Colistin Sulfate Chiral Stationary Phase for the Enantioselective Separation of Pharmaceuticals Using Organic Polymer Monolithic Capillary Chromatography

Synergistic enantioseparation system based on a novel nanomaterial synthesized by chiral metal-organic framework and chiral molecularly imprinted polymer in capillary electrochromatography

A capillary electrochromatography (CEC) synergistic enantioseparation system based on a novel nanomaterial synthesized by chiral molecularly imprinted polymers (CMIPs) and chiral metal organic frameworks (CMOFs) was developed. Compared with CMIPs and CMOFs alone, the enantioseparation performance of ofloxacin (OFL) of the CEC with the novel nanomaterial as stationary phases was greatly improved. CMOFs with chiral recognition ability have synergize with CMIPs to greatly improve the chiral selectivity of the novel stationary phases in CEC. As a proof-of-concept demonstration, a coated capillary column was prepared by a sol-gel method using S-OFL (template), iron-based cyclodextrin MOF (Fe-CD-MOF, a CMOF), 3-aminopropyltriethoxysilane (functional monomer), and tetraethyl orthosilicate (cross-linking agent). Then, the newly constructed CEC system has excellent enantioseparation performance of OFL with a resolution of 3.92. Finally, computerized molecular docking revealed that the difference in the binding ability of Fe-CD-MOF to ofloxacin enantiomers was an important mechanism for CEC chiral separation. This innovative development of synergistic chiral stationary phases based on CMOFs and CMIPs creates a highly efficient potential direction for enantiomer separation.

Lipase as a Chiral Selector Immobilised on Carboxylated Single-Walled Carbon Nanotubes and Encapsulated in the Organic Polymer Monolithic Capillary for Nano-High Performance Liquid Chromatography Enantioseparation of Racemic Pharmaceuticals

Herein, we report the preparation of lipase immobilised on single-walled carbon nanotubes (SWCNTs) as an enantioselector for capillary monolithic columns and their application in the chiral separation of racemic pharmaceuticals. The columns were prepared through the encapsulation of functionalised SWCNTs (c-SWCNTs) within an organic monolithic polymer, followed by the immobilisation of lipase over the obtained monolith, over a three-day (L1) and five-day (L2) period. The prepared columns were tested for the enantioselective nano-HPLC separation of 50 racemic drugs. A suitable resolution was achieved for 25 drugs using nano-RP-HPLC conditions for both the L1 and L2 capillaries, while no specific resolution was detected under normal-phase HPLC conditions. The developed c-SWCNT-lipase-based polymeric monolithic capillaries are a promising expansion for separating pharmaceutical enantiomers' using nano-HPLC.

Macrocyclic Antibiotics as Effective Chiral Selectors in Liquid Chromatography for Enantiomeric Separation of Pharmaceutical Compounds: A Review

Chiral separation techniques play a crucial role in the pharmaceutical industry, where the enantiomeric purity of drugs can have a significant impact on their efficacy and safety. Macrocyclic antibiotics are highly effective chiral selectors used in various chiral separation techniques, including LC, HPLC, SMB, and TLC, offering reproducible results and a wide range of applications. However, developing robust and efficient immobilization mechanisms for these chiral selectors remains a challenge. This review article focuses on various immobilization approaches, such as immobilization, coating, encapsulation, and photosynthesis, that have been applied to immobilize macrocyclic antibiotics on their support. Commercially available macrocyclic antibiotics for conventional liquid chromatography include Vancomycin, Norvancomycin, Eremomycin, Teicoplanin, Ristocetin A, Rifamycin, Avoparcin, Bacitracin, and others. In addition, capillary (nano) liquid chromatography has also been used in chiral separation utilizing Vancomycin, Polymyxin B, Daptomycin, and Colistin Sulfate. Macrocyclic antibiotic-based CSPs have been extensively applied due to their reproducible results, ease of use, and broad range of applications, capable of separating a large number of racemates.

Enantioseparation/Recognition based on nano techniques/materials

Enantiomers show different behaviors in interaction with the chiral environment. Due to their identical chemical structure and their wide application in various industries, such as agriculture, medicine, pesticide, food, and so forth, their separation is of great importance. Today, the term "nano" is frequently encountered in all fields. Technology and measuring devices are moving towards miniaturization, and the usage of nanomaterials in all sectors is expanding substantially. Given that scientists have recently attempted to apply miniaturized techniques known as nano-liquid chromatography/capillary-liquid chromatography, which were originally accomplished in 1988, as well as the widespread usage of nanomaterials for chiral resolution (back in 1989), this comprehensive study was developed. Searching the terms "nano" and "enantiomer separation" on scientific websites such as Scopus, Google Scholar, and Web of Science yields articles that either use miniaturized instruments or apply nanomaterials as chiral selectors with a variety of chemical and electrochemical detection techniques, which are discussed in this article.

A Polymer-based Monolithic Capillary Column with Polymyxin-B Chiral Selector for the Enantioselective Nano-High Performance Liquid Chromatographic Pharmaceutical Analysis

Herein, we report the first use of Polymyxin-B antibiotic as a enantio-selector in polymer monolithic capillary. The capillaries were functionalised, characterized and tested for the enantioselective nano-HPLC separation of 50 racemic pharmaceutical drugs. They have been easily prepared by immobilizing Polymyxin-B over the organic polymer for 48 h (P1) or encapsulating Polymyxin-B within the organic polymer (P2) and tested for the enantioselective resolution of racemic drugs. Acceptable resolution was achieved for 21 drugs using RP-HPLC conditions on both (P1) and (P2) capillary columns, while no separation was observed under NP-HPLC conditions. Polymyxin-B is commercially available, easily solubilized and stable in both acidic and neutral media. The developed Polymyxin-B-based polymer monolithic capillaries provide a promising expansion of platform in enantioselective HPLC separations.

Chiral Nano-Liquid Chromatography and Dispersive Liquid-Liquid Microextraction Applied to the Analysis of Antifungal Drugs in Milk

A novel chromatographic application in chiral separation by using the nano-LC technique is here reported. The chiral recognition of 12 antifungal drugs was obtained through a 75 µm I.D. fused-silica capillary, which was packed with a CSP-cellulose 3,5-dichlorophenylcarbamate (CDCPC), by means of a lab-made slurry packing procedure. The mobile phase composition and the experimental conditions were optimized in order to find the optimum chiral separation for some selected racemic mixtures of imidazole and triazole derivatives. Some important parameters, such as retention faction, enantioresolution, peak efficiency, and peak shape, were investigated as a function of the mobile phase (pH, water content, type and concentration of both the buffer and the organic modifier, and solvent dilution composition). Within one run lasting 25 min, at a flow rate of approximately 400 nL min^-1, eight couples of enantiomers were baseline-resolved and four of them were separated in less than 25 min. The method was then applied to milk samples, which were pretreated using a classical dispersive liquid-liquid microextraction technique preceded by protein precipitation. Finally, the DLLME-nano-LC-UV method was validated in a matrix following the main FDA guidelines for bioanalytical methods.

Chiral Monolithic Silica-Based HPLC Columns for Enantiomeric Separation and Determination: Functionalization of Chiral Selector and Recognition of Selector-Selectand Interaction

This review draws attention to the use of chiral monolithic silica HPLC columns for the enantiomeric separation and determination of chiral compounds. Properties and advantages of monolithic silica HPLC columns are also highlighted in comparison to conventional particle-packed, fused-core, and sub-2-µm HPLC columns. Nano-LC capillary monolithic silica columns as well as polymeric-based and hybrid-based monolithic columns are also demonstrated to show good enantioresolution abilities. Methods for introducing the chiral selector into the monolithic silica column in the form of mobile phase additive, by encapsulation and surface coating, or by covalent functionalization are described. The application of molecular modeling methods to elucidate the selector–selectand interaction is discussed. An application for enantiomeric impurity determination is also considered.

Recent Applications of Nano-Liquid Chromatography in Food Safety and Environmental Monitoring: A Review

In recent years, a trend toward instrument miniaturization has led to the development of new and sophisticated analytical systems, such as nano-liquid chromatography (nano-LC), which has enabled improvements of sensitivity, as well as chromatographic resolution. The growing interest in nano-LC methodology has resulted in a variety of innovative and promising applications. In this article, we review the applications of nano-LC separation methods coupled with mass spectrometry in the analysis of food and environmental samples. An assessment of sample preparation methods and analytical performance are provided, along with comparison to other, more established analytical techniques. Three main groups of compounds that are crucial for food safety assessment are considered in this review: pharmaceuticals (including antibiotics), pesticides, and mycotoxins. Recent practical applications of the nano-LC method in the determination of these compounds are discussed. Furthermore, we also focus on methods for the determination of various environmental contaminants using nano-LC methods. Future perspectives for the development of nano-LC methods are discussed.

Daptomycin: A Novel Macrocyclic Antibiotic as a Chiral Selector in an Organic Polymer Monolithic Capillary for the Enantioselective Analysis of a Set of Pharmaceuticals

Daptomycin, a macrocyclic antibiotic, is here used as a new chiral selector in preparation of chiral stationary phase (CSP) in a recently prepared polymer monolithic capillary. The latter is prepared using the copolymerization of the monomers glycidyl methacrylate (GMA) and ethylene glycol dimethacrylate (EGDMA) in the presence of daptomycin in water. Under reversed phase conditions (RP), the prepared capillaries were tested for the enantioselective nanoliquid chromatographic separation of fifty of the racemic drugs of different pharmacological groups, such as adrenergic blockers, H1-blockers, NSAIDs, antifungal drugs, and others. Baseline separation was attained for many drugs under RP-HPLC. Daptomycin expands the horizon of chiral selectors in HPLC.

Recent developments of monolithic and open-tubular capillary electrochromatography (2017-2019)

Capillary electrochromatography, which combined the high selectivity of high-performance liquid chromatography and the high separation efficiency of capillary electrophoresis, is an attractive separation tool. In this review, the developments on monolithic and open tubular capillary electrochromatography during 2017 to August 2019 are summarized. Considering the development of novel stationary phases is the most active research field in capillary electrochromatography, monolithic capillary electrochromatography is classified according to the polymer-based and hybrid monolithic columns, while open-tubular capillary electrochromatography is categorized by cyclodextrin, silica, polymer, nanomaterials, microporous materials, and biomaterials-based open tubular columns.