Blánaid White

Supermacroporous polyHIPE and cryogel monolithic materials as stationary phases in separation science: a review

With their unique supermacroporous architecture, polyHIPEs (high internal phase emulsions) and cryogels have huge potential as analytical separation stationary phases. Due to their fully interconnected pore structure, mass transfer occurs predominantly via convection, potentially allowing for enhanced chromatographic performance. Additionally their surface functionalities can be tailored by modification of substrates both during and post fabrication. Their surface area is typically lower than comparable particulate stationary phases and problems with their rigidity persist. For these reasons, apart from their applications for large biomolecule analysis, the potential of cryogel and polyHIPE materials as separation phases in separation science have not been extensively realised. However, multiple strategies exist to overcome these limitations, potentially enabling the application of cryogels and polyHIPEs for a diverse range of separations. Current applications, such as chelation resins, which demonstrate the diverse interaction modes of both supermacroporous substrates, and applications of both substrates in analytical separations are considered in this review. Additionally the limitations of these technologies are explored, and strategies to overcome these limitations and further develop these monolithic phases for analytical separations are presented.

Development of a silica monolith modified with Fe3O4 nano‐particles in centrifugal spin column format for the extraction of phosphorylated compounds

In this study, citrate-stabilised iron oxide nano-particles (∼16 nm) have been immobilised on commercial silica monolithic centrifugal spin columns (MonoSpin) for the extraction of phosphorylated compounds. Two alternative strategies were adopted involving either direct electrostatic attachment to an aminated MonoSpin (single-layer method) in the first instance, or the use of a layer-by-layer method with poly(diallyldimethylammonium) chloride. Field-emission scanning electron spectroscopy and energy-dispersive X-ray spectroscopy was used for confirming notably higher coverage of nano-particles using the layer-by-layer method (2.49 ± 0.53 wt%) compared with the single-layer method (0.43 ± 0.30 wt%). The modified monolith was used for the selective separation/extraction of adenosine monophosphate, adenosine diphosphate and adenosine triphosphate with elution using a phosphate buffer. A reversed-phase liquid chromatographic assay was used for confirming that adenosine, as a non-phosphorylated control was not retained on the modified MonoSpin devices, whereas recovery of 80% for adenosine monophosphate, 86% for adenosine diphosphate and 82% for adenosine triphosphate was achieved.

Fabrication of homogenous three dimensionally ordered conducting polymer–polystyrene opal structures in microfluidic channels

A chemical polymerisation method for fabricating an electrochemically addressable, three dimensionally (3-D) ordered homogenous polyaniline (PANI)-based opal structure in a microfluidic channel is described. Electrochemical polymerisation was also explored as a route to creating opal structures of PANI. Interestingly, electrochemical growth resulted in an inhomogeneous gradient-type morphology throughout the depth of the template leading to non-uniform 3-D PANI structures. Using the chemical polymerisation approach, a thin coating of PANI could be deposited homogeneously to the polystyrene (PS) sphere surfaces. This coating was electrochemically accessible subsequent to an electrochemical polymerisation step electrically connecting the channel-based opal structure to an integrated gold working electrode within the microchannel. Electrochemical characterisation of the resultant ordered PANI–PS material in-channel, demonstrated the synthesis of a well behaved, stable PANI coating throughout the PS colloidal crystal (CC) which behaves as a thin film with fast electron transfer.

Development and characterisation of switchable polyaniline-functionalised flow-through capillary monoliths

Polymer monoliths were prepared in capillary format (250 μm i.d.) and used as solid supports for the immobilisation of the conducting polymer polyaniline (PANI). The immobilisation of PANI was confirmed on the large macro-porous structure of a polystyrene–divinylbenzene (PS-co-DVB) monolith. The surface coverage of polyaniline was characterised by field emission scanning electron microscopy (FE-SEM) and by capacitively coupled contactless conductivity detection (C4D), which was operated in scanning mode to non-invasively visualise the axial distribution of the immobilised PANI and to provide information on its doping state. To further demonstrate the successful functionalisation of the monoliths, the PANI-functionalised monoliths were demonstrated as switchable, weak anion-exchange stationary phases as confirmed by studying the retention of iodide using a perchlorate eluent.

Determination of phenolic acids in a range of Irish whiskies, including single pot stills and aged single malts, using capillary electrophoresis with field amplified sample stacking

The aim of this research is to determine the phenolic acids in three types of Irish whiskies, multiple whiskey types from the same distillery, single malt whiskies from the one distillery aged in different casks and a range of single pot still whiskies unique to Ireland, to ascertain the impact on the phenolic acid profile of the aging length, aging process and whiskey mashbill. Whiskey samples were injected directly onto the capillary and preconcentrated using field amplified sample stacking prior to analysis with capillary electrophoresis using ultraviolet detection. It was shown that the phenolic aldehydes vanillin and syringaldehyde increased in concentration with aging, while in whiskies aged in sherry casks, a greater number of phenolic compound types were observed and aging in bourbon casks also resulted in distinctive profiles. It was also shown that single pot still whiskeys contained phenolic compound profiles which were typically rich in phenolic aldehyde concentrations and a diversity of phenolic acids. This is the first time that phenolic acid profiles, which contribute to the beverage flavour, have been characterised for single pot still whiskies.

Polystyrene-co-Divinylbenzene PolyHIPE Monoliths in 1.0 mm Column Formats for Liquid Chromatography

The reversed phase liquid chromatographic (RP-HPLC) separation of small molecules using a polystyrene-co-divinylbenzene (PS-co-DVB) polyHIPE stationary phases housed within 1.0 mm i.d. silcosteel columns is presented within this study. A 90% PS-co-DVB polyHIPE was covalently attached to the walls of the column housing by prior wall modification with 3-(trimethoxysilyl) propyl methacrylate and could withstand operating backpressures in excess of 200 bar at a flow rate of 1.2 mL/min. Permeability studies revealed that the monolith swelled slightly in 100% acetonitrile relative to 100% water but could nevertheless be used to separate five alkylbenzenes using a flow rate of 40 µL/min (linear velocity: 0.57 mm/s). Remarkable column-to-column reproducibility is shown with retention factor variation between 2.6% and 6.1% for two separately prepared columns.

Fabrication of a 3-dimensional nanostructured binary colloidal crystal within a confined channel.

The reproducible fabrication of nanostructured 3Dimensional (3D) binary colloidal crystal (bCC) in a defined geometric space through a simple one step process is detailed. This method allows for the potential fabrication of a bCC in a sealed μchip within a defined area or channel by capillary forces, unlike other bCC formation methods such as dip-drawing, where the substrate must be submerged in a suspension to form a bCC, or bCC monolayers, which are fabricated at the water air interface. Through simple variation in volume fraction ratio (VF(S/L)) of nano-(denoted small, S) and macro-sized (denoted large, L) polystyrene (PS) spheres and diameter size ratio (D(S/L)), the manipulation of bCC structures was also achieved. Variation of nano-sized PS sphere number within the interstitial voids formed between neighbouring macro-sized spheres enabled the reproducible fabrication of LS2 and LS6 structures, which contain 1 and 3 nano-spheres respectively in each interstitial void. It must be noted that while VF(S/L) allows for control of the final LSn structure, thickness of bCC formation in this manner is independent of VFS/L.

Physicochemical properties and phenolic content of honey from different floral origins and from rural versus urban landscapes

The composition of honey influences how beneficial it is to human health. This study evaluated the physiochemical properties and total phenolic content (TPC) of single vs. multi-floral Irish and selected international honeys, and whether properties varied according to hive location. Oilseed rape honey had the lowest TPC of Irish unifloral honeys. Heather honey had the highest TPC, similar to Manuka honey (Mean ± SD = 68.16 ± 2.73 and 62.43 ± 10.03 respectively), and the TPC of ivy honey was approximately half that of heather. Urban multi-floral honeys contained higher TPC (28.26 ± 13.63) than rural honeys (20.32 ± 11.54). Physiochemical properties varied according to floral origin, and whether hives were in urban or rural sites. Irish heather honey had similar physiochemical characteristics to Manuka honey. This first examination of Irish honey confirms that TPC and physiochemical properties vary with honey type and hive location, and suggests that Irish heather honey should be examined for potential health benefits.

Selenised yeast sources differ in their capacity to protect porcine jejunal epithelial cells from cadmium-induced toxicity and oxidised DNA damage

In recent years there has been increasing interest in the use of selenised yeast (Se-Y) as an antioxidant feed supplement. Here, three selenised yeast products are differentiated in terms of bioefficiency and the ameliorative effect on Cadmium (Cd) toxicity in porcine epithelial cells. A porcine digestion in vitro model was chosen to more accurately simulate the bioavailability of different Se-Y preparations, allowing a comprehensive understanding of the bio efficiency of each Se-Y compound in the porcine model. To elucidate a possible mechanism of action of selenium a number of bioassays were applied. Levels of Se dependent antioxidant enzymes (glutathione peroxidase and thioredoxin reductase) were evaluated to analyze the ROS neutralizing capacity of each Se-Y compound. The effects of Se-Y sources on Cd-induced DNA damage and apoptosis-associated DNA fragmentation was assessed using comet and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assays, respectively. Lesion-specific DNA damage analysis and in vitro DNA repair assay determined the DNA repair capacity of each Se-Y source. The results presented in this study confirm that the ability of different commercially available Se-Y preparations to enhance a range of cellular mechanisms that protect porcine gut epithelial cells from Cd-induced damage is concentration-dependent and illustrates the difference in bioefficiency of different Se-Y compounds.