Separation And Purification Of Lactic Acid From Zymotic Fluid With Ion-exclusion Chromatogram

Lactic acid which is classified to be L-lactic acid, D-lactic acid and DL-lactic acid according to its configuration and optical activity is one kind of organic acids. Polylactic acid the polymer of L-lactic acid is one kind of green macromolecule materials. It is deemed to be the most promising new material in the new century because of its good degradability in the nature. The most part of homemade lactic acid is DL-lactic acid. There is little domestic plant which can produce L-lactic acid with high quality. My research cooperated with Henan Jindan lactic acid corporation and studied on the separation of lactic acid and glucose in the L-lactic acid producing post procedure.Ion-exclusion chromatogram (IEC) was adopted to separate the lactic acid and the glucose in the research. The stationary phase of ion-exclusion chromatogram mainly rely on importation in the domestic market at present. Synthesizing the IEC stationary phase in the research would be a maiden attempt. The monomer MMA was added in the copolymerization of St and DVB. The sulfonic groups were brought in through sulfonation and the carboxylic groups were bought in through hydrolization.The main part of stationary phase is the St/MMA/DVB cross-linked copolymer. The lifespan of resins will be decreased if the cross-linking structure of copolymer is uneven. It was studied on MMA-DVB-St copolymerization systems by gas chromatography. The result shows that the reaction rate of St and DVB is accelerated by MMA. And the acceleration of MMA towards St is larger than that towards DVB. The uneven cross-linking of polystyrene resins is obviously improved by increasing the concentration of MMA. But the difference of reaction rate between DVB and St, MMA is climbing by increasing the concentration of DVB. That is, the uneven cross-linking of resins will be worsen in the highly cross-linked system.Secondary, it was studied on the quantification control of multiple functional groups of stationary phase. It is found that the extent of sulfonation is similar when the resins are sulfonated with the same concentration of sulfuric acid, and the extent of hydrolization inclines to a invariable value when the concentration of NaOH is more than 20%. The principle how to bring in tow kinds of groups quantitatively was concluded. 95% sulfuric acid should be used as sulfonating agent when the material ratio of St and MMA is 1.88X. 85% sulfuric acid should be used as sulfonating agent when the material ratio of St and MMA is 2.04X (X is the ratio of the sulfonic groups and the carboxylic groups of the stationary phase). Third , the separation procedure of lactic acid and glucose was studied. The resolution of lactic acid and glucose is firstly increased and then decreased when contention of the carbocylic acid groups of the stationary phase is increased. The resolution is bigger than 1.5 when the contention of the carboxylic groups is less than 30%. In that situation, the lactic acid and glucose are totally separated. The stationary phase with bigger pore volume is propitious to the separation of the two compounds. Considering the environmental protection, water is adopted as the mobile phase, although separation effect is better with hydrochloric acid as mobile phase. There is little influence of column temperature on the separation of the two compounds. 30℃is chosen as the column temperature, because low temperature is helpful to the lifespan.of resins.