Tian Yao

A resolution approach of racemic phenylalanine with aqueous two-phase systems of chiral tropine ionic liquids

Aqueous two-phase systems (ATPS) based on tropine type chiral ionic liquids and inorganic salt solution were designed and prepared for the enantiomeric separation of racemic phenylalanine. The phase behavior of IL-based ATPS was comprehensive investigated, and phase equilibrium data were correlated by Merchuk equation. Various factors were also systematically investigated for their influence on separation efficiency. Under the appropriate conditions (0.13g/g [C8Tropine]pro, 35mg/g Cu(Ac)2, 20mg/g d,l-phenylalanine, 0.51g/g H2O and 0.30g/g K2HPO4), the enantiomeric excess value of phenylalanine in solid phase (mainly containing l-enantiomer) was 65%. Finally, the interaction mechanism was studied via 1D and 2D NMR. The results indicate that d-enantiomer of phenylalanine interacts more strongly with chiral ILs and Cu(2+) based on the chiral ion-pairs space coordination mechanism, which makes it tend to remain in the top IL-rich phase. By contrast, l-enantiomer is transferred into the solid phase. Above chiral ionic liquids aqueous two-phase systems have demonstrated obvious resolution to racemic phenylalanine and could be promising alterative resolution approach for racemic amino acids in aqueous circumstance.

Magnetic ionic liquid aqueous two-phase system coupled with high performance liquid chromatography: A rapid approach for determination of chloramphenicol in water environment

A novel organic magnetic ionic liquid based on guanidinium cation was synthesized and characterized. A new method of magnetic ionic liquid aqueous two-phase system (MILATPs) coupled with high-performance liquid chromatography (HPLC) was established to preconcentrate and determine trace amount of chloramphenicol (CAP) in water environment for the first time. In the absence of volatile organic solvents, MILATPs not only has the excellent properties of rapid extraction, but also exhibits a response to an external magnetic field which can be applied to assist phase separation. The phase behavior of MILATPs was investigated and phase equilibrium data were correlated by Merchuk equation. Various influencing factors on CAP recovery were systematically investigated and optimized. Under the optimal conditions, the preconcentration factor was 147.2 with the precision values (RSD%) of 2.42% and 4.45% for intra-day (n=6) and inter-day (n=6), respectively. The limit of detection (LOD) and limit of quantitation (LOQ) were 0.14ngmL-1 and 0.42ngmL-1, respectively. Fine linear range of 12.25ngmL-1-2200ngmL-1 was obtained. Finally, the validated method was successfully applied for the analysis of CAP in some environmental waters with the recoveries for the spiked samples in the acceptable range of 94.6%-99.72%. Hopefully, MILATPs is showing great potential to promote new development in the field of extraction, separation and pretreatment of various biochemical samples.

Synthesis, magnetism, aqueous-two phase formation and physical properties of novel guanidinium-based magnetic ionic liquids

Magnetic ionic liquids (MILs) are a new class of ionic liquids that reveal paramagnetic properties. In this study, a series of novel guanidinium-based organic magnetic ionic liquids were synthesized and characterized by FT-IR and ESI-MS. The magnetic properties of these MILs were investigated using a vibrating sample magnetometer. With decreasing length of the carbon chain of the MILs, magnetic susceptibility was observed to strengthen. MILs also showed extremely strong paramagnetism when the temperature dropped below 25 K. A new concept of a magnetic ionic liquid aqueous-two phase system (MILATPs) was proposed for the first time. Compared to the latest developments in separation systems, the advantages of magnetic separation, organic solvent free and rapid extraction were successfully combined together in the novel proposed MILATPs. Interestingly, all these novel compounds are capable of forming MILATPs and can respond to an external magnetic field to accelerate isolation of two phases. In addition, some physical properties such as density, electrical conductivity and acidity were further studied. These MILs are expected to show great potential for further application in the fields of catalysis, desulfurization, biotechnology, electrochemistry, and especially separation and pretreatment technology.

Determination and Correlation of Solubilities of Four Novel Benzothiazolium Ionic Liquids with PF−6 in Six Alcohols

Abstract Four novel benzothiazolium ionic liquids with PF−6([C1Bth][PF6], [C4Bth][PF6], [C5Bth][PF6] and [C6Bth][PF6]) were synthesized, and the rang of their melting points were determined between 358.35 K–424.05 K. The relationship of their melting points and the length of the straight alkyl chain on cation reflected ‘S’ type tendency. Then, the solubilities of the four ionic liquids in six lower alcohols (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol and 2-methyl-1-propanol) were measured in the temperature rang of 253.15–383.15 K at atmospheric pressure with static analytical method, respectively. It was found that [C6Bth][PF6] in all investigated ionic liquids had the largest solubility in six alcohols and the solubility of [C4Bth][PF6] in methanol was very sensitive for temperature in 313.15–333.15 K, which was so-called “temperature-sensitivity”. This feature is of great significance to their application of catalyzing reaction or extraction process, and makes the recovery and reuse of ionic liquids (ILs) become easier. Moreover, the experimental solubility data were correlated with the modified Apelblat equation and λh equation, respectively. It was found that the result of correlation using two divided temperature ranges was better than that of using the whole temperature range.

DEVELOPMENT OF AN EFFICIENT HPLC METHOD WITH PRE-COLUMN DERIVATIZATION FOR DETERMINATION OF ENANTIOMERIC PURITY OF 2-(AMINOMETHYL)-1-ETHYLPYRROLIDINE

The development of a simple and efficient analytical method for determination of enantiomeric purity of 2-(aminomethyl)-1-ethylpyrrolidine was presented. The method was based on pre-column derivatization of 2-(aminomethyl)-1-ethylpyrrolidine with 4-nitrobenzoic acid completing separation of the enantiomers on high performance liquid chromatographic (HPLC) chiral stationary phase (CSP). After optimizing all the effective parameters, the best performances were achieved on a Chiralcel OD-H analytical column (250 × 4.6 mm) using n-hexane: ethanol (98:2, v/v) containing 0.2% triethylamine as mobile phase with a flow rate of 1.0 mL min-1 at 25°C. Online UV and optical rotation (OR) detection was performed at 254 nm. The parameters which have an effect on chiral separation were investigated, including mobile phase additive, organic modifier type and concentration, column temperature and flow rate. The method was tested for precision, accuracy, linearity, limit of detection (LOD), limit of quantification (LOQ) and robustness. The present method is expected to be accurate, stable, rapid and sensitive and can be used for the determination of the enantiomeric purity of 2-(aminomethyl)-1-ethylpyrrolidine in bulk samples.