TY - JOUR

T1 - Influence of pH value and ionic liquids on the solubility of L-alanine and L-glutamic acid in aqueous solutions at 30 °C

AU - Voges, Matthias

AU - Prikhodko, Igor V.

AU - Prill, Sebastian

AU - Hübner, Martin

AU - Sadowski, Gabriele

AU - Held, Christoph

N1 - Publisher Copyright: © 2016 American Chemical Society.

PY - 2017/1/12

Y1 - 2017/1/12

N2 - The solubility of the amino acids L-alanine and L-glutamic acid and its sodium salt (sodium L-glutamate monohydrate) in aqueous solutions at 30 °C and atmospheric pressure was investigated in the pH range between 3 and 9 and in the presence of the ionic liquids (ILs) 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([bmim][OTf]) and choline dihydrogencitrate ([ch][dhcit]) at pH 7. The solubility of L-alanine and L-glutamic acid in the solutions without IL was measured by UV spectroscopy and with a gravimetrical method. In the presence of an IL HPLC-analysis was applied. The solid phases were characterized using Raman spectroscopy and powder X-ray diffraction to distinguish the amino acids from their salts. While the solubility of L-alanine did not depend on pH within the considered pH range, the solubility of L-glutamic acid strongly increased with increasing pH. Below pH 6.2 the solid phase was characterized to be L-glutamic acid, while sodium L-glutamate monohydrate was found to be the solid at pH higher than 6.2. It could be observed that the solubility of sodium L-glutamate monohydrate was comparatively high, and increased with increasing pH. Upon addition of the ILs under investigation ([bmim][OTf]) and [ch][dhcit]) the solubility of L-alanine and L-glutamic acid was decreased. Original PC-SAFT was applied to predict the solubility of L-alanine and L-glutamic acid (and its sodium salt) in water, with and without the ILs under consideration, at the experimental conditions with quantitative agreement to the experimental data. (Graph Presented).

AB - The solubility of the amino acids L-alanine and L-glutamic acid and its sodium salt (sodium L-glutamate monohydrate) in aqueous solutions at 30 °C and atmospheric pressure was investigated in the pH range between 3 and 9 and in the presence of the ionic liquids (ILs) 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([bmim][OTf]) and choline dihydrogencitrate ([ch][dhcit]) at pH 7. The solubility of L-alanine and L-glutamic acid in the solutions without IL was measured by UV spectroscopy and with a gravimetrical method. In the presence of an IL HPLC-analysis was applied. The solid phases were characterized using Raman spectroscopy and powder X-ray diffraction to distinguish the amino acids from their salts. While the solubility of L-alanine did not depend on pH within the considered pH range, the solubility of L-glutamic acid strongly increased with increasing pH. Below pH 6.2 the solid phase was characterized to be L-glutamic acid, while sodium L-glutamate monohydrate was found to be the solid at pH higher than 6.2. It could be observed that the solubility of sodium L-glutamate monohydrate was comparatively high, and increased with increasing pH. Upon addition of the ILs under investigation ([bmim][OTf]) and [ch][dhcit]) the solubility of L-alanine and L-glutamic acid was decreased. Original PC-SAFT was applied to predict the solubility of L-alanine and L-glutamic acid (and its sodium salt) in water, with and without the ILs under consideration, at the experimental conditions with quantitative agreement to the experimental data. (Graph Presented).

UR - http://www.scopus.com/inward/record.url?scp=85019100121&partnerID=8YFLogxK

U2 - 10.1021/acs.jced.6b00367

DO - 10.1021/acs.jced.6b00367

M3 - Article

AN - SCOPUS:85019100121

VL - 62

SP - 52

EP - 61

JO - Journal of Chemical & Engineering Data

JF - Journal of Chemical & Engineering Data

SN - 0021-9568

IS - 1

ER -