Rapid fabrication of ionic liquid-functionalized monolithic column via in-situ urea-formaldehyde polycondensation for pressurized capillary electrochromatography

Rapid preparation and characterization of a bridged bis(β-cyclodextrin) functionalized urea–formaldehyde monolithic column by a “one-pot” approach

A new bridged-CD monolith was prepared by “one-pot” method within 30 minutes. The obtained bridged-CD monolith showed satisfactory enantioselectivity compared to a native-CD monolith.

Highly efficient preparation of β-CD-based chiral monolithic column by "one-pot" hydroxymethyl polycondensation for enantioseparation in capillary liquid chromatography

A facile strategy for highly efficient fabrication of chiral monolithic column was carried out by the simple "one-pot" hydroxymethyl polycondensation of native β-cyclodextrin (β-CD) and urea-formaldehyde (UF). In-situ rapid substitution of native β-CD and efficient polycondensation of β-CD products and UF oligomers was proposed and fulfilled in one pot. The feasibility, mechanism and key parameters of polycondensation reaction were discussed. The data on crosslinking polycondensation and reaction kinetics were further evaluated. Characteristics including the morphologies, permeability and structure stability of the resultant monolithic columns were also studied. Under the optimal conditions, the "one-pot" hydroxymethyl polycondensation was accomplished in an aqueous solution within only 10 mins. Satisfactory stability and repeatability were gained, and good enantioseparation of eight model enantiomers was successfully achieved with the resultant β-CD-based monolith. It was simple and highly efficient, and the organic solvents, special CD derivatives and tediously long-time polymerization reaction were successfully avoided, which might light a new access to rapid preparation of CD-chiral monolith for high-performance enantioseparation.

An underestimated technique. Does pressurized and pressure-assisted capillary electrochromatography have potential in drug and pharmacological-active compounds analysis?

Pharmaceutical analysis guarantees patient safety all over the world. Thus, continuous development of existing analytical techniques is still very important. Pressurized capillary electrochromatography and pressure-assisted capillary electrochromatography are hybrid separation techniques that combine the selectivity of liquid chromatography and the high separation efficiency of capillary electrophoresis. They use a smaller amount of reagents and samples, hence, reducing the total cost of analysis. Therefore they have found application in a number of pharmaceutical and biomedical analysis. This review article focuses on the use and importance of pressurized and pressure-assisted capillary electrochromatography in pharmaceutical and biomedical analysis, taking into account types of detectors and capillaries used. Despite the fact that pressurized capillary electrochromatography and pressure assisted capillary electrochromatography offer many possibilities and have been available for over a dozen years, they are still underdevelopment and not fully explored.

Advances in capillary electro-chromatography

Capillary electrochromatography (CEC) is a micro-scale separation technique which is a hybrid between capillary electrophoresis (CE) and liquid chromatography (LC). CEC can be performed in packed, monolithic and open-tubular columns. In recent three years (from 2016 to 2018), enormous attention for CEC has been the development of novel stationary phases. This review mainly covers the development of novel stationary phases for open-tubular and monolithic columns. In particular, some biomaterials attracted increasing interest. There are no significant breakthroughs in technology and principles in CEC. The typical CEC applications, especially chiral separations are described.

Preparation and evaluation of highly hydrophilic aptamer-based hybrid affinity monolith for on-column specific discrimination of ochratoxin A

Nonspecific adsorption is a challenge of specific recognition on aptamer-based affinity monoliths. Here, a novel highly hydrophilic polyhedral oligomeric silsesquioxane (POSS)-containing aptamer-based hybrid-silica affinity monolith with a good recognition nature was prepared and used for specific discrimination of ochratoxin A (OTA). A homogeneous polymerization mixture consisted of POSS chemicals, hydrophilic monomers and aptamer solution was directly polymerized via the "one-pot" method. Preparation and characterization of the resultant affinity monolith were studied in detail. A highly hydrophilic nature was obtained and the typical hydrophilic interaction liquid chromatography (HILIC) was observed when acetonitrile (ACN) content in mobile phase was 25%, which reached the highest hydrophilicity of POSS-based hybrid monoliths. By using OTA as model analyte, the nonspecific adsorption was effectively suppressed. The recovery of the analogue ochratoxin B (OTB) was only about 0.1% even if the content of OTB was 50 times more than OTA, which was much better than other POSS-containing monoliths and polar siloxane-based hybrid monoliths. Applied to beer samples, the adsorption of background materials was drastically resisted, and efficient recognition of OTA was obtained with the recoveries of 94.9-99.8%. Much less disturbance was observed than that occurred in hydrophobic POSS-based affinity monolith. It lights an attractive implement with high hydrophilicity and specificity for online selective recognition of OTA.

An innovative reversed-phase monolithic column modified with 4-vinylbiphenyl and ionic liquid stationary phases for capillary electrochromatography

A poly(VBP-co-EDMA-co-IL) monolithic column was used for electrochromatographic separation.

Recent advances in mixed-mode chromatographic stationary phases

Mixed-mode phases have become very popular in the last decade, and the number of new mixed/multi-mode sorbents is growing fast. Unlike single-mode stationary phases, perfectly suited for the separation of the analytes possessing similar physicochemical properties, for instance reversed-phase chromatography for hydrophobic solutes, mixed-mode sorbents providing multimodal interactions can render better separation selectivity for complex mixtures of solutes differing significantly in their physicochemical characteristics. The most frequent modern mixed-mode stationary phases are di/tri-mode sorbents embracing the following interactions, hydrophobic, electrostatic (coulombic), and hydrophilic. According to their structures, it is possible to distinguish silica-based, polymer-based, hybrid, and monolithic mixed-mode stationary phases. Herewith, newly synthesized mixed-mode sorbents developed within the last two and half years are categorized, discussed, and summarized. The main attention is devoted to the description of the synthetic routes and characterization methods applied for the new stationary phases.

Sensitive profiling of trace neurotoxin domoic acid by pressurized capillary electrochromatography with laser-induced fluorescence detection

A stable, sensitive and low-reagent consumption method for the quantification of trace neurotoxin domoic acid (DA) was presented by pressurized capillary electrochromatography (pCEC) with laser-induced fluorescence (LIF) detection.