[Solubility behavior of four diastereomeric salts and two amino acids in near-critical CO2].
OBJECTIVE
To establish a suitable condition for extraction of phenylalanine (Phe), 5-hydroxytryptophan (5-OH-Trp) and four diastereomeric salts, (1R,2S)-ephedrine- (2S,3S)-tartaric acid, (1R,2S)-ephedrine-(2R,3R)-tartaric acid, (1S,2S)-pseudoephedrine-(2S,3S)-tartaric acid, (1S,2S)-pseudoephedrine- (2R,3R)-tartaric acid in supercritical fluid extraction and to assess the solubilities of Phe, 5-OH-Trp and the four diastereomeric salts in CO2.


METHODS
Single-pass method and HPCE.


RESULTS
The solubilities of Phe, 5-OH-Trp and the four diastereomeric salts in CO2 were determined over temperature and pressure ranges of 25-50 degrees C and 6.32-34.03 MPa respectively. The experimental results showed that the solubilities of Phe, 5-OH-Trp and the four diastereomeric salts do not increase with density of CO2. There existed a maximum in the critical region of CO2.


CONCLUSIONS
The dramatically high solubilities in the pressure of 6.32-7.78 MPa show a critical behavior, which can be explained by critical characteristic through thermodynamics analysis. The results suggest that the separation of Phe, 5-OH-Trp and the four diastereomeric salts is more efficient in critical region of CO2.
Gao
Li-hong
LH
Department of Pharmacy, Changhai Hospital, Second Military Medical University, Shanghai 200433, China. gaolh2002@sohu.com
Liu
Hong-lai
HL
Chai
Shui-hong
SH
Cai
Yi-feng
YF
Liu
Li-li
LL
Wu
Yu-tian
YT
D006916:5-Hydroxytryptophan / Q000737:chemistry*; D004809:Ephedrine / Q000737:chemistry*; D010649:Phenylalanine / Q000737:chemistry*; D011312:Pressure; D012995:Solubility; D013237:Stereoisomerism; D013644:Tartrates / Q000737:chemistry*; D013696:Temperature
D013644:Tartrates; D010649:Phenylalanine; D006916:5-Hydroxytryptophan; D004809:Ephedrine; C029768:tartaric acid