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2407 KiB

Open AccessArticle

Graphene Oxide Nanoparticles and Their Influence on Chromatographic Separation Using Polymeric High Internal Phase Emulsions

by Sidratul Choudhury, Emer Duffy, Damian Connolly, Brett Paull and Blánaid White

Separations 2017, 4(1), 5; https://doi.org/10.3390/separations4010005 - 11 Feb 2017

Cited by 8 | Viewed by 5703

Abstract

This work presents the first instance of reversed-phase liquid chromatographic separation of small molecules using graphene oxide nanoparticle-modified polystyrene-divinylbenzene polymeric high internal phase emulsion (GONP PS-co-DVB polyHIPE) materials housed within a 200-µm internal diameter (i.d.) fused silica capillary. The graphene oxide [...] Read more.

This work presents the first instance of reversed-phase liquid chromatographic separation of small molecules using graphene oxide nanoparticle-modified polystyrene-divinylbenzene polymeric high internal phase emulsion (GONP PS-co-DVB polyHIPE) materials housed within a 200-µm internal diameter (i.d.) fused silica capillary. The graphene oxide nanoparticle (GONP)-modified materials were produced as a potential strategy to increase both the surface area limitations and the reproducibility issues observed in monolithic stationary phase materials. GONP PS-co-DVB polyHIPEs were found to have a surface area up to 40% lower than unmodified polymeric high internal phase emulsion (polyHIPE) stationary phases. However, despite having a surface area significantly lower than that of the unmodified material, the GONP-modified polyHIPEs demonstrated superior analyte adsorption properties. Reducing the GONP material did not have any significant impact on elution order or retention factor of the analytes, which was most likely due to low GONP loading attributed to the 250-nm GONPs utilised. The lower surface area of GONP-modified polyHIPEs provided similar separation efficiency and increased repeatability from injection to injection resulting in % relative standard deviations (%RSDs) of less than 0.6%, indicating the potential offered by graphene oxide (GO)-modified polyHIPES in flow through applications such as adsorption or separation processes. Full article

(This article belongs to the Special Issue Monolithic Columns in Separation Sciences)

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5323 KiB

Open AccessArticle

Numerical Simulation of Fluid Dynamics in a Monolithic Column

by Kazuhiro Yamamoto and Yuuta Tajima

Separations 2017, 4(1), 3; https://doi.org/10.3390/separations4010003 - 11 Jan 2017

Cited by 2 | Viewed by 4856

Abstract

As for the measurement of polycyclic aromatic hydrocarbons (PAHs), ultra-performance liquid chromatography (UPLC) is used for PAH identification and densitometry. However, when a solvent containing a substance to be identified passes through a column of UPLC, a dedicated high-pressure-proof device is required. Recently, [...] Read more.

As for the measurement of polycyclic aromatic hydrocarbons (PAHs), ultra-performance liquid chromatography (UPLC) is used for PAH identification and densitometry. However, when a solvent containing a substance to be identified passes through a column of UPLC, a dedicated high-pressure-proof device is required. Recently, a liquid chromatography instrument using a monolithic column technology has been proposed to reduce the pressure of UPLC. The present study tested five types of monolithic columns produced in experiments. To simulate the flow field, the lattice Boltzmann method (LBM) was used. The velocity profile was discussed to decrease the pressure drop in the ultra-performance liquid chromatography (UPLC) system. Full article

(This article belongs to the Special Issue Monolithic Columns in Separation Sciences)

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2329 KiB

Open AccessCommunication

In Situ Measurement of Polymer Layer Thickness in Porous Layer Open Tubular (PLOT) Columns Using Optical Absorbance in the Near-IR Range

by David Collins, Ekaterina Nesterenko and Brett Paull

Separations 2016, 3(4), 34; https://doi.org/10.3390/separations3040034 - 12 Dec 2016

Cited by 1 | Viewed by 4915

Abstract

Highly reproducible fabrication of porous layer open tubular (PLOT) structures in fused silica capillaries is often challenging; thus, methods to measure layer thickness growth in real time represent a powerful tool for the production of such columns. The work presented herein demonstrates the [...] Read more.

Highly reproducible fabrication of porous layer open tubular (PLOT) structures in fused silica capillaries is often challenging; thus, methods to measure layer thickness growth in real time represent a powerful tool for the production of such columns. The work presented herein demonstrates the application of optical absorbance in the near-infrared (near IR) range for the in-process measurement of polymer layer growth inside fused silica capillaries during the fabrication of PLOT columns. The proposed technique can be used for both on- and off-line measurements of layer thickness for thermal- and photo- initiated polymerisation methods, performed in either polytetrafluoroethylene (PTFE)- or polyimide-coated capillaries. Measurements of layer thickness were carried out at λ 700 nm, using 100 μm and 8 μm optical fibres, yielding relative standard deviation (%RSD) values of 27% and 22%, respectively. Full article

(This article belongs to the Special Issue Monolithic Columns in Separation Sciences)

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895 KiB

Open AccessArticle

Description of the Retention and Peak Profile for Chromolith Columns in Isocratic and Gradient Elution Using Mobile Phase Composition and Flow Rate as Factors

by Elsa Cabo-Calvet, Casandra Ortiz-Bolsico, Juan J. Baeza-Baeza and María Celia García-Alvarez-Coque

Chromatography 2014, 1(4), 194-210; https://doi.org/10.3390/chromatography1040194 - 19 Nov 2014

Cited by 11 | Viewed by 9811

Abstract

The effect of the modifier concentration and flow rate on the chromatographic performance of a second generation Chromolith® RP-18e column, under isocratic and gradient elution with acetonitrile-water mixtures, was examined using four sulphonamides as probe compounds. The acetonitrile concentration was varied between 5 [...] Read more.

The effect of the modifier concentration and flow rate on the chromatographic performance of a second generation Chromolith® RP-18e column, under isocratic and gradient elution with acetonitrile-water mixtures, was examined using four sulphonamides as probe compounds. The acetonitrile concentration was varied between 5 and 55% (v/v), and the flow rate between 0.1 and 5.0 mL/min, keeping the other factors constant. The changes in both retention and peak profile were modelled, and used to build simple plots, where the logarithm of the retention factor was represented against the modifier concentration (in gradient elution, against the initial modifier concentration), and the half-widths or widths against the retention time (in gradient elution, against the time at the column outlet). A particular plot was needed for describing the retention of each sulphonamide, but due to the similar interaction kinetics, a unique plot described the changes in the half-widths for all four sulphonamides. The changes in retention with the flow showed that allegedly in the second generation Chromolith, the column deformation observed for the first generation Chromolith, with the applied pressure at increasing flow, is decreased. Full article

(This article belongs to the Special Issue Monolithic Columns in Separation Sciences)

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Review

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1419 KiB

Open AccessFeature PaperReview

Nano-Doped Monolithic Materials for Molecular Separation

by Caleb Acquah, Eugene Marfo Obeng, Dominic Agyei, Clarence M. Ongkudon, Charles K. S. Moy and Michael K. Danquah

Separations 2017, 4(1), 2; https://doi.org/10.3390/separations4010002 - 1 Jan 2017

Cited by 18 | Viewed by 8488

Abstract

Monoliths are continuous adsorbents that can easily be synthesised to possess tuneable meso-/macropores, convective fluid transport, and a plethora of chemistries for ligand immobilisation. They are grouped into three main classes: organic, inorganic, and hybrid, based on their chemical composition. These classes may [...] Read more.

Monoliths are continuous adsorbents that can easily be synthesised to possess tuneable meso-/macropores, convective fluid transport, and a plethora of chemistries for ligand immobilisation. They are grouped into three main classes: organic, inorganic, and hybrid, based on their chemical composition. These classes may also be differentiated by their unique morphological and physicochemical properties which are significantly relevant to their specific separation applications. The potential applications of monoliths for molecular separation have created the need to enhance their characteristic properties including mechanical strength, electrical conductivity, and chemical and thermal stability. An effective approach towards monolith enhancement has been the doping and/or hybridization with miniaturized molecular species of desirable functionalities and characteristics. Nanoparticles are usually preferred as dopants due to their high solid phase dispersion features which are associated with improved intermolecular adsorptive interactions. Examples of such nanomaterials include, but are not limited to, carbon-based, silica-based, gold-based, and alumina nanoparticles. The incorporation of these nanoparticles into monoliths via in situ polymerisation and/or post-modification enhances surface adsorption for activation and ligand immobilisation. Herein, insights into the performance enhancement of monoliths as chromatographic supports by nanoparticles doping are presented. In addition, the potential and characteristics of less common nanoparticle materials such as hydroxyapatite, ceria, hafnia, and germania are discussed. The advantages and challenges of nanoparticle doping of monoliths are also discussed. Full article

(This article belongs to the Special Issue Monolithic Columns in Separation Sciences)

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1712 KiB

Open AccessReview

Monoliths in Bioprocess Technology

by Vignesh Rajamanickam, Christoph Herwig and Oliver Spadiut

Chromatography 2015, 2(2), 195-212; https://doi.org/10.3390/chromatography2020195 - 17 Apr 2015

Cited by 22 | Viewed by 14531

Abstract

Monolithic columns are a special type of chromatography column, which can be used for the purification of different biomolecules. They have become popular due to their high mass transfer properties and short purification times. Several articles have already discussed monolith manufacturing, as well [...] Read more.

Monolithic columns are a special type of chromatography column, which can be used for the purification of different biomolecules. They have become popular due to their high mass transfer properties and short purification times. Several articles have already discussed monolith manufacturing, as well as monolith characteristics. In contrast, this review focuses on the applied aspect of monoliths and discusses the most relevant biomolecules that can be successfully purified by them. We describe success stories for viruses, nucleic acids and proteins and compare them to conventional purification methods. Furthermore, the advantages of monolithic columns over particle-based resins, as well as the limitations of monoliths are discussed. With a compilation of commercially available monolithic columns, this review aims at serving as a ‘yellow pages’ for bioprocess engineers who face the challenge of purifying a certain biomolecule using monoliths. Full article

(This article belongs to the Special Issue Monolithic Columns in Separation Sciences)

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696 KiB

Open AccessReview

Recent Advances and Uses of Monolithic Columns for the Analysis of Residues and Contaminants in Food

by Mónica Díaz-Bao, Rocío Barreiro, José M. Miranda, Alberto Cepeda and Patricia Regal

Chromatography 2015, 2(1), 79-95; https://doi.org/10.3390/chromatography2010079 - 10 Feb 2015

Cited by 19 | Viewed by 8521

Abstract

Monolithic columns are gaining interest as excellent substitutes to conventional particle-packed columns. These columns show higher permeability and lower flow resistance than conventional liquid chromatography columns, providing high-throughput performance, resolution and separation in short run times. Monoliths possess also great potential for the [...] Read more.

Monolithic columns are gaining interest as excellent substitutes to conventional particle-packed columns. These columns show higher permeability and lower flow resistance than conventional liquid chromatography columns, providing high-throughput performance, resolution and separation in short run times. Monoliths possess also great potential for the clean-up and preparation of complex mixtures. In situ polymerization inside appropriate supports allows the development of several microextraction formats, such as in-tube solid-phase and pipette tip-based extractions. These techniques using porous monoliths offer several advantages, including miniaturization and on-line coupling with analytical instruments. Additionally, monoliths are ideal support media for imprinting template-specific sites, resulting in the so-called molecularly-imprinted monoliths, with ultra-high selectivity. In this review, time-saving LC columns and preparative applications applied to the analysis of residues and contaminants in food in 2010–2014 are described, focusing on recent improvements in design and with emphasis in automated on-line systems and innovative materials and formats. Full article

(This article belongs to the Special Issue Monolithic Columns in Separation Sciences)

4254 KiB

Open AccessReview

Development of Monolithic Column Materials for the Separation and Analysis of Glycans

by Allan J. Alla and Keith J. Stine

Chromatography 2015, 2(1), 20-65; https://doi.org/10.3390/chromatography2010020 - 9 Feb 2015

Cited by 12 | Viewed by 12371

Abstract

Monolithic column materials offer great advantages as chromatographic media in bioseparations and as solid-supports in biocatalysis. These single-piece porous materials have an interconnected ligament structure that limits the void volume inside the column, thus increasing the efficiency without sacrificing the permeability. The preparation [...] Read more.

Monolithic column materials offer great advantages as chromatographic media in bioseparations and as solid-supports in biocatalysis. These single-piece porous materials have an interconnected ligament structure that limits the void volume inside the column, thus increasing the efficiency without sacrificing the permeability. The preparation of monolithic materials is easy, reproducible and has available a wide range of chemistries to utilize. Complex, heterogeneous and isobaric glycan structures require preparation methods that may include glycan release, separation and enrichment prior to a comprehensive and site-specific glycosylation analysis. Monolithic column materials aid that demand, as shown by the results reported by the research works presented in this review. These works include selective capture of glycans and glycoproteins via their interactions with lectins, boronic acids, hydrophobic, and hydrophilic/polar functional groups on monolith surfaces. It also includes immobilization of enzymes trypsin and PNGase F on monoliths to digest and deglycosylate glycoproteins and glycopeptides, respectively. The use of monolithic capillary columns for glycan separations through nano-liquid chromatography (nano-LC) and capillary electrochromatography (CEC) and coupling these columns to MS instruments to create multidimensional systems show the potential in the development of miniaturized, high-throughput and automated systems of glycan separation and analysis. Full article

(This article belongs to the Special Issue Monolithic Columns in Separation Sciences)

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