Co-reporter:Ekaterina Nesterenko, Oksana Yavorska, Mirek Macka, Alexander Yavorskyy and Brett Paull
Analytical Methods 2011 vol. 3(Issue 3) pp:537-543
Publication Date(Web):01 Feb 2011
DOI:10.1039/C0AY00649A
Glycidyl methacrylate–ethylene dimethacrylate (GMA-co-EDMA) based monolithic porous layer open tubular (monoPLOT) columns (0.05 mm I.D., monolithic layer thickness ≈ 5 µm) have been fabricated using an automated column scanning technique, providing UV polymerisation at 365 nm. Columns were chemically modified to obtain desired diol groups on the surface, and the longitudinal homogeneity of the stationary phase was profiled using scanning capacitively coupled contactless conductivity detector (sC4D), before and after such modification. Using the automated scanning polymerisation technique, column-to-column production reproducibility, including longitudinal phase thickness, was within ±5% RSD. The prepared columns were tested to evaluate their liquid chromatographic stationary phase selectivity, efficiency and reproducibility, with a series of test protein mixtures. Under optimised gradient conditions, the separation of up to 8 proteins was demonstrated on the open tubular column (510 × 0.05 mm I.D.), with a column pressure drop of <1.5 MPa.
Co-reporter:Hassan Alwael, Damian Connolly and Brett Paull
Analytical Methods 2011 vol. 3(Issue 1) pp:62-69
Publication Date(Web):25 Nov 2010
DOI:10.1039/C0AY00516A
A solid phase extraction, liquid chromatography and fluorescence (SPE-RPLC-FL) based protocol for the determination of free monosaccharides in highly complex raw material powders and formulated fermentation feedstocks and broths has been developed. Monosaccharides within sample extracts were derivatised pre-column with anthranilic acid and the derivatives separated using reversed-phase LC with fluorescence detection. Using a 2.1 mm × 50 mm 1.8 µm Zorbax Eclipse XDB-C18 column, a flow rate of 0.4 mL min−1 and an acetonitrile gradient in a sodium acetate buffer (pH 4.3; 50 mmol L−1) the baseline resolution of glucosamine, mannosamine, galactosamine, galactose, mannose, glucose, ribose, xylose, fucose and sialic acid within 20 minutes was achieved. Pre-column derivatisation involved combining a 30 mg mL−1 solution of anthranilic acid in a 1:1 ratio with an aqueous standard prior to injection. Standard analytical performance criteria were used for evaluation purposes, with the method found to exhibit LOD's as low as 10 fmol, and be linear and precise (%RSD < 2.2% (n = 7). The method was applied to the analysis of a range of highly complex biopharmaceutical production samples, including yeastolate powders, chemically defined media and in-process fermentation broth samples. Sample preparation involved passing an aqueous sample through a C18 solid phase extraction cartridge to trap hydrophobic peptides and vitamins, with recovery of all test sugars exceeding 90%. Finally, standard statistical analysis was performed on samples taken from different lots in order to estimate lot-to-lot variability.
Co-reporter:Mercedes Vázquez, Brett Paull
Analytica Chimica Acta 2010 Volume 668(Issue 2) pp:100-113
Publication Date(Web):4 June 2010
DOI:10.1016/j.aca.2010.04.033
This review critically summarises recent novel and advanced achievements in the application of monolithic materials and related porous polymer gels in micro-fluidic devices appearing within the literature over the period of the last 5 years (2005–2010). The range of monolithic materials has developed rapidly over the past decade, with a diverse and highly versatile class of materials now available, with each exhibiting distinct porosities, pore sizes, and a wide variety of surface functionalities. A major advantage of these materials is their ease of preparation in micro-fluidic channels by in situ polymerisation, leading to monolithic materials being increasingly utilised for a larger variety of purposes in micro-fluidic platforms. Applications of porous polymer monoliths, silica-based monoliths and related homogeneous porous polymer gels in the preparation of separation columns, ion-permeable membranes, preconcentrators, extractors, electrospray emitters, micro-valves, electrokinetic pumps, micro-reactors and micro-mixers in micro-fluidic devices are discussed herein. Procedures used in the preparation of monolithic materials in micro-channels, as well as some practical aspects of the micro-fluidic chip fabrication are addressed. Recent analytical/bioanalytical and catalytic applications of the final micro-fluidic devices incorporating monolithic materials are also reviewed.
Co-reporter:Hassan Alwael, Damian Connolly, Leon Barron, Brett Paull
Journal of Chromatography A 2010 Volume 1217(Issue 24) pp:3863-3870
Publication Date(Web):11 June 2010
DOI:10.1016/j.chroma.2010.04.036
Two rapid, sensitive and quantitative methods for the determination of the cysteine and cystine ratio in complex defined media feedstock using monolithic reversed-phase liquid chromatography (RPLC) and RPLC–MS are presented. Cysteine is pre-derivatised with purified 2-chloro-1-methylquinolinium tetrafluoroborate (CMQT) and separated from other derivatisation products on a narrow-bore 50 mm × 2 mm I.D. monolithic C18 column with UV detection at 355 nm. For reversed-phase LC (RPLC) the separation is carried out isocratically using a mobile phase of 50 mM trichloroacetic acid (TCA) adjusted to pH 2.5 with lithium hydroxide (LiOH) and acetonitrile (83:14) pumped at 1.5 mL/min with an elevated column temperature. For RPLC–MS an ammonium acetate and acetonitrile gradient method was developed with a reduced flow rate of 0.3 mL/min. The treatment of the samples consisted of dividing them into two aliquots, the first aliquot is analysed for cysteine and the second aliquot is analysed for cystine after its quantitative reduction to cysteine using tris(2-carboxyethyl)phosphine (TCEP). Both methods are linear, with R2 > 0.999 for 0.25–500 μM for cysteine and 0.25–250 μM for cystine using the LC–UV method, sensitive, with detection limit of 36 nM for cysteine, and precise, with ≤1.1% RSD for both retention time and peak area (n = 6). Samples (n = 31) of an industry standard and supplied chemically defined media feedstock were analysed, finding cysteine ranging from 1.56 to 2.26 μg/mL and cystine from 1062.02 to 1348.13 μg/mL.
Co-reporter:Ekaterina P. Nesterenko, Pavel N. Nesterenko, Damian Connolly, Flavie Lacroix, Brett Paull
Journal of Chromatography A 2010 Volume 1217(Issue 14) pp:2138-2146
Publication Date(Web):2 April 2010
DOI:10.1016/j.chroma.2010.02.007
A new method for the fixation of polymethacrylate monoliths within titanium tubing of up to 0.8 mm I.D. for use as a chromatographic column under elevated temperatures and pressures is described. The preparation of butyl methacrylate–ethylene dimethacrylate-based monolithic stationary phases with desired porous structures was achieved within titanium tubing with pre-oxidised internal walls. The oxidised titanium surface was subsequently silanised with 3-trimethoxysilylpropyl methacrylate resulting in tight bonding of butyl methacrylate porous monolith to the internal walls, providing stationary phase stability at column temperatures up to 110 °C and at operating column pressure drops of >28 MPa. The titanium housed monoliths exhibited a uniform and dense porous structure, which provided peak efficiencies of up to 59,000 theoretical plates per meter when evaluated for the separation of small molecules in reversed-phase mode, under optimal conditions (achieved at 15 μL/min and temperature of 110 °C for naphthalene with a retention factor, k = 0.58). The developed column was applied to the reversed-phase isocratic separation of a text mixture of pesticides.
Co-reporter:Sinead Currivan;Damian Connolly;Eoin Gillespie
Journal of Separation Science 2010 Volume 33( Issue 4-5) pp:484-492
Publication Date(Web):
DOI:10.1002/jssc.200900720
Abstract
Polymeric monoliths in capillary formats have been fabricated incorporating a gradient of charged functional groups along their length. Scanning capacitively coupled contactless conductivity detection (sC4D) was then used to measure the conductive response of the stationary phase and characterise the relative axial distribution of functional groups along the column length. Gradients of 2-acrylamido-2-methyl-1-propanesulphonic acid were prepared using either photografting methods or by filling a capillary column with segmented plugs of monomer mixtures each containing incrementally higher concentrations of the functional monomer. The utility of sC4D as a rapid and non-invasive tool for assessing the slope of a variety of gradient configurations is demonstrated. Repeatability of the sC4D measurements was <1.7% RSD. Columns with a gradient of covalently bonded iminodiacetic acid were also produced. Changes in the gradient slope were observed after chelation of copper on the stationary phase via a reduction of the conductive response. The effect upon the observed gradient profile of changing the co-monomer composition during column fabrication was studied.
Co-reporter:Ali H. Eltmimi;Leon Barron;Aran Rafferty;John P. Hanrahan;Olga Fedyanina;Ekaterina Nesterenko;Pavel N. Nesterenko
Journal of Separation Science 2010 Volume 33( Issue 9) pp:1231-1243
Publication Date(Web):
DOI:10.1002/jssc.200900845
Abstract
A range of porous carbon-based monolithic (PCM) rods with flow-through pore sizes of 1, 2, 5 and 10 μm, were produced using a silica particle template method. The rods were characterised using SEM and energy-dispersive X-ray spectroscopy, BET surface area and porous structure analysis, dilatometry and thermal gravimetry. SEM evaluation of the carbon monolithic structures revealed an interconnected rigid bimodal porous structure and energy-dispersive X-ray spectroscopy analysis verified the quantitative removal of the embedded silica beads. The specific surface areas of the 1, 2, 5 and 10 μm rods were 178, 154, 84 and 125 m2/g after pyrolysis and silica removal, respectively. Shrinkage of the monolithic rods during pyrolysis is proportional to the particle size of the silica used and ranged from 9 to 12%. Mercury porosimetry showed a narrow distribution of pore sizes, with an average of ∼700 nm for the 1 μm carbon monolith. The suitability of bare and surface oxidised PCM rods for the use as a stationary phase for reversed and normal phase LC was explored. The additional modification of PCM rods with gold micro-particles followed by 6-mercaptohexanoic acid was performed and ion-exchange properties were evaluated.
Co-reporter:Ekaterina P. Nesterenko, Pavel N. Nesterenko, Brett Paull
Analytica Chimica Acta 2009 Volume 652(1–2) pp:3-21
Publication Date(Web):12 October 2009
DOI:10.1016/j.aca.2009.06.010
Significant advances within the field of ion chromatography (IC) have often had their roots in research focussed on the development of new phase technologies, aimed to both simultaneously increase efficiency and vary selectivity. To increase selectivity it is necessary to develop new selective ion-exchangers, achieved by varying the nature of functional groups and the matrix of the stationary phase. In this comprehensive review, developments over the past decade in the production and application of zwitterionic and amphoteric ion-exchangers are presented and discussed. Zwitterionic and amphoteric ion-exchangers, where positive and negative charges are located in close proximity, exhibit alternative ion selectivity to standard anion and cation ion-exchangers, such as those traditionally used in IC, and have the potential for selectivity optimisation in IC due to control of the ratio of electrostatic attraction/repulsion forces between analyte ions and ion-exchange groups. This can result in the ability to utilise relatively dilute eluents, which increases detector sensitivity, with further advantages of zwitterionic ion-exchangers including their possible application to the simultaneous separation of cationic and anionic species.
Co-reporter:Eoin Gillespie, Damian Connolly and Brett Paull
Analyst 2009 vol. 134(Issue 7) pp:1314-1321
Publication Date(Web):03 Apr 2009
DOI:10.1039/B901300H
Capacitively coupled contactless conductivity detection (C4D) is utilised as a simple, rapid and non-invasive technique for the quantitative evaluation of the ion-exchange capacity of charged polymer monoliths in capillary format. A charged monomer, 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) was photografted onto a 100 µm i.d. butyl methacrylate-co-ethylenedimethacrylate monolith in a number of discrete 10 mm zones. By varying the energy dose (J/cm2) during grafting of each zone, the grafting density and thus ion-exchange capacity could be precisely controlled. Ion-exchange capacity could be correlated with energy dose by measuring the conductive response of each grafted region using scanning C4D techniques. Repeatability of the scanning C4D method was excellent with % RSD values of 0.7% and 2.4% obtained for three replicate scans of the ungrafted and grafted regions of a single monolith, respectively. Repeatability of the photografting process on separate monoliths was also examined by comparison of C4D profiles. The spatial accuracy of photografting was probed using scanning C4D which could measure the conductive response of the monolith at measurement intervals as low as 1 mm along its entire length. Scanning C4D was also used for the real time visualisation of the equilibration of grafted zones to permit the optimisation of monolith washing procedures. Finally, scanning C4D was applied to the measurement of the ion-exchange capacity of butyl methacrylate-co-AMPS-co-ethylenedimethacrylate copolymers with a direct correlation between monolith conductive response and concentration of charged monomer in the polymerisation mixture. The longitudinal homogeneity of charge along the monolith was 0.3% RSD, demonstrating that the charged functional monomer was evenly dispersed throughout the bulk of the monolith. Ion-exchange capacity was cross validated chromatographically using breakthrough studies and found to closely correlate to within 1% of the measurements made by scanning C4D.
Co-reporter:Eoin Gillespie;Damian Connolly;Pavel N. Nesterenko
Journal of Separation Science 2009 Volume 32( Issue 15-16) pp:2659-2667
Publication Date(Web):
DOI:10.1002/jssc.200900232
Abstract
The application of scanning capacitively coupled contactless conductivity detection (SC4D) for the determination of pH dependant behaviour of two aminopolycarboxylates immobilised onto the surface of a monolithic capillary column is described. The use of SC4D to visualise changes in conductivity of the discrete zones of functional groups within monolithic capillary columns allows for the effects of immobilisation on the physicochemical properties of zones to be compared to that of the functional group in solution. The perturbation of the pKa values of the functional groups can be attributed to the change in chemical environment experienced by the functional group through the presence of local hydrogen bonding and surface induced effects. These bonds, both between adjacent functional groups and with the monolithic polymethacrylate scaffold, result in a modification of the electron density on the functional group and therefore a change in pKa. Changes in the pKa of N-(2-acetamido)iminodiacetic acid (ADA) from 2.48 to 5.2 for one of the acidic protons, with little change in the pKa of the amine group, were observed, which correlates to similar changes in aggregated systems of aminopolycarboxylates. Similar results were obtained for the iminodiacetic acid (IDA) once immobilised onto the surface of the monolith. Furthermore, the ability to measure changes in the charge of such discrete zones of functional groups allows for the visualisation of complexation events occurring directly on-column, where such complexes result in a change in charge of the functional group. This potentially useful technique is illustrated within for the formation of aminopolycarboxylate complexes with a selection of metal ions.
Co-reporter:Damian Connolly
Journal of Separation Science 2009 Volume 32( Issue 15-16) pp:2653-2658
Publication Date(Web):
DOI:10.1002/jssc.200900229
Abstract
A glycidyl methacrylate-co-ethylene dimethacrylate monolith in capillary format (100 μm/id) has been grafted with chains of poly([2(methacryloyloxy)ethyl] trimethylammonium chloride (poly-META) and applied to the ion-chromatographic separation of selected inorganic anions. Grafting chains of META onto the generic monolithic scaffold resulted in a monolith with ‘electrolyte responsive flow permeability’, which manifested as increased permeability in the presence of electrolyte solutions. Using an eluent of 2 mM sodium benzoate and on-column contactless conductivity detection, a test mixture of six common anions was isocratically separated and detected within 12 min, with the first four anions baseline resolved within a retention time window of 3.2 min. Retention time precision was ⪇1.2% for all anions tested. Separation efficiencies of 15 000 N/m were achieved for fluoride at 1 μL/min, with column efficiencies up to 29 500 N/m obtained at a lower flow rate of 100 nL/min. Furthermore, repeatability of the column modification procedure using photografting methods was acceptable, with retention times between replicate columns matching within 9%.
Co-reporter:Fernando Benito-Lopez, Silvia Scarmagnani, Zarah Walsh, Brett Paull, Mirek Macka, Dermot Diamond
Sensors and Actuators B: Chemical 2009 Volume 140(Issue 1) pp:295-303
Publication Date(Web):18 June 2009
DOI:10.1016/j.snb.2009.03.080
In this paper, we show how through integrating the beneficial characteristics of micro-fluidic devices and spiropyrans dyes, a simple and very innovative chip configured as an on-line photonically controlled self-indicating system for metal ion accumulation and release can be realised. The micro-fluidic device consists of five independent 94 μm depth, 150 μm width channels fabricated in polydimethylsiloxane. The spiropyran 1′-(3-carboxypropyl)-3,3′-dimethyl-6-nitrospiro-1-benzopyran-2,2′-indoline is immobilised by physical adsorption into a polydimethylsiloxane matrix and covalently on the ozone plasma activated polydimethylsiloxane micro-channel walls. When the colourless, inactive, spiropyran coating absorbs UV light it switches to the highly coloured merocyanine form, 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, and the platform can therefore be regarded as a micro-structured device for photo-controlled self-indicating metal ion complexation, accumulation and release.
Co-reporter:Leon Barron, Martina O’Toole, Dermot Diamond, Pavel N. Nesterenko, Brett Paull
Journal of Chromatography A 2008 Volume 1213(Issue 1) pp:31-36
Publication Date(Web):5 December 2008
DOI:10.1016/j.chroma.2008.08.049
The selectivity, retention and separation of transition metals on a short (2 mm × 50 mm) column packed with a poly-iminodiacetic acid functionalised polymer 10 μm resin (Dionex ProPac IMAC-10®) are presented. This stationary phase, typically used for the separation of proteins, is composed of long chain poly-iminodiacetic acid groups grafted to a hydrophilic layer surrounding a 10 μm polymeric bead. Through the use of a combination of a multi-step pH and picolinic acid gradient, the separation of magnesium, iron, cobalt, cadmium, zinc, lead and copper was possible, followed by post-column reaction with 4-(2-pyridylazo) resorcinol (PAR) and absorbance detection at 510 nm using a novel and inexpensive optical detector, comprised of two light emitting diodes with one acting as a light source and the other as a detector. Column efficiency for selective transition metals was in excess of N = 10,000, with the baseline separation of seven metal cations in <3 min possible under optimised conditions. Detection limits of between 5 and 81 μg/L were possible based upon a 50 μL injection volume.
Co-reporter:Ekaterina P. Nesterenko, Pavel N. Nesterenko, Brett Paull
Journal of Chromatography A 2008 Volume 1213(Issue 1) pp:62-69
Publication Date(Web):5 December 2008
DOI:10.1016/j.chroma.2008.08.096
The retention and separation selectivity of inorganic anions and on-column derivatised negatively charged citrate or oxalate metal complexes on reversed-phase stationary phases dynamically coated with N-(dodecyl-N,N-dimethylammonio)undecanoate (DDMAU) has been investigated. The retention mechanism for the metal–citrate complexes was predominantly anion exchange, although the amphoteric/zwitterionic nature of the stationary phase coating undoubtedly also contributed to the unusual separation selectivity shown. A mixture of 10 inorganic anions and metal cations was achieved using a 20 cm monolithic DDMAU modified column and a 1 mM citrate eluent, pH 4.0, flow rate equal to 0.8 mL/min. Selectivity was found to be strongly pH dependent, allowing additional scope for manipulation of solute retention, and thus application to complex samples. This is illustrated with the analysis of an acidic mine drainage sample with a range of inorganic anions and transition metal cations, varying significantly in their concentrations levels.
Co-reporter:Ekaterina P. Nesterenko, Pavel N. Nesterenko, Brett Paull
Journal of Chromatography A 2008 Volume 1178(1–2) pp:60-70
Publication Date(Web):18 January 2008
DOI:10.1016/j.chroma.2007.11.038
Short reversed-phase columns (50 mm × 4.6 mm Gemini C18) were dynamically coated with carboxybetaines of the general structure, C12H25N+(CH3)2(CH2)nCOOH, namely (N-dodecyl-N,N-dimethylammonio)undecanoate, DDMAU (n = 10) and (N-dodecyl-N,N-dimethylammonio)butyrate, DDMAB (n = 3), and investigated for the separation of inorganic anions in ion chromatography. The role of the ionic strength of coating surfactant solutions on their adsorption and resultant column capacity was studied. The retention of inorganic anions was investigated with different eluents at various concentrations and pH. Interestingly, no retention for anions was found with pure water as the eluent, but the addition of small amounts of electrolytes, up to 0.1 mM, caused a sharp increase in the retention of analytes. The effect of increasing anion retention with an increase in eluent cation charge was also observed. Based on this effect a new cation charge gradient concept was proposed and applied to the separation of a standard mixture of anions.
Co-reporter:Eoin Gillespie, Damian Connolly, Pavel N. Nesterenko and Brett Paull
Analyst 2008 vol. 133(Issue 7) pp:874-876
Publication Date(Web):03 Apr 2008
DOI:10.1039/B803349H
The use of on-column capacitively coupled contactless conductivity detection for the accurate non-invasive visualisation of the pH dependence of covalently bound boronic acid groups within a monolithic polymeric capillary column is demonstrated.
Co-reporter:Jonathan Bones, Cepta Duffy, Mirek Macka and Brett Paull
Analyst 2008 vol. 133(Issue 2) pp:180-183
Publication Date(Web):17 Dec 2007
DOI:10.1039/B714807K
Up to ten individual reversed-phase monolithic LC columns were efficiently coupled to equal a total column length of 1 m. The column generated up to 90000 theoretical plates under optimum conditions with a peak capacity under gradient conditions of 244 peaks h−1 at a total column backpressure of just 140 bar, directly coupled to ESI-MS.
Co-reporter:Wasim Bashir, Frank McGovern, Phillip O'Brien, Margaret Ryan, Liam Burke and Brett Paull
Environmental Science: Nano 2008 vol. 10(Issue 6) pp:730-738
Publication Date(Web):16 May 2008
DOI:10.1039/B803010C
A major Irish study, based upon more than 8000 samples collected over the measurement period of 22 years, for sulfur dioxide (SO2–S), sulfate (SO4–S) and nitrogen dioxide (NO2–N) concentrations (μg m−3) within air, and the ionic composition of precipitation samples based on sodium (Na+), potassium (K+), magnesium (Mg2+), calcium (Ca2+), chloride (Cl−), sulfate (SO4–S), non-sea salt sulfate (nssSO4–S), ammonium (NH4–N), and nitrate (NO3–N) weighted mean concentrations (mg l−1), has been completed. For the air samples, the sulfur dioxide and sulfate concentrations decreased over the sampling period (1980–2004) by 75% and 45%, respectively, whereas no significant trend was observed for nitrogen dioxide. The highest concentrations for sulfur dioxide, sulfate and nitrogen dioxide were associated with wind originating from the easterly and northeasterly directions i.e. those influenced by Irish and European sources. The lowest concentrations were associated with the westerly directions i.e. for air masses originating in the North Atlantic region. This was further verified with the use of backward (back) trajectory analysis, which allowed tracing the movement of air parcels using the European Centre for Medium range Weather Forecasting (ECMWF) ERA-40 re-analysis data. High non-sea salt sulfate levels were being associated with air masses originating from Europe (easterlies) with lower levels from the Atlantic (westerlies). With the precipitation data, analysis of the non-sea salt sulfate concentrations showed a decrease by 47% since the measurements commenced.
Co-reporter:Leon Barron, John Tobin and Brett Paull
Environmental Science: Nano 2008 vol. 10(Issue 3) pp:353-361
Publication Date(Web):18 Feb 2008
DOI:10.1039/B717453E
An analytical method to determine a selection of 27 frequently prescribed and consumed pharmaceuticals in biosolid enriched soils and digested sludges is presented. Using a combination of pressurized liquid extraction, solid phase extraction and liquid chromatography with tandem mass spectrometry, it was possible to detect all analytes in each sample type at the low-sub ng g−1 level. Solid phase extraction efficiencies were compared for 6 different sorbent types and it was found that Waters Oasis HLB cartridges offered enhanced selectivities with 20 analytes showing final method recoveries ≥60% in both soils and digested sludges. The method was validated for linearity, range, precision and limits of detection in both sample matrices. All analytes were then determined in sludge enriched soils as well as the precursor thermally dried sludge fertilizer produced from a primary wastewater treatment plant. Levels of the antibacterial agent triclosan were found to exceed 20 μg g−1 in digested sludge and 5 μg g−1 in thermally dried sludge cake. Significant traces of carbamazepine and warfarin were also detected in the above samples.
Co-reporter:Fu-Qiang Nie, Mirek Macka and Brett Paull
Lab on a Chip 2007 vol. 7(Issue 11) pp:1597-1599
Publication Date(Web):02 Aug 2007
DOI:10.1039/B707773B
A micro-fluidic chip, within which two monolithic electroosmotic pumps are utilised for sample preconcentration, injection and delivery is presented. The monolithic pumps were capable of producing stable and bubble free flow rates at applied voltages below 2 kV, with a current <10 µA. Electrokinetic (EK) sample injection, down to low nano-litre volumes, was quantitatively controlled through applied voltage and injection times, whilst the sample pump delivered a carrier solution to indirectly dispense the sample. A nano-flow sensor (NFS) was used to continuously monitor the flow rate stability of each pump, showing response times of <5–10 s for changes in applied voltage. A capacitively coupled contactless conductivity detector (C4D), as an off-chip on-capillary detector, was used to complete the micro-flow injection analysis (FIA) system. A monolithic electroosmotic pump (EOP), modified with an anionic surfactant, was used to demonstrate a novel approach to on-chip cation preconcentration and elution.
Co-reporter:Eoin Gillespie, Damian Connolly, Miroslav Macka, Pavel N. Nesterenko and Brett Paull
Analyst 2007 vol. 132(Issue 12) pp:1238-1245
Publication Date(Web):02 Oct 2007
DOI:10.1039/B711350A
A capacitively-coupled contactless conductivity detector (C4D) has been utilised as an on-capillary detector within a capillary ion chromatograph, incorporating a reversed-phase monolithic silica capillary column semi-permanently modified with a suitable ionic surfactant. The monolithic capillary column (150 × 0.1 mm i.d.) was modified using sodium dioctyl sulfosuccinate (DOSS), an anionic surfactant, for the separation of small inorganic and organic cations. With the use of the on-capillary conductivity detector, the longitudinal homogeneity and temporal stability of the coating were investigated. The approach allowed a detailed non-invasive observation of the nature of the ion-exchange coating over time, and an example of an application of the technique to produce a longitudinal stationary-phase charge gradient is shown. An investigation of the basis of the measured on-capillary conductivity was carried out with a counter ion study, clearly showing the on-capillary detection technique could also distinguish between chemical forms of the immobilised ion exchanger. The above method was used to produce a stable and homogeneously-modified monolithic ion-exchange capillary column, for application to the separation of inorganic alkaline earth cations and amino acids.
Co-reporter:Fu-Qiang Nie, Mirek Macka, Leon Barron, Damian Connolly, Nigel Kent and Brett Paull
Analyst 2007 vol. 132(Issue 5) pp:417-424
Publication Date(Web):07 Mar 2007
DOI:10.1039/B618386G
A robust, compact, on-chip, electro-osmotic micro-pump (EOP) for micro-flow analysis, based on parallel, encased, 10 × 0.1 mm I.D. monolithic silica capillary columns has been developed. A 15 × 40 × 2 mm poly(methyl methacrylate) (PMMA) chip, containing a total of nine parallel EOP systems was fabricated, allowing the use of single, double or triple monolithic columns to produce increased flow as required. The monolithic silica was compatible with both aqueous and organic solvents without swelling or shrinking problems, with the triple column EOP capable of generating flow of up to 0.6 μL min−1 under zero pressure load and over 0.1 μL min−1 with an applied pressure of ca. 2.4 bar using an applied voltage of just 2 kV. Current generated at the 2 kV applied voltage for a 2 mM acetate buffer solution (pH 4.5) was under 4 μA, allowing stable, bubble-free flow. The developed triple column EOP was incorporated within a micro-fluidic chip (5.0 × 2.0 × 0.4 cm) integrated with a second single 10 × 0.1 mm column EOP, for combined sample injection and simple on-chip micro-flow analysis.
Co-reporter:Jonathan Bones, Mirek Macka and Brett Paull
Analyst 2007 vol. 132(Issue 3) pp:208-217
Publication Date(Web):08 Jan 2007
DOI:10.1039/B615669J
A study comparing recently available 100 × 3 mm id, 200 × 3 mm id monolithic reversed-phasecolumns with a 50 × 2.1 mm id, 1.8 µm particle packed reversed-phasecolumns was carried out to determine the most efficient approach (using traditional van Deemter analysis and a modern kinetic plot approach) for the rapid screening of samples for 16 illicit drugs and associated metabolites. A plot of column backpressure versusplate number (N) showed a significant advantage of using the monolithic phases, with the 20 cm monolithic column exhibiting a maximum 15000 plates at a column backpressure of ≈70 bar, compared to ≈7000 plates at 150 bar for the 5 cm 1.8 µm particle packed column. Optimum linear velocities were found to be 0.40 mm s–1, 0.52 mm s–1 and 0.98 mm s–1 for the three above columns, respectively. The 20 cm monolithic column was subsequently applied to the separation and determination of illicit drug contamination on Irish euro banknotes, using methanol extraction followed by LC-MS/MS. Method performance data showed that the new LC-MS/MS method was significantly more sensitive than previous GC-MS/MS based methods for this application, with detection limits in the pg note–1 region, based upon a 20 µL standard injection. All of the notes examined tested positive for trace quantities of cocaine, with benzoylecgonine detected on 12 of the 45 notes sampled. Traces of heroin were also detected on three of the 45 notes.
Co-reporter:Colmán Ó Ríordáin, Eoin Gillespie, Damian Connolly, Pavel N. Nesterenko, Brett Paull
Journal of Chromatography A 2007 Volume 1142(Issue 2) pp:185-193
Publication Date(Web):23 February 2007
DOI:10.1016/j.chroma.2006.12.049
A reversed-phase monolithic silica based capillary column (Onyx C18, 150 mm × 0.1 mm) was modified with the amphoteric surfactant, N-dodecyl-N,N-(dimethylammonio)undecanoate (DDMAU) and evaluated for the separation and determination of inorganic anions using on-column capacitively coupled contactless conductivity detection (C4D). The chromatographic performance of the column was evaluated and under optimal conditions separation efficiencies of 56,200 plates per meter or 7025 plates per column (at detection point) were observed (for iodide). Direct plumbing of the capillary column to the micro-injector and on-column detection eliminated extra-column band broadening, thus allowing accurate analysis of van Deemter curves obtained for the monolithic capillary column. The calculated value for the C-term in the obtained van Deemter curve was between 3 and 4 ms for inorganic anions, allowing for the utilisation of relatively high flow rates without significant losses in efficiency. The performance of the C4D detector was investigated and compared for detection on an open tubular capillary column and on the modified monolithic silica capillary column. The on-column detection approach did not result in any significant decrease in peak sensitivity for the monolith compared to responses recorded for open tubular capillary columns, and in addition meant the system could be applied to rapid separations by simple variation in apparent column length. The proposed chromatographic system allowed for detection of common anions at sub-ppm level with a 10 nL injection volume. Additionally, on-column detection allowed visualisation of the development of the separation at any point in time and evaluation of the longitudinal uniformity of the ion-exchange coating.
Co-reporter:Cepta Duffy;Ekaterina P. Nesterenko;Céline Guivarc'h
Journal of Separation Science 2007 Volume 30(Issue 17) pp:2910-2916
Publication Date(Web):31 OCT 2007
DOI:10.1002/jssc.200700355
An RP monolithic column coated with an amphoteric carboxybetaine type surfactant has been used with a combined triple eluent concentration, pH and flow gradient ion chromatography technique for the simultaneous separation of up to 18 nucleotides, nucleosides and nucleobases. The separation of up to eight precursors on a 1 cm long monolithic microcolumn using the combined gradient approach is also shown. The method was applied to the separation of the above nucleic acid precursors in perchloric acid extracts of yeastolates samples.
Co-reporter:Vincent O'Shea;Paul Clark;Brendan O'Connor;Damian Connolly
Journal of Separation Science 2007 Volume 30(Issue 17) pp:3060-3068
Publication Date(Web):31 OCT 2007
DOI:10.1002/jssc.200700365
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 first formed within 100 μm UV-transparent fused silica capillaries. Photografting methods were subsequently used to graft a charged functional monomer, 2-acrylamido-2-methyl-1-propanesulfonic acid, onto discrete regions of the 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 digital photography in combination with a UV light source by immobilising green fluorescent protein in discrete zones and comparing the results obtained using both complementary techniques.
Co-reporter:Jonathan Bones, Kevin V. Thomas and Brett Paull
Environmental Science: Nano 2007 vol. 9(Issue 7) pp:701-707
Publication Date(Web):17 May 2007
DOI:10.1039/B702799K
A solid phase extraction (SPE) method has been developed and applied in conjunction with a previously reported liquid chromatography tandem mass spectrometry (LC–MS–MS) procedure for the determination of illicit drugs and abused pharmaceuticals in treated wastewater and surface water samples at the ng L−1 level. A full method validation was also performed and determined levels of analytical sensitivity were found to lie in the 1–10 ng L−1 range using river water as a test sample matrix and a sample size of 500 mL. The developed procedure was successfully applied for the determination of the chosen analytes in wastewater treatment plants in Dublin, Ireland and rapidly expanding commuter towns in the surrounding counties. Cocaine was detected in 70% of the collected samples in the range of 25–489 ng L−1, its primary metabolite, benzoylecognine (BZE) was also detected in the range of 22–290 ng L−1. Other substances detected included morphine, Tempazepam and the primary metabolite of methadone.
Co-reporter:Leon Barron, Pavel N. Nesterenko, Dermot Diamond, Martina O’Toole, King Tong Lau, Brett Paull
Analytica Chimica Acta 2006 Volume 577(Issue 1) pp:32-37
Publication Date(Web):1 September 2006
DOI:10.1016/j.aca.2006.05.101
The use of a low pressure ion chromatograph based upon short (25 mm × 4.6 mm) surfactant coated monolithic columns and a low cost paired emitter–detector diode (PEDD) based detector, for the determination of alkaline earth metals in aqueous matrices is presented. The system was applied to the separation of magnesium, calcium, strontium and barium in less than 7 min using a 0.15 M KCl mobile phase at pH 3, with post-column reaction detection at 570 nm using o-cresolphthalein complexone. A comparison of the performance of the PEDD detector with a standard laboratory absorbance detector is shown, with limits of detection for magnesium and calcium using the low cost PEDD detector equal to 0.16 and 0.23 mg L−1, respectively. Finally, the developed system was used for the determination of calcium and magnesium in a commercial spring water sample.
Co-reporter:Jonathan Bones, Kevin V. Thomas, Brett Paull
Journal of Chromatography A 2006 Volume 1132(1–2) pp:157-164
Publication Date(Web):3 November 2006
DOI:10.1016/j.chroma.2006.07.068
A method has been developed for the determination of zinc pyrithione (ZnPT) in environmental water samples using monolithic reversed-phase silica columns for rapid on-line large volume solid phase extraction in tandem with on-line matrix removal using sacrificial strong anion exchange (SAX) columns. This is coupled with reversed-phase liquid chromatography with atmospheric pressure chemical ionisation mass spectrometric detection. Limits of detection in spiked river water samples, using a 200 mL preconcentration volume, were determined as 18 ng L−1, with a limit of quantitation of 62 ng L−1. The percentage recovery from spiked river water was found to be 72 ± 9 (n = 3 extractions), whilst overall method precision, following 10 repeat complete analyses was found to be 27% RSD at 1 μg L−1. Linearity was determined over the concentration range of 0.25–10 μg L−1 and the calculated regression coefficient was R2 = 0.9802. The method was used to investigate the environmental fate of zinc pyrithione in waters and its partition coefficient between sediment and water phases.
Co-reporter:Colmán Ó Ríordáin, Leon Barron, Ekaterina Nesterenko, Pavel N. Nesterenko, Brett Paull
Journal of Chromatography A 2006 Volume 1109(Issue 1) pp:111-119
Publication Date(Web):17 March 2006
DOI:10.1016/j.chroma.2006.01.002
The rapid separation of inorganic anions on short monolithic columns permanently coated with a long chained zwitterionic carboxybetaine-type surfactant is shown. The surfactant, N-dodecyl-N,N-(dimethylammonio)undecanoate (DDMAU), was used to coat 2.5, 5.0 and 10 cm long reversed-phase silica monoliths, resulting in a permanent zwitterionic exchange surface when used with aqueous based eluents. The unique structure of the surfactant results in a charge double layer structure on the surface of the stationary phase, with strong internal anionic and weak external cationic exchange groups. The dissociation of the weak external carboxylic acid group acts to shield the inner anionic exchange site, resulting in substantial effective capacity changes with eluent pH. Utilising this effect with the application of an eluent pH gradient, simultaneously combined with eluent flow-rate gradients, very rapid simultaneous separations of both weakly retained anions and strongly retained polarisable anions was possible, with up to 10-fold decreases in overall run times. Coating stability and retention times under isocratic and isofluentic eluent conditions were shown to be reproducible over >450 repeat injections, with peak efficiency values averaging 29,000 N/m for the 2.5 cm column and 42,000 N/m for the 10 cm monolithic column, again under isocratic elution conditions.
Co-reporter:Eoin Gillespie, Miroslav Macka, Damien Connolly and Brett Paull
Analyst 2006 vol. 131(Issue 8) pp:886-888
Publication Date(Web):20 Jun 2006
DOI:10.1039/B606942H
The use of radial (across) capillary column capacitively coupled contactless conductivity detection is demonstrated as a simple and rapid technique for visualisation of stationary phase longitudinal coverage and coating stability in capillary ion exchange chromatography.
Co-reporter:Ekaterina P. Nesterenko;Leon P. Barron;Pavel N. Nesterenko
Journal of Separation Science 2006 Volume 29(Issue 2) pp:228-235
Publication Date(Web):8 FEB 2006
DOI:10.1002/jssc.200500335
Ion chromatography on a 4.0-mm-long (3.0 mm ID) ion exchange column is presented. Using a 10 mM phosphate buffer (pH 2.22) the separation of up to six UV-absorbing anions was obtained using the microcolumn, containing 5 μm RP support (Phenomenex Gemini) coated with the zwitterionic surfactant, (N-dodecyl-N,N-dimethylammonio) undecanoate. The short analytical column facilitated the application of a flow gradient programme over the flow range 0.3–5 mL/min resulting in optimum resolution of nitrite, nitrate, benzoate, iodide, thiocyanate and trichloroacetate in less than 10 min. The effect of both eluent concentration and pH on the retention of six selected anions was investigated, showing a strong pH capacity dependence. The microcolumn was found to exhibit no selectivity towards chloride and so was well suited to the analysis of saline samples. To illustrate this, the rapid analysis of a concentrated iodized table salt sample (20 g/L) was carried out. Following standard addition, a concentration of 3.55 ± 0.05 μg iodide/g and 1.05 ± 0.02 μg iodate/g in the solid salt sample was determined.
Co-reporter:Jonathan Bones, Kevin Thomas, Pavel N. Nesterenko, Brett Paull
Talanta 2006 Volume 70(Issue 5) pp:1117-1128
Publication Date(Web):15 December 2006
DOI:10.1016/j.talanta.2006.02.026
A simplified preconcentration method for a range of ultra-trace level pharmaceuticals in natural waters has been developed. Solid phase extraction was performed on-line using a micro-reversed-phase monolithic silica column, allowing for very rapid trace enrichment from large volume (500 ml) samples with minimal sample handling. Acceptable recoveries of >70% were obtained for the majority of compounds investigated and the monolithic columns could be washed and conditioned on-line with no sample carryover and used reproducibly for up to eight extractions each. The on-line SPE-LC-UV method was coupled to electrospray ionisation ion trap mass spectrometry (ESI-MS) to increase both selectivity and specificity. Detection limits were determined in spiked river and tap water samples and found to lie in the low ng/l region using sample volumes of 500 ml, loaded at a flow rate of 10 ml/min, and therefore, were suitable for ultra trace analysis.
Co-reporter:Leon Barron, Brett Paull
Talanta 2006 Volume 69(Issue 3) pp:621-630
Publication Date(Web):15 May 2006
DOI:10.1016/j.talanta.2005.10.032
A new analytical procedure for the simultaneous determination of trace oxyhalides and haloacetic acids (HAs) in drinking water and aqueous soil extracts is described. The method uses micro-bore ion chromatography (IC) coupled with suppressed conductivity (SC) and electrospray ionization mass spectrometric detection (ESI-MS). The IC–SC–ESI-MS system included a secondary flow of 100% MeOH, which was added to the column eluate (post-suppressor) and resulted in a significant increase in sensitivity for all analytes. All ESI-MS parameters were optimized for HA analysis and sensitivity quantitatively compared to suppressed conductivity. Full analytical performance characteristics for the developed method are presented for monochloro-, monobromo-, dichloro-, dibromo-, trichloro-, bromochloro, chlorodifluoro-, trifluoro-, dichlorobromo- and dibromochloroacetic acid, as well as the oxyhalides iodate, bromate, chlorate and perchlorate. In the case of the HAs, an optimised 25-fold SPE preconcentration method meant all analytes could be readily detected well below the USEPA 60 μg/L regulatory limit using conductivity and/or ESI-MS. The IC–ESI-MS method was applied to the determination of oxyhalides and HAs in both soil extracts and drinking water samples. Soil samples were extracted using ultra pure water with subsequent determination of perchlorate at 1.68 μg/g of soil. A drinking water sample containing HAs was preconcentrated using LiChrolut EN solid phase extraction cartridges with subsequent sulphate and chloride removal. Total HAs were determined at 13 μg/L.
Co-reporter:Brett Paull, Colmán Ó Ríordáin and Pavel N. Nesterenko
Chemical Communications 2005 (Issue 2) pp:215-217
Publication Date(Web):11 Nov 2004
DOI:10.1039/B414323J
An ultra-short 1.0 × 0.46 cm carboxybetaine coated monolithic anion exchanger has been used with a new double gradient ion chromatography (DG-IC) technique. The novel monolithic column can be used with flow rate gradients giving excellent peak efficiencies, and retention times can be simultaneously reduced through combining flow gradients with an eluent pH gradient.
Co-reporter:Edel Sugrue, Pavel N. Nesterenko, Brett Paull
Analytica Chimica Acta 2005 Volume 553(1–2) pp:27-35
Publication Date(Web):30 November 2005
DOI:10.1016/j.aca.2005.07.068
The high-performance separation of alkaline earth and transition metal ions on a bare porous silica 10.0 cm × 0.46 cm monolith (Merck Chromolith Si) was achieved using solvent enhanced ion chromatography. Using acetonitrile or methanol based ammonium and sodium acetate buffered mobile phases, the effect upon cation retention of mobile phase ionic strength, organic content and pH were evaluated. Increasing mobile phase acetonitrile concentration from 60 to 80% acetonitrile resulted in 10–15-fold increases in cation retention due to reduced hydration of the metal ions and hence enhanced ion-exchange interactions with surface silanol groups. The optimised conditions for the separation of Cu(II), Cd(II), Ni(II), Co(II) and Mn(II) were found to be 80% MeCN with 10.3 mM ammonium acetate (pH 4.6). Detection of transition metal ions was obtained using post-column reaction with 4-(2-pyridylazo) resorcinol and absorbance at 510 nm. Under elevated flow conditions (up to 5 mL/min), total runs times could be reduced to under 4 min. Optimum peak efficiencies were seen at flow rates of between 1.5 and 2 mL/min and were equivalent to an average efficiency of 25,000 N/m.
Co-reporter:Brett Paull and Pavel N. Nesterenko
Analyst 2005 vol. 130(Issue 2) pp:134-146
Publication Date(Web):21 Oct 2004
DOI:10.1039/B406355B
Ion chromatography (IC) has a proven track record in the determination of inorganic and organic anions and cations in complex matrices. Recently, application of IC to the separation and determination of bio-molecules such as amino acids, carbohydrates, nucleotides, proteins and peptides has also received much attention. The key to the determination of all of the above species in the most analytically challenging complex matrices is the ability to manipulate selectivity through control of stationary phase chemistry, mobile phase chemistry and the choice of detection method. This Tutorial Review summarises some of the most significant recent advances made in IC stationary phase technology. In particular, the review details stationary phases specifically designed for ion analysis in complex sample matrices, and considers in which direction future stationary phase development might proceed.
Co-reporter:Edel Sugrue, Pavel N. Nesterenko, Brett Paull
Journal of Chromatography A 2005 Volume 1075(1–2) pp:167-175
Publication Date(Web):20 May 2005
DOI:10.1016/j.chroma.2005.03.126
A 0.46 cm × 10.0 cm silica monolith column was modified through the in situ covalent attachment of lysine (2,6-diaminohexanoic acid) groups. Due to the zwitterionic nature of the resultant stationary phase, the modified monolithic column contained both cation and anion exchange capacity. In the case of cation exchange, the capacity was found to be relatively low at between 5 and 6.5 μmoles Me2+ per column. However, as expected, the lysine monolith exhibited a higher anion exchange capacity at 12–13 μmoles A− per column (at pH 3.0), which was found to be dependent upon column pH, due to the dissociation of the weak acid carboxylic acid groups. High-performance separations of transition metal cations and inorganic anions were achieved using the modified monolith, with the effects of eluent concentration, pH and flow rate evaluated. Using elevated flow rates of up to 5 mL/min the separation of nitrite, bromate, bromide, nitrate, iodide and thiocyanate was possible in approximately 100 s with peak efficiencies of between 50 and 100,000 N/m and retention time %RSD of under 0.3%.
Co-reporter:Leon Barron, Pavel N. Nesterenko, Brett Paull
Journal of Chromatography A 2005 Volume 1072(Issue 2) pp:207-215
Publication Date(Web):29 April 2005
DOI:10.1016/j.chroma.2005.03.028
Temperature programming was used to improve selectivity in the suppressed ion chromatographic (IC) separation of inorganic anions, haloacetic acids and oxyhalides in drinking water samples when using NaOH gradient elution. The programme exploited varying responses of these anions to changes in temperature. Heats of adsorption (ΔH, kJ/mol) for 17 anionic species were calculated from van’t Hoff plots. For haloacetic acids, both the degree of substitution and log P (log of n-octanol–water partition coefficient) values correlated well with the magnitude of the temperature effect, with monochloro- and monobromoacetic acids showing the largest effect (ΔH = −10.4 to −10.7 kJ/mol), dichloro- and dibromoacetic acids showing a reduced effect (ΔH = −6.8 to −8.4 kJ/mol) and trichloro-, bromodichloro- and chlorodibromoacetic acids showing the least effect (ΔH = −4.7 to −2.4 kJ/mol). The effect of temperature on oxyhalides ranged from ΔH = 8.4 kJ/mol for perchlorate to ΔH = −9.1 kJ/mol for iodate. The effectiveness of two commercial column ovens was investigated for the application of temperature gradients during chromatographic runs, with the best system applied to improve the resolution of closely retained species at the start, middle and end of the separation obtained using a previously optimised hydroxide gradient, in a real drinking water sample matrix. Retention time reproducibility of the final method ranged from 0.62 to 3.18% RSD (n = 30) showing temperature programming is indeed a practically important parameter to manipulate resolution.
Co-reporter:Éadaoin Tyrrell, Ceri Gibson, Brian D. MacCraith, David Gray, Pat Byrne, Nigel Kent, Conor Burke and Brett Paull
Lab on a Chip 2004 vol. 4(Issue 4) pp:384-390
Publication Date(Web):26 Apr 2004
DOI:10.1039/B400805G
The progressive development of a micro-fluidic manifold for the chemiluminescent detection of copper in water samples, based on the measurement of light emitted from the Cu(II) catalysed oxidation of 1,10-phenanthroline by hydrogen peroxide, is reported. Micro-fluidic manifolds were designed and manufactured from polymethylmethacrylate (PMMA) using three micro-fabrication techniques, namely hot embossing, laser ablation and direct micro-milling. The final laser ablated design incorporated a reagent mixing channel of dimensions 7.3 cm in length and 250 × 250 µm in width and depth (triangular cross section), and a detection channel of 2.1 cm in length and 250 × 250 µm in width and depth (total approx. volume of between 16 to 22 µL). Optimised reagents conditions were found to be 0.07 mM 1,10-phenanthroline, containing 0.10 mM cetyltrimethylammonium bromide and 0.075 M sodium hydroxide (reagent 1 delivered at 0.025 mL min−1) and 5% hydrogen peroxide (reagent 2 delivered at 0.025 mL min−1). The sample stream was mixed with reagent 1 in the mixing channel and subsequently mixed with reagent 2 at the start of the detection channel. The laser ablated manifold was found to give a linear response (R2 = 0.998) over the concentration ranges 0–150 µg L−1 and be reproducible (% RSD = 3.4 for five repeat injections of a 75 µg L−1 std). Detection limits for Cu(II) were found to be 20 µg L−1. Selectivity was investigated using a copper selective mini-chelating column, which showed common cations found in drinking waters did not cause interference with the detection of Cu(II). Finally the optimised system was successfully used for trace Cu(II) determinations in a standard reference freshwater sample (SRM 1640).
Co-reporter:Danielle Victory, Pavel Nesterenko and Brett Paull
Analyst 2004 vol. 129(Issue 8) pp:700-701
Publication Date(Web):15 Jun 2004
DOI:10.1039/B407483A
A 1.0 × 0.4 cm silica based monolithic anion exchanger has been produced and evaluated for use within a miniature gradient suppressed ion chromatography system based upon low-pressure micro-scale peristaltic pumps.
Co-reporter:Edel Sugrue;Pavel Nesterenko
Journal of Separation Science 2004 Volume 27(Issue 10‐11) pp:921-930
Publication Date(Web):7 JUL 2004
DOI:10.1002/jssc.200401794
A 10 cm silica monolith has been modified with iminodiacetic acid (IDA) groups and characterised for its selectivity toward alkali, alkaline earth, and selected transition metal cations. Physical characterisation of the modified monolith found non-homogeneous modification along the length of the monolith, although sufficient capacity was achieved to facilitate significant retention of alkaline earth and transition/heavy metal ions over a range of eluent pH and ionic strength conditions. For alkaline earth and transition/heavy metal ions, selectivity of the 10 cm IDA monolith closely matched that seen with a 25 cm IDA modified silica gel particle packed column, although the separation of alkali metal ions was noticeably poorer on the monolithic column. Peak efficiencies for most metal ions were of a similar order for both column types, except for Zn(II), which showed significant peak broadening on the IDA monolithic column.
Co-reporter:Damian Connolly;Danielle Victory
Journal of Separation Science 2004 Volume 27(Issue 10‐11) pp:912-920
Publication Date(Web):7 JUL 2004
DOI:10.1002/jssc.200401787
Short permanently coated reversed-phase silica based monolithic columns have been investigated for the rapid separation of inorganic anions and cations. One 2.5×0.46 cm column was permanently coated with didodecyldimethylammonium (DDAB), for anion analysis; and a second 5.0×0.46 cm column was coated with dioctylsulphosuccinnate (DOSS), for cation analysis. The use of a single combined eluent of 2.5 mM phthalate/1.5 mM ethylenediamine, at flow rates of between 4.0 and 8.0 mL/min, resulted in the rapid separation of 8 anions (in under 100 s) and 5 cations (in under 100 s) on the above columns when used individually, with detection limits for common anions ranging from approximately 0.25 to 5 mg/L, and between 2.5 and 50 mg/L for alkaline earth metals, by direct and indirect conductivity detection, respectively. However, with both columns subsequently connected in parallel, with the eluent delivered using a flow splitter from a single isocratic pump, the simultaneous analysis of anions and cations was also possible, based on a single conductivity detector. The potential of this system for the rapid, complete screening of water samples for multiple common anions and cations is shown.
Co-reporter:Edel Sugrue, Pavel Nesterenko and Brett Paull
Analyst 2003 vol. 128(Issue 5) pp:417-420
Publication Date(Web):17 Apr 2003
DOI:10.1039/B303467D
Iminodiacetic acid has been covalently bonded to a bare silica monolith to produce the first reported high-performance monolithic chelating ion exchange column. Using the new column, separation and determination of traces of alkaline earth metal ions (low ppm) in high ionic strength samples (up to 2 M NaCl and KCl brines), could be achieved in under 40 s. At an eluent flow rate of 4 mL min−1 retention time precision was <1.2%
(n
= 9) for Mg(II) and Ca(II), with detector linearity (n
= 5) over the range 2–10 mg L−1 of between R2
= 0.985 and R2
= 0.995. In 1 M KCl and NaCl brine samples, detection limits of 0.2 mg L−1 were possible.
Co-reporter:Brett Paull and Wasim Bashir
Analyst 2003 vol. 128(Issue 4) pp:335-344
Publication Date(Web):26 Mar 2003
DOI:10.1039/B300340J
The effect of column temperature upon the retention of metal ions on sulfonated and mono-, di-, and amino-carboxylated cation exchange columns has been investigated. The retention of alkali, alkaline earth and transition metal ions on each of the above types of cation exchanger was studied over the temperature range 19–65 °C. A major difference between the behaviour of mono- and divalent metal ions was shown on each of the above stationary phases, with the monovalent alkali metals exhibiting clearly exothermic behaviour (a decrease in retention with increased temperature) under acidic eluent conditions and an apparent relationship between retention factor and the magnitude of the temperature effect. The effect of temperature upon alkaline earth metal ions was less defined, although strongly endothermic behaviour (increase in retention with temperature) could be seen on all stationary phases through correct choice of eluent. The transition metal ions studied showed endothermic behaviour on all four stationary phases, with the sulfonated column unexpectedly showing the largest increases in retention. The above behaviour can be partially explained through the dominance of the type of solute-stationary phase interaction governing retention. In several of the above columns, both ion-exchange and surface complexation interactions can occur, with the effects of temperature indicating which process dominates under specific eluent conditions.
Co-reporter:Ekaterina Nesterenko, Oksana Yavorska, Mirek Macka, Alexander Yavorskyy and Brett Paull
Analytical Methods (2009-Present) 2011 - vol. 3(Issue 3) pp:
Publication Date(Web):
DOI:10.1039/C0AY00649A
Co-reporter:Hassan Alwael, Damian Connolly and Brett Paull
Analytical Methods (2009-Present) 2011 - vol. 3(Issue 1) pp:NaN69-69
Publication Date(Web):2010/11/25
DOI:10.1039/C0AY00516A
A solid phase extraction, liquid chromatography and fluorescence (SPE-RPLC-FL) based protocol for the determination of free monosaccharides in highly complex raw material powders and formulated fermentation feedstocks and broths has been developed. Monosaccharides within sample extracts were derivatised pre-column with anthranilic acid and the derivatives separated using reversed-phase LC with fluorescence detection. Using a 2.1 mm × 50 mm 1.8 µm Zorbax Eclipse XDB-C18 column, a flow rate of 0.4 mL min−1 and an acetonitrile gradient in a sodium acetate buffer (pH 4.3; 50 mmol L−1) the baseline resolution of glucosamine, mannosamine, galactosamine, galactose, mannose, glucose, ribose, xylose, fucose and sialic acid within 20 minutes was achieved. Pre-column derivatisation involved combining a 30 mg mL−1 solution of anthranilic acid in a 1:1 ratio with an aqueous standard prior to injection. Standard analytical performance criteria were used for evaluation purposes, with the method found to exhibit LOD's as low as 10 fmol, and be linear and precise (%RSD < 2.2% (n = 7). The method was applied to the analysis of a range of highly complex biopharmaceutical production samples, including yeastolate powders, chemically defined media and in-process fermentation broth samples. Sample preparation involved passing an aqueous sample through a C18 solid phase extraction cartridge to trap hydrophobic peptides and vitamins, with recovery of all test sugars exceeding 90%. Finally, standard statistical analysis was performed on samples taken from different lots in order to estimate lot-to-lot variability.
Co-reporter:Jonathan Bones, Kevin V. Thomas and Brett Paull
Environmental Science: Nano 2007 - vol. 9(Issue 7) pp:NaN707-707
Publication Date(Web):2007/05/17
DOI:10.1039/B702799K
A solid phase extraction (SPE) method has been developed and applied in conjunction with a previously reported liquid chromatography tandem mass spectrometry (LC–MS–MS) procedure for the determination of illicit drugs and abused pharmaceuticals in treated wastewater and surface water samples at the ng L−1 level. A full method validation was also performed and determined levels of analytical sensitivity were found to lie in the 1–10 ng L−1 range using river water as a test sample matrix and a sample size of 500 mL. The developed procedure was successfully applied for the determination of the chosen analytes in wastewater treatment plants in Dublin, Ireland and rapidly expanding commuter towns in the surrounding counties. Cocaine was detected in 70% of the collected samples in the range of 25–489 ng L−1, its primary metabolite, benzoylecognine (BZE) was also detected in the range of 22–290 ng L−1. Other substances detected included morphine, Tempazepam and the primary metabolite of methadone.
Co-reporter:Wasim Bashir, Frank McGovern, Phillip O'Brien, Margaret Ryan, Liam Burke and Brett Paull
Environmental Science: Nano 2008 - vol. 10(Issue 6) pp:NaN738-738
Publication Date(Web):2008/05/16
DOI:10.1039/B803010C
A major Irish study, based upon more than 8000 samples collected over the measurement period of 22 years, for sulfur dioxide (SO2–S), sulfate (SO4–S) and nitrogen dioxide (NO2–N) concentrations (μg m−3) within air, and the ionic composition of precipitation samples based on sodium (Na+), potassium (K+), magnesium (Mg2+), calcium (Ca2+), chloride (Cl−), sulfate (SO4–S), non-sea salt sulfate (nssSO4–S), ammonium (NH4–N), and nitrate (NO3–N) weighted mean concentrations (mg l−1), has been completed. For the air samples, the sulfur dioxide and sulfate concentrations decreased over the sampling period (1980–2004) by 75% and 45%, respectively, whereas no significant trend was observed for nitrogen dioxide. The highest concentrations for sulfur dioxide, sulfate and nitrogen dioxide were associated with wind originating from the easterly and northeasterly directions i.e. those influenced by Irish and European sources. The lowest concentrations were associated with the westerly directions i.e. for air masses originating in the North Atlantic region. This was further verified with the use of backward (back) trajectory analysis, which allowed tracing the movement of air parcels using the European Centre for Medium range Weather Forecasting (ECMWF) ERA-40 re-analysis data. High non-sea salt sulfate levels were being associated with air masses originating from Europe (easterlies) with lower levels from the Atlantic (westerlies). With the precipitation data, analysis of the non-sea salt sulfate concentrations showed a decrease by 47% since the measurements commenced.
Co-reporter:Leon Barron, John Tobin and Brett Paull
Environmental Science: Nano 2008 - vol. 10(Issue 3) pp:NaN361-361
Publication Date(Web):2008/02/18
DOI:10.1039/B717453E
An analytical method to determine a selection of 27 frequently prescribed and consumed pharmaceuticals in biosolid enriched soils and digested sludges is presented. Using a combination of pressurized liquid extraction, solid phase extraction and liquid chromatography with tandem mass spectrometry, it was possible to detect all analytes in each sample type at the low-sub ng g−1 level. Solid phase extraction efficiencies were compared for 6 different sorbent types and it was found that Waters Oasis HLB cartridges offered enhanced selectivities with 20 analytes showing final method recoveries ≥60% in both soils and digested sludges. The method was validated for linearity, range, precision and limits of detection in both sample matrices. All analytes were then determined in sludge enriched soils as well as the precursor thermally dried sludge fertilizer produced from a primary wastewater treatment plant. Levels of the antibacterial agent triclosan were found to exceed 20 μg g−1 in digested sludge and 5 μg g−1 in thermally dried sludge cake. Significant traces of carbamazepine and warfarin were also detected in the above samples.
![Methyl (3s,4r)-3-benzoyloxy-8-methyl-8-azabicyclo[3.2.1]octane-4-carboxylate](http://img.cochemist.com/ccimg/100/50-36-2.png)
![Methyl (3s,4r)-3-benzoyloxy-8-methyl-8-azabicyclo[3.2.1]octane-4-carboxylate](http://img.cochemist.com/ccimg/100/50-36-2_b.png)
![8-Azabicyclo[3.2.1]octane-2-carboxylicacid, 3-(benzoyloxy)-8-methyl-, ethyl ester, (1R,2R,3S,5S)-](http://img.cochemist.com/ccimg/600/529-38-4.png)
![8-Azabicyclo[3.2.1]octane-2-carboxylicacid, 3-(benzoyloxy)-8-methyl-, ethyl ester, (1R,2R,3S,5S)-](http://img.cochemist.com/ccimg/600/529-38-4_b.png)
![8-Azabicyclo[3.2.1]octane-2-carboxylicacid, 3-(benzoyloxy)-8-methyl-, (1R,2R,3S,5S)-](http://img.cochemist.com/ccimg/600/519-09-5.png)
![8-Azabicyclo[3.2.1]octane-2-carboxylicacid, 3-(benzoyloxy)-8-methyl-, (1R,2R,3S,5S)-](http://img.cochemist.com/ccimg/600/519-09-5_b.png)
![2-Propanol, 1-[(1-methylethyl)amino]-3-(1-naphthalenyloxy)-](/data/chemimg/935900/525-66-6.png)
![2-Propanol, 1-[(1-methylethyl)amino]-3-(1-naphthalenyloxy)-](/data/chemimg/935900/525-66-6_b.png)
![Spiro[2H-1-benzopyran-2,2'-[2H]indole]-1'(3'H)-propanoic acid, 3',3'-dimethyl-6-nitro-](/data/chemimg/583600/55779-26-5.png)
![Spiro[2H-1-benzopyran-2,2'-[2H]indole]-1'(3'H)-propanoic acid, 3',3'-dimethyl-6-nitro-](/data/chemimg/583600/55779-26-5_b.png)
![[4-(4-AMINO-6,7-DIMETHOXY-QUINAZOLIN-2- YL)PIPERAZIN-1-YL]-(2,5-DIOXABI CYCLO[4.4.0]DECA-6,8,10-TRIEN-4-YL)METHANONE](http://img.cochemist.com/ccimg/74200/74191-85-8.png)
![[4-(4-AMINO-6,7-DIMETHOXY-QUINAZOLIN-2- YL)PIPERAZIN-1-YL]-(2,5-DIOXABI CYCLO[4.4.0]DECA-6,8,10-TRIEN-4-YL)METHANONE](http://img.cochemist.com/ccimg/74200/74191-85-8_b.png)
![3',6'-Dihydroxy-3H-spiro[isobenzofuran-1,9'-xanthen]-3-one](http://img.cochemist.com/ccimg/2400/2321-07-5.png)
![3',6'-Dihydroxy-3H-spiro[isobenzofuran-1,9'-xanthen]-3-one](http://img.cochemist.com/ccimg/2400/2321-07-5_b.png)