二(2-乙基己基)磷酸萃取L-色氨酸

EXTRACTION OF L-TRYPTOPHANE WITH DI(2-ETHYLHEXYL)PHOSPHORIC ACID

以二 (2 -乙基己基 )磷酸 (D2EHPA) -正辛烷 (体系A)及D2EHPA -正辛醇 +正辛烷 (体系B)萃取L -色氨酸为对象 ,研究了D2EHPA浓度、L -色氨酸初始浓度、稀释剂组成以及pH值对萃取平衡分配系数的影响 .结果表明 ,在实验研究涉及的pH值 (1.0 <pH <5 .0 )范围内分配系数随着pH值的增加而增大 ,但在 3.5 <pH <5区域pH值对分配系数的影响较小 .体系A中同时存在着 1∶1和 2∶1的萃取反应以及萃合物之间彼此聚集的趋势 ,不同pH值下负载有机相的红外谱图分析表明D2EHPA与L -色氨酸形成的萃合物结构与pH值无关 .体系B中也存在着 1∶1和 2∶1的萃取反应 ,但是由于正辛醇改善了萃合物存在的有机相环境 ,萃合物之间不存在彼此聚集的趋势 .结果再次证实了在D2EHPA萃取氨基酸的过程中同时存在着离子交换反应和质子转移反应 。

A series of equilibrium experiments for extracting L-tryptophane with di (2-ethylhexyl) phosphoric acid (D2EHPA) dissolved in n-octane (system A) and mixture of n-octane and n-octanol (system B) were carried out. The effects of L-tryptophane concentration, D2EHPA concentration, n-octanol concentration and pH on extraction distribution ratio were discussed in detail. In system A, in the range of 1.0 < pH < 3.5, the distribution ratio D increases with the increase of pH, but changes slightly in the range of 3.5 < pH < 5.0. The data indicate formation of both (1:1) and (2:1) D2EHPA/L-tryptophane complexes and the complexes tend to cluster together, away from the low-polarity bulk solvent. The infrared spectrogram of organic phase loaded solute illustrates that the pH condition had little effect on the structure of complex. In system B, both (1:1) and (2:1) D2EHPA/L-tryptophane complexes form, but they do not cluster together because of the diluent which improves the polarity of the bulk solvent. The proton-transfer reaction is again demonstrated in the extraction of α-amino acid with D2EHPA. Expressions of the equilibrium distribution ratio were proposed.