139 research outputs found
ADVANCING THE SEPARATION SCIENCES THROUGH THE DELIVERY OF NEW MATERIALS, TECHNOLOGY AND METHODOLOGY.
A thesis and collection of works submitted to Plymouth University in partial fulfilment for the degree of
DOCTOR OF SCIENC
INVESTIGATION OF CHELATING DYE IMPREGNATED RESINS FOR THE ION CHROMATOGRAPHIC DETERMINATION OF TRACE METALS
A high-performance chelation ion chromatography (HPCIC) system using chelating dye impregnated resins for the determination of trace metals in various complex matrices is
described.
The parameters involved in the production of dye impregnated chelating columns have been
identified and optimised, A range of chelating dyes have been impregnated successfully into
high-performance substrates, producing a number of chelating columns capable of both metal
preconcentration and separations. Each of the chelating columns produced exhibited unique
chelating properties. These columns have been classified in terms of metal retention
characteristics, separation capability and efficiency, dye loading and column capacities.
A number of the above dye impregnated chelating columns have been employed successfully
for the determination of trace metals in various sample types. This includes the determination
of transition and heavy metals in seawater at low ug dm'^ levels, the determination of
aluminium in seawater, the determination of alkaline earth metals in oil-well brines and the
determination of barium and strontium in calcium containing matrices such as mineral waters
and milk powder.Dionex (U.K) Lt
Evaluation of photografted charged sites within polymer monoliths in capillary columns using contactless conductivity detection
Capacitively coupled contactless conductivity detection (C4D) is presented as a novel and versatile means of visualising discrete zones of charged functional groups grafted onto polymer based monoliths. Monoliths were formed within 100 Îźm UV transparent fused silica capillaries and photografting methods were subsequently used to graft a charged functional monomer, 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) onto discrete regions of the âgenericâ monolith using a photomask. Post-modification monolith evaluation involves scanning the C4D detector along the length of the monolith to obtain a profile of the exact spatial location of grafted charged functionalities with millimetre accuracy. The methodology was extended to the visualisation of several zones of immobilised protein (bovine serum albumin) using photografted azlactone groups to enable covalent attachment of the protein to the monolith at precise locations along its length. In addition, the extent of non-specific binding of protein to the ungrafted regions of the monolith due to hydrophobic interactions could be monitored as an increase in background conductivity of the stationary phase. Finally, the technique was cross-validated using fluorescence microscopy by immobilising green fluorescent protein (GFP) in discrete zones and comparing the profiles obtained using both complementary techniques
AuNP-Agglomerated monoliths in pipette tips for lectin affinity extraction of glycoproteins
⢠To in situ fabricate ethylene dimethacrylate porous polymer monoliths within the confines of a commercial 20 ΟL polypropylene pipette tips.
⢠To enhance the monolith surface area by immobilising AuNPs and then functionalise the AuNPs with ECL lectin for selective extraction of galactosylated proteins from complex media
Spiropyran modified microfluidic chip channels for photonically controlled sensor array detection of metal ions
Microfluidic chips are particularly attractive for analytical purposes because they provide a convenient small platform for rapid analysis and detection.1 Furthermore, spiropyrans dyes can be used as photonically controlled, self-indicating molecular recognition agents for the fabrication of sensors.2 Here, we show how through integrating the beneficial characteristics of microfluidic devices and spiropyrans dyes, a simple and very innovative chip for on-line metal ion sensor array can be realised.
The chip (4x3cm) consists of four independent 180m depth, polydimethylsiloxane (PDMS) channels. 1â-(3-Carboxypropyl)-3,3â-dimethyl-6-nitrospiro-[2H-1]-benzopyran-2,2â-indoline is covalently immobilised on the ozone plasma activated PDMS microchannel surfaces.
Upon exposure to UV light, the transparent PDMS channels change to light purple colour because the spiropyran molecules of the surface undergo a heterocyclic ring cleavage that result in the formation of the highly conjugated merocyanine form. When stock solutions of several ion metals (Ca2+,Zn2+,Hg2+,Cu2+) are pumped independently through the four channels, different optical responses were observed for each metal.
1-L.Basabe-Desmonts et al. Anal.Bioanal.Chem.(2008)390:307â315.
2-R.J.Byrne et al. J.Mat.Chem.(2006)16:1332-1337
Gold nano-particle modified silica monolithic micro-columns for selected chromatographic and biological applications.
Monolithic microcolumns and especially silica monoliths are showing several advantages compared to classical particle packed and organic polymeric monolithic columns: ease of production and functionalisation, excellent mechanical and thermal stability. Morphology of the monolithic columns can easily be tuned by simply changing the compositions of reaction mixtures. High porosity and interconnected flow-through pores ensure low back pressures at higher flow rates so increasing reaction speeds. High salt resistance allows use water based buffer solutions without any swelling of the stationary phase, large biomolecules can be utilised and conditions to prevent denaturation and comformation changes of these biomolecules can be maintained.
Introduction of gold nano-particles on the surfaces of silica monoliths allows increase of the surface areas and alows creation of new, exotic surfaces. Gold shows strong affinity towards thiol groups, which can be found in different biomolecules so utilisation of this phenomena would allow production of micro-reactors and bioreactors in order to mimic biological reactions happening in living organisms and large biological systems. Silica monoliths were synthesised using classical sol-gel process. In order to immobilise gold nano-particles, surfaces of the silica monoliths were amminated using standard silanisation reaction with 3-aminopropyl-methyl-diethoxysilane. 20 nm citrate stabilised gold nano-particles were immobilised on the surfaces afterwards. Depending on the desired application, gold nano-oparticle modified silica monoliths were functionalised afterwards. Immobilisation of ionic species such as amino acids and small peptides would allow creation of stationary phase for ion chromatography, retention of enzymes and other biologically active molecules would allow to create micro-reactors. Leaving gold nano-particles unmodified would make ideal stationary phase for micro-extraction.
These modified monoliths were characterised using microscopy techniques, such as scanning electron microscopy (SEM) and field emission SEM. They were used to characterise morphology of the monoliths as well as to evaluate the coverage of the surface with gold nano-particles. The fabricated stationary phases were used for selected biological and chromatographic applications (incorporanting classical chromatographic techniques in order to evaluate the performance of these new modified monolithic materials)
Effect of laser processing parameters and glass type on topology of micro-channels
Traditional processes to manufacture micro-fluidic
devices include standard lithography, electron beam writing
and photo-patterning. These techniques are well established
but most are limited to surface micro-fabrication. Laser
micro-machining provides an alternative for microfabrication
of devices. This paper presents Design of
Experiment models for the fabrication of micro-channel
structures with four different types of glass, soda-lime,
fused-silica, borosilicate and quartz. A 1.5kW CO2 laser
with 90 Îźm spot size was used to fabricate micro-channels
on the surface of glass sheets. Power, P, pulse repetition
frequency, PRF, and translation speed, U, were set as
control parameters. The resulting geometry of the channel
(depth and width) and transmission capabilities were
measured and analyzed. A comparison of the results of this
experimental testing with the four glass types showed that
quartz and fused-silica glasses would have better channel
topologies for chemical sensing applications
Spiropyran modified PDMS micro-fluidic chip device for photonically controlled sensor array detection of metal ions
Microâfluidic chips are particularly attractive in biological and life sciences for analytical purposes
because they provide a convenient small platform for rapid analysis and detection [1]. Using
microâfluidic devices for the determination of ions emerges as a potential solution to some of the
challenges not overtaken by conventional techniques e.g. atomic absorption, inductivelyâcoupled
plasmaâoptical emission, mass spectrometry and ionâselective electrodes [2]. For example, these
devices can integrate complex sample handling processes, calibration, and detection steps into a
compact, portable system. Moreover they require small sample volumes (low Îźl or nl), consume
little power, and are easily constructed for multiâanalyte detection, either through multiple
parallel fluidic architectures or by using arrays of detection elements.
Organic photochromic compounds like spiropyrans are particularly interesting targets for the
development of new approaches to sensing since they offer new routes to multiâfunctional
materials that take advantage of their photoâreversible interconversion between two
thermodynamically stable states (a spiropyran (SP) form, and a merocyanine (MC) form), which
have dramatically different charge, polarity and molecular conformations. Furthermore, they can
be easily incorporated into membranes for improved robustness and ease of handling [3], but
from our perspective, most interesting of all, they have metal ionâbinding and molecular
recognition properties which are only manifested by the MC form. Based on the coordinationinduced
photochromism characteristic of the MC form, spiropyrans have been employed as
molecular probes for metal ions and organic molecules [4].
In this abstract, we show how through integrating the beneficial characteristics of microâfluidic
devices and spiropyrans photoswitches, a simple and very innovative chip configured as an onâline
metal ion sensor array can be realised (Figure 1). The microâfluidic device consists of five
independent 94 Îźm depth, 150 Îźm width channels fabricated in polydimethylsiloxane. The
spiropyran 1ââ(3âcarboxypropyl)â3,3ââdimethylâ6ânitrospiroâ1âbenzopyranâ2,2ââindoline (SPâCOOH)
is immobilised by physical adsorption directly on ozone plasma activated PDMS microâchannel
walls. When the colourless, inactive, spiropyran coating absorbs UV light it switches to the highly
coloured merocyanine form (MCâCOOH), which also has an active binding site for certain metal
ions. Therefore metal ion uptake can be triggered using UV light and subsequently reversed on
demand by shining white light on the coloured complex, which regenerates the inactive spiropyran
form, and releases the metal ion. When stock solutions of several metal ions (Ca2+, Zn2+, Hg2+, Cu2+,
Co2+) are pumped independently through the five channels, different optical responses were
observed for each metal (Figure 2), (i.e. complex formation with metal ions is associated with
characteristic shifts in the visible spectrum), and the platform can therefore be regarded as a
microâstructured device for online multiâcomponent monitoring of metal cations
Immobilisation and incorporation of photochromic spiropyran dyes in polymeric substrates for metal ion sensing and micro-fluidics
In-process phase growth measurement technique in the fabrication of monolithic porous layer open tubular (monoPLOT) columns using capacitively coupled contactless conductivity
A technique for the in-process measurement of polymer stationary phase growth inside fused silica capillaries during the fabrication of monolithic porous layer open tubular (monoPLOT) columns is presented. In this work, capacitively coupled contactless conductivity detection (C4D) was applied as an online measurement tool for porous polymer layer growth within fused silica capillaries. The relationship between effective capillary diameter and C4D response was investigated for two polymers, butyl methacrylateâethylene dimethacrylate (BuMAâEDMA) and polystyreneâdivinylbenzene (PSâDVB) over a range of capillary diameters and layer thicknesses. The described technique can be used with both thermal and photo-initiated approaches for monoPLOT fabrication and provides an accurate, realtime measurement of the porous layer growth within the capillary, which should vastly improve columnto-column reproducibility. The technique was shown to be very precise, with a measured %RSD < 10%
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