Enantiomeric separation of glycidyl tosylate by CE: Application to the study of catalytic asymmetric epoxidation of allyl alcohol

Abstract

A CE method using CDs as chiral selectors was developed and validated to achieve the separation of glycidyl tosylate enantiomers originated by in situ derivatization of glycidol enantiomers obtained in asymmetric epoxidation of allyl alcohol with chiral titanium-tartrate complexes as catalysts. The effects of the nature, pH and concentration of the buffer, the nature and concentration of chiral selector, the addition of SDS, methanol, ethanol or 2-propanol, the capillary temperature, the effective capillary length and the applied voltage on the chiral resolution of glycidyl tosylate enantiomers were investigated. The best separation conditions were achieved using a Tris-borate buffer mixture (50 and 25 mM, respectively) at pH=9.3 with a dual CD system consisting of 2.5% succinyl-beta-CD and 1.0% beta-CD w/v at 15 degrees C. A baseline separation (resolution approximately 2.0) of the glycidyl tosylate enantiomers was obtained in a relatively short time (less than 12 min). Satisfactory results were obtained in terms of linearity (r>0.99) and intermediate precision (RSD below 8.5%). The LOD and LOQ were 3.0 and 10.0 mg/L, respectively, and the recoveries ranged from 99.8 to 108.8%. Finally, the method was applied to the determination of the enantiomeric excess and the yield obtained in the asymmetric epoxidation of allyl alcohol employing chiral titanium-tartrate complexes as catalysts after an in situ derivatization of glycidol enantiomers to glycidyl tosylate.

Improving the sensitivity in chiral capillary electrophoresis

“…This is the most remarkable sensitivity improvement from all the works included in this review which is also the work reporting the lowest LOD (8-40 × 10 −11 M). The excellent sensitivity of this methodology is demonstrated when compared to previously reported works, this methodology being five times more sensitive than SPE-HPLC [57] and isotachophoresis CE [58] methodologies and 30 times more sensitive than an FESI-EKC method [59].…”

Sensitive enantioanalysis of β‐blockers via field‐amplified sample injection combined with water removal in microemulsion electrokinetic chromatography

“…The LODs of the method, calculated as three times of S/N value, were 0.10, 0.10, 0.12, 0.11, 0.02, and 0.02 ng/mL for S-BU, R-BU, S-AL, R-AL, S-PRO, and R-PRO, respectively. Compared with the LOD of 0.4, 0.2 ß 0.5, and 29.6 ß 35.5 ng/mL in previous reports using SPE-HPLC [10], t-ITP-CZE [21], and FESI-CDCZE [38], respectively, the higher sensitivity of the method indicated its superior practical utility in trace content compounds in biological fluids.…”

“…Therefore, the chiral separation and determination of the stereochemical composition or stereochemical purity of ␤-blocker drugs are essential for diagnostic purposes and therapeutic drug monitoring. Methods for the separation and determination of ␤-blocking drugs include HPLC [6][7][8][9][10], CE [11], and flow injection analysis (FIA) [12]. Compared to other techniques, CE has become popular as versatile technique for enantioseparation because of the advantages of its own, especially the various separation modes [11,13].…”

Chiral selectors in CE: Recent developments and applications

“…The combination though of two CSs may result in improved resolutions. The most frequently used dual selector systems, which provide successful enantioseparations, include different CDs, usually anionic with neutral CD derivatives or with native CDs or two neutral CDs derivatives .…”