Use of peak sharpening effects to improve the separation of chiral compounds with molecularly imprinted porous polymer layer open‐tubular capillaries

Advancements of chiral molecularly imprinted polymers in separation and sensor fields: A review of the last decade

Since chiral recognition mechanism based on molecularly imprinted polymers immerged, it has assisted countless chemical and electrochemical analytical sample preparation techniques. It has done this by enhancing the enatioseparation abilities of these techniques. The preparation and optimization of chiral molecularly imprinted polymers (CMIPs) are two favored methods in the separation and sensor fields. This review aims to present an overview of advances in the preparation and application of CMIPs in analytical approaches in different available formats (eg. column, monolithic column, cartridge, membrane, nanomaterials, pipette tip and stir bar sorptive) over the last decade. In addition, progress in the preparation and development of CMIPs-based sensor fields have been also discussed. Finally, the main application challenges of CMIPs are also summarily explained, as well as upcoming prospects in the field.

Recent advancements in open-tubular liquid chromatography and capillary electrochromatography during 2014-2018

This review critically discusses the developments on open-tubular liquid chromatography (OT-LC) and open-tubular capillary electrochromatography (OT-CEC) during 2014-2018. An appropriate Scopus search revealed 5 reviews, 4 theoretical papers on open-tubular format chromatography, 29 OT-LC articles, 68 OT-CEC articles and 4 OT-LC/OT-CEC articles, indicating a sustained interest in these areas. The open-tubular format typically uses a capillary column with inner walls that are coated with an ample layer or coating of solid stationary phase material. The ratio between the capillary internal diameter and coating thickness (CID/CT) is ideally ≤ 100 for appropriate chromatographic retention. We, therefore, approximated the CID/CT ratios and found that 22 OT-LC papers have CID/CT ratios ≤100. The other 7 OT-LC papers have CID/CT ratio >100 but have clearly demonstrated chromatographic retention. These 29 papers utilised reversed phase or ion exchange mechanisms using known or innovative solid stationary phase materials (e.g. metal organic frameworks), stationary pseudophases from ionic surfactants or porous supports. On the other hand, we found that 68 OT-CEC papers, 7 OT-LC papers and 4 OT-LC & OT-CEC papers have CID/CT ratios >100. Notably, 44 papers (42 OT-CEC and 2 OT-LC & OT-CEC) did not report the retention factor and/or effective electrophoretic mobility of analytes. Considering all covered papers, the most popular activity was on the development of new chromatographic materials as coatings. However, we encourage OT-CEC researchers to not only characterise changes in the electroosmotic flow but also verify the interaction of the analytes with the coating. In addition, the articles reported were largely driven by stationary phase or support development and not by practical applications.

Recent developments in open tubular capillary electrochromatography from 2016 to 2017

Interest in open-tubular capillary electrochromatography (OT-CEC) continues to thrive because of the inherent advantage of OT-CEC combining the high efficiency of capillary electrophoresis and the high selectivity of high performance liquid chromatography. For the period 2016 to 2017, novel materials have been developed as first-time stationary phases for OT-CEC and are grouped in this review as polymer-based materials, frameworks, nanoparticles, graphene-based materials, and biomaterials. Coating and fabrication methods mostly rely on covalent coating strategies while non-covalent immobilisation strategies like electrostatic assembly are notably still being employed. The concern of overcoming phase ratio challenges in OT-CEC coatings have also generated adoption of combined coating strategies including multi-layering, layer-by-layer self-assembly and methods adapted from nanofilm fabrications like epitaxial growth, liquid phase deposition, or nucleation of crystal growth. The emergence of non-conventional coating characterisation methods such as transmission electron microscopy, X-ray diffraction or X-ray photoelectron spectroscopy is also discussed.