Search

A new method allowing the simultaneous determination of arsenic(V), selenium(IV) and selenium(VI) using miniaturised isotachophoresis has been developed. The method uses 0.02 M nitric acid buffered to pH 5.5 with histidine as the leading electrolyte. Using a miniaturised poly(methyl methacrylate) chip device with an integrated conductivity detector, separations of model samples and an industrial process stream sample were achieved. Limits of detection were calculated to be 0.85 mg L−1 for arsenic(V), 0.95 mg L−1 for selenium(IV) and 1.0 mg L−1 for selenium(VI). A method for the analysis of arsenic(III), using a glycolic acid based leading electrolyte to eliminate carbonate interference is also presented. [ABSTRACT FROM AUTHOR]

The use of miniaturised isotachophoresis to allow the simultaneous determination of two inorganic selenium species has been investigated using a poly(methyl methacrylate) chip with a 44-mm-long, 200-μm-wide, 300-μm-deep separation channel. The miniaturised device included an integrated on-column, dual-electrode conductivity detector and was used in conjunction with a hydrodynamic fluid transport system. A simple electrolyte system has been developed which allowed the separation of selenium(IV) and selenium(VI) species to be made in under 210 s. The limits of detection were calculated to be 0.52 mg L-1 for selenium(IV) and 0.65 mg L-1 for selenium(VI). The method allowed the separation of the selenium species from a range of common anions including fluoride, nitrate, nitrite, phosphate, sulfate and sulfite. [ABSTRACT FROM AUTHOR]

Abstract: A new design of miniaturised free flow electrophoresis device has been produced. The design contains a separation chamber that is 45mm long by 31.7mm wide with a depth of 50μm and has nine inlet and nine outlet holes to allow for fraction collection. The devices were formed of polystyrene with carbon fibre loaded polystyrene drive electrodes and produced using injection moulding. This means that the devices are low cost and can potentially be mass produced. The devices were used for free flow isotachophoresis (FFITP), a technique that can be used for focussing and concentrating analytes contained within complex sample matrices. The operation of the devices was demonstrated by performing separations of dyes and bacterial samples. Analysis of the output from FFITP separations of samples containing the bacterium Erwinia herbicola, a biological pathogen, by cell culturing and counting showed that fractionation of the output was achieved. [Copyright &y& Elsevier]

Abstract: A new design of miniaturised separation device for performing isotachophoresis (ITP) has been produced. The device contains a simple arrangement of channels comprising a single separation channel with a ‘double T’ injection geometry. The device was produced in poly(methyl methacrylate) and incorporates an on-column conductivity detector. A new electrolyte system was developed to enable the rapid determination of chloride to be made. This electrolyte system uses a leading ion of 3.5mM nitrate at pH 3.0 with 0.5mM indium(III) added as a complexing agent. Use of this electrolyte system with the new separation device allowed chloride samples to be analysed in under 100s, with a limit of detection (LOD) calculated to be 2.2mgl−1. [Copyright &y& Elsevier]

A method allowing the miniaturised isotachophoretic analysis of amino acids has been developed. To overcome the problems of carbonate contamination which occur when performing separations at alkaline pH levels glycolate was used as the leading ion. Addition of magnesium to the leading electrolyte as a counter species was found to improve the separations. The method has been used on a poly(methyl methacrylate) microdevice with integrated on-column conductivity detectors. The behaviour of a range of common amino acids was investigated and successful separations of up to seven amino acids were made. Good linearity was observed with calibration curves for aspartic acid and phenylalanine over the range 0.063–1.0 mM. Limits of detection for these two species were calculated to be 0.060 and 0.018 mM, respectively. [Copyright &y& Elsevier]

An electrolyte system, using malic acid as a complexing agent, has been developed to allow the determination of transition metal cations using miniaturised isotachophoresis. The method allowed the simultaneous determination of Mn2+, Cr3+, Fe2+, Co2+, Zn2+ and Ni2+ to be made without interference from other common ions. Limits of detection were calculated to be in the range 0.5–1.0mgl-1 for Mn2+, Cr3+ Co2+and Zn2+ and 2.0mgl-1 for Fe2+ and 4.7mgl-1 for Ni2+. The successful analysis of five industrial samples, containing a range of these metal ions, obtained from metal processing plants were achieved in under 13min. The separations were performed on a poly(methyl methacrylate) chip with integrated platinum wire conductivity detection electrodes. [Copyright &y& Elsevier]

Abstract: A new method has been developed to allow the determination of the chlorate, chloride and perchlorate anions in inorganic explosive residues to be made using isotachophoresis (ITP). To enable a good separation of these species to be achieved the method involves the use of two complexing agents. Indium(III) is used to allow the determination of chloride whilst using nitrate as the leading ion and α-cyclodextrin is used to allow the separation of chlorate and perchlorate. Separations were carried out using a miniaturised poly(methyl methacrylate) (PMMA) separation device. The method was applied to analysing both model samples and actual inorganic explosive containing residue samples. Successful determinations of these samples were achieved with no interference from other anions typically found in inorganic explosive residues. Limits of detection (LOD) for the species of interest were calculated to be 0.80mgl−1 for chloride, 1.75mgl−1 for chlorate and 1.40mgl−1 for perchlorate. [Copyright &y& Elsevier]

Abstract: This paper presents the findings of a feasibility study investigating the behaviour of DNA under conditions of miniaturised isotachophoresis. An electrolyte system comprising a leading electrolyte of 5mM perchloric acid at pH 6.0 and a terminating electrolyte of 10mM gallic acid was devised and used to perform isotachophoresis of DNA containing samples on a miniaturised poly(methyl methacrylate) device. Under such conditions it was found that no separation of DNA fragments was observed with the substance migrating instead as a single isotachophoretic zone. Whilst such a result shows the method is unsuitable for analysis DNA it offers significant potential as a means of sample preparation for subsequent analysis using another method. This is because the single zone of DNA formed is preconcentrated to a constant concentration governed by the leading ion and is separated from all species with different effective electrophoretic mobilities. [Copyright &y& Elsevier]

Abstract: An injection moulded free flow isotachophoresis (FFITP) microdevice with integrated carbon fibre loaded electrodes with a separation chamber of 36.4mm wide, 28.7mm long and 100μm deep is presented. The microdevice was completely fabricated by injection moulding in carbon fibre loaded polystyrene for the electrodes and crystal polystyrene for the remainder of the chip and was bonded together using ultrasonic welding. Two injection moulded electrode designs were compared, one with the electrode surface level with the separation chamber and one with a recessed electrode. Separations of two anionic dyes, 0.2mM each of amaranth and acid green and separations of 0.2mM each of amaranth, bromophenol blue and glutamate were performed on the microdevice. Flow rates of 1.25mlmin−1 for the leading and terminating electrolytes were used and a flow rate of 0.63mlmin−1 for the sample. Electric fields of up to 370Vcm−1 were applied across the separation chamber. Joule heating was not found to be significant although out-gassing was observed at drive currents greater than 3mA. [Copyright &y& Elsevier]