Effect of Temperature on Chiral Separation of Ketamine Enantiomers by High‐Performance Liquid Chromatography

Abstract

A semipreparative column packed with microcrystalline cellulose triacetate (MCTA) was used to separate ketamine enantiomers by high‐performance liquid chromatography (HPLC). The effect of temperature on the kinetics of mass transfer and equilibrium constants were evaluated by the moment analysis at 303, 313, and 323 K. Total porosity, bed porosity, and equilibrium constants were measured by the first moment. Pore diffusion and axial dispersion coefficients were evaluated by the second moment. It was observed that band broadening decreased with increasing temperature. The equilibrium constants were found to be greater than unity and decreasing with increasing temperature. The pore diffusion coefficients increased with increasing temperature and the main contribution to the band broadening was attributed to low mass transfer kinetics. The pore diffusion coefficients controlled the mass‐transfer process in MCTA column. These results may be used to the determination of operating conditions and computational simulation of a chromatographic separation in simulated moving bed unity.     

Kinetic Study for Biphasic Recognition Chiral Extraction of Naproxen Enantiomers with Hydrophobic L-iso-butyl Tartrate and Hydrophilic Hydroxypropyl-β-Cyclodextrin

The kinetics of biphasic recognition chiral extraction of naproxen (HA) enantiomers was investigated to determine the extraction mechanism, with hydrophobic L-iso-butyl tartrate (L-IBTA) in the organic phase and hydrophilic hydroxypropyl-β-cyclodextrin (HP--CD) in the aqueous phase. The two-phase homogeneous reaction model was selected over the interfacial reaction model, because there is a clear physical solubility of naproxen enantiomers in both the aqueous phase and the organic phase. The reactions between the HA enantiomers and L-iso-butyl tartrate in a stirred cell fall in Regime 3; the extraction is accompanied by two fast chemical reactions in the diffusion film. The reactions have been found to be first order with respect to HA enantiomers and second order with respect to L-IBTA. The forward rate constants for S-HA and R-HA are 1.26?×?10^?4 mol^?2 m⁶ s^?1 and 2.52?×?10^?4 mol^?2 m⁶ s^?1, respectively. With the increase of HP--CD concentration in the aqueous phase, high enantioselectivity was obtained, but the extraction rates decreased. These data will be useful in the design of extraction processes.     

Enantioselective Separation of Racemic Amlodipine by Two-Phase Chiral Extraction Containing O,O′-Dibenzoyl-(2S,3S)-Tartaric Acid as Chiral Selector

A two-phase chiral extraction system containing O,O′-dibenzoyl-(2S,3S)-tartaric acid ((+)-DBTA) in 1-decanol organic phase and aqueous phase was developed for the chiral resolution of amlopidine. The effects of extractant concentration, equilibrium time, and pH of the aqueous phase on the separation performance were investigated. The results indicated that the system afforded a strong chiral separation ability; the (+)-DBTA showed a higher recognition ability toward (S)-amlodipine than the (R)-amlodipine. Upon a single extraction, the enantiomeric excess (%) of (S)-amlodipine could be enriched to 24.27%. The product recovery ratio was 0.74. The distribution ratios for (S)-amlodipine (D _S ), (R)-amlodipine (D _R ) and separation factor (α) were 1.28, 0.78, and 1.64, respectively. Therefore, the pH and concentration of the extractant have the great effects on chiral separation ability. Two-phase chiral extraction has great significance for preparative separation of (S)-amlodipine; it can also be used to design and scale up the enantioselective separation process.     

Polymerization of Butyl Acrylate using Potassium Peroxy Disulfate as Initiator in the Presence of Phase Transfer Catalyst—A Kinetic Study

The kinetics and mechanism of free radical polymerization of butyl acrylate (BA), using potassium peroxydisulfate (K₂S₂O₈) as initiator in the presence of propiophenonebenzyldimethylammonium chloride (PPBDMAC) as phase transfer catalyst (PTC) has been studied. The reactions were carried out under inert, unstirred conditions and at a constant temperature of 60°C in cyclohexanone/water biphase media. The dependence of the rate of polymerization (R_p) on various experimental conditions such as different concentrations of monomer, initiator, phase transfer catalyst, varying acid and ionic strength, temperature, and volume fraction of aqueous phase were studied. The order with respect to monomer, initiator, and the phase transfer catalyst were found to be 1.5, 0.5, and 0.5, respectively. The rate of polymerization was independent of acid and ionic strength. Based on the results, a mechanism has been proposed for the polymerization reaction.     

Studies on the Development of a Two Stage SLM System for the Separation of Carrier‐free 90Y using KSM‐17 and CMPO as Carriers

Abstract

Solvent extraction studies of Y³⁺ and Sr²⁺ with 2‐ethylhexyl 2‐ethylhexyl phosphonic acid (KSM‐17) and octyl(phenyl)‐N,N‐diisobutylcarbamoylmethylphosphine oxide (CMPO) are carried out from aqueous media containing a wide range of nitric acid and other potential reagents to arrive at the operating conditions for the selective transport of ⁹⁰Y using supported liquid membrane (SLM) containing these reagents as carriers. Since the transport data of ⁹⁰Y using single cell SLM with KSM‐17 was available from our earlier experiments, single cell transport studies with CMPO carrier are only carried out to optimize the strippant phase. Transport studies with pure ⁹⁰Y is carried out using a transport cell with two SLMs one with KSM‐17 and the other CMPO carriers to optimize the transport parameters. Based on these data the development of a two stage SLM system for the generation of carrier free ⁹⁰Y from ⁹⁰Sr source is described. The procedure described is amenable for automation and scale up.