1 research outputs found
Influence of pH Value and Ionic Liquids on the Solubility of l‑Alanine and l‑Glutamic Acid in Aqueous Solutions at 30 °C
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]Â[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]Â[OTf])
and [ch]Â[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