Biomedical subjects

Brett Paull

Publications and source records attributed to Brett Paull.

28 records · Page 2Linked to original sources

PubMed2004

Rapid screening of selected organic explosives by high performance liquid chromatography using reversed-phase monolithic columns.

This study presents the rapid screening of various high grade explosives by high performance liquid chromatography (HPLC) with monolithic stationary phases. Two gradient methods were developed, the first for quantitative analysis of eleven explosives: HMX; RDX; Tetryl; TNT; 2,3-DNT; 2,6-DNT; 3,4-DNT; 2-NT; 3-NT; 4-NT; and PETN in under 14 min. The second method separated seven explosives in under two min and is suitable for rapid screening to determine the presence of specific and/or class of explosive. The rapid screening methods were successfully applied to soils spiked with known amounts of target explosives. This technology showed excellent potential for forensic explosives detection and analysis.

Journal Article↗

PubMed2003

Quantitative capillary zone electrophoresis of inorganic anions.

Despite the availability of commercial capillary electrophoresis systems for over ten years, where quantitative analysis is required, capillary zone electrophoresis (CZE) has often failed to replace ion chromatography as the method of choice for a large number of analytes, not least inorganic anions. To investigate the reasons for this apparent failing, a review is presented of work that has been carried out to-date involving the quantitative application of CZE to the determination of inorganic anions in industrial and environmental samples. This review summarizes work both investigating and improving the quantitative aspects of the CZE of inorganic anions. A complete survey of how CZE has been applied to the determination of inorganic anions in real samples is given, including what, if any, analytical performance parameters were investigated and quoted, and if quality assurance data and validation methods were briefly considered, thoroughly investigated or simply ignored.

Anions↗

PubMed2003

Non-trivial temperature effects on the cation exchange chromatography and chelation ion chromatography of metal ions.

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 degrees 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.

Journal Article↗

PubMed2003

Iminodiacetic acid functionalised monolithic silica chelating ion exchanger for rapid determination of alkaline earth metal ions in high ionic strength samples.

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.

Journal Article↗

PubMed2002

Zwitterionic ion chromatography using a dynamically coated column and mobile phase recycling.

An investigation into the use of zwitterionic ion chromatography for the determination of inorganic anions in water samples was carried out. When using an ODS stationary phase precoated with Zwittergent 3-14 and a pure water mobile phase, the stability of the adsorbed coating was insufficient for quantitative work. Recycling of the water mobile phase was used to stabilise the zwitterionic coating, and resulted in improved retention time precision (15.2% RSD down to 2.4% RSD for nitrate). Post-detection cation- and anion-exchange columns in acid and hydroxide form removed sample ions from the recycling mobile phase, with the desorbed Zwittergent 3-14 passing through unretained and passing back through the pump to the analytical column. A 200-ml volume of mobile phase was recycled over a 3-week period with retention times for sulphate, chloride and nitrate standards injected at the start and end of the period varying less than 2.5%. The same system was then used with a mobile phase containing 2 mM Zwittergent 3-14. This resulted in further improvements in retention time (0.2-0.5% RSD, n = 10) and peak area precision (2.6-6.0% RSD, 1 mM standards) and improved peak efficiencies (2421-4047 N). The developed method was applied to water samples, and results compared to those obtained using anion-exchange chromatography. All sample cations were exchanged to sodium using an off-line cation-exchange procedure prior to injection.

Chromatography, Ion Exchange↗

PubMed2002

Retention of alkali, alkaline earth and transition metals on an itaconic acid cation-exchange column. Eluent pH, ionic strength and temperature effects upon selectivity.

The unusual selectivity of a methylene succinic (itaconic) acid modified polymeric column was investigated for the separation of alkali, alkaline earth, transition and heavy metals employing non-chelating inorganic eluents. The retention of selected metal ions on the column was investigated with simple HNO3 eluents and eluents prepared from KNO3 and KCl salts of varying pH (adjusted using HNO3). From these studies both the effect of eluent ionic strength and pH upon retention was evaluated for the itaconic acid stationary phase. The results obtained showed that despite slow exchange kinetics causing poor efficiencies, acceptable baseline separations of selected alkaline earth and transitions could be obtained under optimum conditions (the baseline separation of Mg(II), Ca(II), Mn(II), Cd(II), Zn(II) and Co(II) was possible using a 15 mM KNO3-5 mM KCl eluent at pH 3.50 in under 25 min). The use of an simple ionic strength step gradient was shown that facilitated the addition of Pb(II) to the above group of metal ions. An investigation into the effect of temperature upon peak efficiency and retention showed increased column temperature could be used to improve the resolution of closely eluting metal ions such as Ca(II) and Sr(II) and Ca(II) and Mn(II).

Alkalies↗

PubMed2002

Fast ion chromatography of common inorganic anions on a short ODS column permanently coated with didodecyldimethylammonium bromide.

Fast ion-exchange chromatography has been developed and applied to the separation of common inorganic anions. Using a didodecyldimethylammonium bromide (DDAB) coated short (30 mm x 4.6 mm) ODS analytical column (3-microm particle size) and a 5 mM phthalate eluent (pH 7.5) the isocratic separation of nine common anions in 160 s was possible, with the first seven anions, including phosphate, chloride and sulphate, separated within 65 s. Detection was achieved using indirect UV at 279 nm. The high capacity, highly hydrophobic ion-exchange coating demonstrated excellent stability over time, even at elevated temperatures (45 degrees C) and exhibited unusual selectivity for common anions (retention order=fluoride, carbonate, phosphate, chloride, bromate, nitrite, sulphate, bromide and nitrate). The developed chromatography was successfully applied to the rapid analysis of river water and seawater samples.

Anions↗

PubMed2002

Determination of urinary thiocyanate and nitrate using fast ion-interaction chromatography.

A simple and rapid chromatographic method for determination of nitrite, nitrate and thiocyanate is reported, and applied to the analysis of non-, medium and heavy smokers' urine samples. Ion-interaction liquid chromatography was carried out on a short 30 mm x 4.6 mm C18 column (3 microm particle size) with a mobile phase of 10 mM tetrabutylammonium phosphate in 20% MeOH. The chromatography was performed at an elevated temperature of 45 degrees C, at a flow-rate of 1 ml/min. Detection was by direct UV absorption at 230 nm. Sample preparation involved centrifugation and dilution, followed by sample clean-up on a C18 solid-phase extraction cartridge. The developed method proved both precise (% RSD <2%) and sensitive (standard detection limits <0.1 mg/l), and yielded total run times of under 10 min when applied to urine analysis of smokers and non-smokers, with thiocyanate eluting in under 5 min.

Chromatography, Liquid↗

PubMed2002

Ionic strength, pH and temperature effects upon selectivity for transition and heavy metal ions when using chelation ion chromatography with an iminodiacetic acid bonded silica gel column and simple inorganic eluents.

An investigation into the selectivity of an iminodiacetic acid (IDA) modified silica gel column for transition and heavy metal ions using non-chelating inorganic eluents has been carried out. A number of eluent parameters were investigated to determine the exact retention mechanism taking place and to control selectivity. The parameters studied were eluent ionic strength and the nature of the inorganic salt used, eluent pH and eluent temperature. The results obtained showed how despite certain metal ions exhibiting similar stability constants with the bonded IDA groups, careful control of each of the above parameters, in particular eluent chloride ion concentration and eluent temperature, could result in large changes in selectivity. Optimal conditions for the isocratic and gradient separation of Mg(II), Ca(II), Mn(II), Cd(II), Co(II), Zn(II) and Pb(II) were determined. An isocratic method using a 0.035 M KCl, 0.065 M KNO3 (pH 2.5) eluent was successfully applied to the determination of Mn(II), Cd(II), Co(II) and Zn(II) at concentrations between 20 and 121 microg/l in a freshwater certified reference material (NIST 1640).

Chelating Agents↗

PubMed2002

Performance of a simple UV LED light source in the capillary electrophoresis of inorganic anions with indirect detection using a chromate background electrolyte.

Light emitting diodes (LEDs) are known to be excellent light sources for detectors in liquid chromatography and capillary electromigration separation techniques, but to date only LEDs emitting in the visible range have been used. In this work, a UV LED was investigated as a simple alternative light source to standard mercury or deuterium lamps for use in indirect photometric detection of inorganic anions using capillary electrophoresis with a chromate background electrolyte (BGE). The UV LED used had an emission maximum at 379.5 nm, a wavelength at which chromate absorbs strongly and exhibits a 47% higher molar absorptivity than at 254 nm when using a standard mercury light source. The noise, sensitivity and linearity of the LED detector were evaluated and all exhibited superior performance to the mercury light source (up to 70% decrease in noise, up to 26.2% increase in sensitivity, and over 100% increase in linear range). Using the LED detector with a simple chromate-diethanolamine background electrolyte, limits of detection for the common inorganic anions, Cl-, NO3-, SO4(2-), F- and PO4(3-) ranged from 3 to 14 microg L(-1), using electrostatic injection at -5 kV for 5 s.

Journal Article↗