Particle concentration and filtration is a key stage in a wide range of processing industries and also one that can be present challenges for high throughput, continuous operation. Here we demonstrate some features which increase the efficiency of ultrasound enhanced sedimentation and could enable the technology the potential to be scaled up. In this work, 20 mm piezoelectric plates were used to drive 100 mm high chambers formed from single structural elements. The coherent structural resonances were able to drive particles (yeast cells) in the water to nodes throughout the chamber. Ultrasound enhanced sedimentation was used to demonstrate the efficiency of the system (>99% particle clearance). Sub-wavelength pin protrusions were used for the contacts between the resonant chamber and other elements. The pins provided support and transferred power, replacing glue which is inefficient for power transfer. Filtration energies of ∼4 J/ml of suspension were measured. A calculation of thermal convection indicates that the circulation could disrupt cell alignment in ducts >35 mm high when a 1K temperature gradient is present; we predict higher efficiencies when this maximum height is observed. For the acoustic design, although modelling was minimal before construction, the very simple construction allowed us to form 3D models of the nodal patterns in the fluid and the duct structure. The models were compared with visual observations of particle movement, Chladni figures and scanning laser vibrometer mapping. This demonstrates that nodal planes in the fluid can be controlled by the position of clamping points and that the contacts could be positioned to increase the efficiency and reliability of particle manipulations in standing waves.

A new design of miniaturised free flow electrophoresis device has been produced. The design contains a separation chamber that is 45 mm long by 31.7 mm wide with a depth of 50 μm 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.

This work shows how the inclusion of cryptand 222 as a leading electrolyte additive in isotachophoresis affects the electrophoretic mobilities of alkali metal cations. Using isotachophoresis the separation of alkali metals can be difficult due to the similar electrophoretic mobilities of three of the ions: caesium, rubidium and potassium. However, the presence of cryptand 222 in the leading electrolyte retards the mobilities of the caesium, rubidium and potassium to a different extent allowing separations to be made. A novel electrolyte system was formulated which consisted of a leading electrolyte of 10 mM caesium hydroxide, 0.75 mM cryptand 222 buffered to pH 9.4 with glycylglycine and a terminating electrolyte of 10 mM tetrabutylammonium hydroxide. The use of this electrolyte system allowed good separations of mixtures of rubidium, potassium, sodium and lithium to be achieved. The method was also applied to the analysis of edible salt samples.

A new method has been developed to improve the determination of thiocyanate using isotachophoresis. This method uses complexation with copper(II) as a mechanism for improving the separation of thiocyanate from chlorate and perchlorate. By using a pH of 3.25 the method can also be used to analyse nitrite. Separations were carried out using a miniaturised poly(methyl methacrylate) (PMMA) separation device. Linearity was observed from 1.25 to 75 mg dm(-3) with a correlation coefficient of 0.998 for both thiocyanate and nitrite. Limits of detection for these two species were calculated to be 0.8 mg dm(-3) and 0.9 mg dm(-3) respectively. The method was successfully applied to the analysis of these anions in a range of samples including explosive residues.

A new method has been developed to allow the determination of potassium in post-explosion residues to be made using miniaturised isotachophoresis. The method is based on the use of a caesium leading ion with 4.5 mM 18-crown-6 ether added to retard the potassium to allow reliable determinations to be made. With the conditions selected no interference was noted from other small inorganic cations, such as ammonium, barium, calcium, magnesium, sodium or strontium. The method was successfully applied to the analysis of seven samples containing explosive residues obtained from the unconfined burning of several flash powders. The procedure was found to offer good linearity for potassium determinations over the concentration range of 1.25-150 mu g/mL with a coefficient of determination of 0.999 achieved.

The foremost requirement of quantification of cellulases expressed in genetically modified sugarcane is an efficient sample clean-up. This work investigates the feasibility of isotachophoresis for this purpose. An electrolyte system comprising a leading electrolyte of 10 mM formic acid at pH 9.0 and a terminating electrolyte of 10 mM β-alanine was devised and used to perform isotachophoresis of cellulases. The use of a simple front cutting method removed a majority of interfering species in the juice, thereby resulting in the formation of a distinct zone of desired proteins. In comparison to techniques such as ultrafiltration and liming, the analysis time and loss of desired proteins was lower when the sample was prepared by using isotachophoresis. Hence, isotachophoresis was an ideal choice for purification of the proteins in question from the remaining components in the juice.

The use of malonic acid as a complexing agent has enabled a new method to be devised to allow the determination of magnesium to be made using miniaturised isotachophoresis. Using a leading electrolyte of 10 mmol L(-1) caesium hydroxide and 2 mmol L(-1) malonic acid at pH 5.1 gave the method a high specificity towards magnesium. Investigations using a poly(methyl methacrylate) chip device with an integrated conductivity detector showed that no interference from calcium, strontium, barium and sodium should occur. The method was found to be linear over the range of magnesium concentrations from 0.625 to 75 mg L(-1) and the limit of detection was calculated to be 0.45 mg L(-1). Separations were demonstrated with water samples but the procedure should also be applicable to more complex sample matrices such as inorganic explosive residues, blood or urine.

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.

A new type of miniaturized separation chip for performing isotachophoresis has been produced. The design uses polystyrene as a substrate material and incorporates carbon fibre loaded polystyrene drive and conductivity detection electrodes. This fully polymeric composition allows for the devices to be produced using injection moulding. Ultrasonic welding is used for sealing to give robust chips that can potentially be easily transported and used outside of a laboratory environment. A batch of devices was produced and tested with a number of inorganic cationic species as samples. The entire batch of 22 devices were successfully used for isotachophoretic separations. Good reproducibility was observed in the qualitative behaviour of the devices. For example, with lithium a relative step height ± standard deviation of 1.49 ± 0.01 was observed on a run-to-run basis with a single chip and of 1.47 ± 0.03 on a chip-to-chip basis over the entire batch of devices.

A variable-volume sample injector design is presented and evaluated for performing sample introduction protocols for carrying out miniaturised isotachophoresis (ITP) separations. The microdevice design features a wide bore sample loop channel connected to a narrower bore separation channel via a short injection channel angled at 45°. An additional side arm channel located at the injection point enabled a range of injection strategies, using a gravity-fed system, to be implemented and assessed. A model analyte was used to demonstrate the versatility of the injector design for low and high sample loading regimes suitable for concentrated and dilute sample solutions, respectively.

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.

A new method has been devised to allow the determination of small inorganic anions using isotachophoresis. This method makes use of indium(III) as a counter ion to manipulate the effective mobilities of inorganic anion species by means of complexation reactions. This new procedure successfully allowed the simultaneous determination of nitrate, chloride and sulphate to be realised on a capillary scale instrument and in a chip-based separation device. The electrolyte system developed to allow the separation to be achieved employed a 10mM bromide-based leading electrolyte containing 1.25mM indium(III) at pH 3.15 and a terminating electrolyte of cyanoacetic acid.