change on the weak-polarity adsorption resins. The retention time of phenylalanine were fluctuated in a small range with the change of surface area and prove volume of weak-polarity adsorption resins3. There were two kinds of acting force existing in the adsorption process, hydrophobic interaction and hydrogen bonding interaction, while only hydrogen bonding interaction existed in the adsorption of aspartic acid on Ab-8 resin. The hydrogen bonding played a predominant role in the separation process, and the hydrophobic interaction would shorten the distance between the two hydrophobic groups of AB-8 resin and phenylalanine, which would strengthen the hydrogen bonding interaction consequently in water. The hydrogen bonding interaction would be strengthened by adding some salt in water. Because the surface tension of the water could be decreased, which weaken the protection of the hydrophobic groups by water and promoted to the integration of the hydrophobic groups.When the ion strength contunine to decrease, the result indicated that the retention time of phenylalanine increased in linear with the ionic strength, and it also revealed that the strengthen of the hydrogen bonding interaction didn't appear until conquer a fixed value, then it will complete instantaneously.4. The value of the total and external voidage were 0.790 and 0.310 respectively, which were investigated by radiotracer method. The adsorption isotherm of phenylalanine and aspartic acids were investaigated by the frontal analysis. Then the adsorption behavior of phenylalanine was studied when aspartic acids existing in the mixture, it was indicated that there were two adsorption points on AB-8 resin, and there was no competition between phenylalanine and aspartic acids on AB-8 resin.