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Mercury is a toxic environmental contaminant that can cause serious health problems. This work describes a new type of eco-friendly three-electrode plastic sensor chip for the determination of trace Hg(II) by means of anodic stripping voltammetry (ASV). The sensor chip is entirely fabricated by injection moulding, which is a sustainable manufacturing method, and consists of three conductive carbon-based electrodes embedded in a plastic holder while the reference electrode is coated with Ag using e-beam evaporation. The sample is spiked with Au(III) which deposits on the working electrode in the form of gold nanoparicles during the analysis; the target Hg(II) co-deposits on the gold nanoparticles forming a Au(Hg) amalgam in situ. The accumulated Hg is stripped off the electrode and quantified by an anodic square wave potential scan. The relevant conditions and the potential interferences are investigated. The limit of detection for Hg(II) is 0.4 μg L−1 and the repeatability at the 20 μg L−1 Hg(III) level (n = 10) is 5.3%. The sensor is applied to water, honey, fish oil and mussel samples with recoveries between 98 and 107%. [Display omitted] • A plastic integrated electrochemical sensor is fabricated by injection moulding. • The sensor is applied to the determination of Hg(II) by means of stripping voltammetry with a LOD of 0.4 μg L−1 • Au(III) co-deposits with Hg(II) on the working electrode forming a Au(Hg) amalgam. • The instrumental/chemical conditions and the interferences are studied. • The sensor is applied to the analysis of food and water samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • A rapid voltammetric method for monitoring of trace Αs(III) was developed. • Disposable injection-moulded sensors are used in a portable configuration. • Detection is performed at an in-situ electroplated gold film electrode. • A sub-μg L-1 limit of detection is achieved for As(III) • The interference by Cu(II) is alleviated using potassium ferrocyanide. This work reports the fabrication of portable system for the determination of trace As(III) in water samples by mean of anodic stripping voltammetry (ASV). The portable detection system consists of a three-electrode mini cell featuring injection-moulded plastic conductive electrodes. As(III) accumulates on the disposable working electrode by electrolysis forming in situ an alloy with co-deposited gold. Then, the accumulated arsenic is detected by applying an anodic potential scan on the working electrode. The chemical and instrumental conditions were studied and the analytical parameters for the determination of As(III) were established. The limit of detection was 0.2 μg L-1 and the repeatability at the 5.0 μg L-1 As(III) level (n = 10) was 4.7 %. The portable set-up was applied to different groundwater samples with recoveries between 95 and 105 %. [ABSTRACT FROM AUTHOR]

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 1 K 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. [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: Cellobiohydrolase (CBH) is an important enzyme for the conversion of lignocellulosic biomass to ethanol. This work separated the glycoforms of CBH possessing different numbers of neutral mannoses using capillary zone electrophoresis (CZE) in a 50mM, pH 7.5 phosphate buffer. The method analysed CBH in an intact form using a polyacrylamide coated fused silica capillary without requiring additives or labelling of the enzyme. The migration time of the major peak was found to be 21.6±0.1min (n =3) and the approach is suitable for testing of batch-to-batch consistency of CBH. Ease-of-use, automation and speed are the other benefits due to which the use of CZE for analysing glycoforms of CBH was concluded to be ideal. [Copyright &y& Elsevier]

Abstract: 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 10mM formic acid at pH 9.0 and a terminating electrolyte of 10mM 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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]

This work describes a sequential injection analysis (SIA) method for on‐line strippping voltammetric determination of Pb(II), Cd(II) and Zn(II) using an injection‐moulded electrochemical fluidic chip consisting of 3 conductive carbon fiber‐loaded polymer electrodes embedded in a plastic fluidic holder. The sample containing the target metals and a solution containing Bi(III) were aspirated in the holding coil of the SIA manifold. Then, the flow was reversed and the two solutions were directed to the fluidic cell through a mixing coil which induced mixing of the two zones. Upon reaching the cell, simultaneous reduction of the target metals and Bi(III) occurred resulting in the formation of a metal‐Bi alloy on the working electrode. Finally, the accumulated metals were stripped off the bismuth‐film electrode via a positive potential scan and the oxidation current was recorded. The experimental variables (concentration of the bismuth plating solution, deposition potential, sample volume, stripping mode) were investigated and the potential interferences were assessed. The limits of quantification were 2.8 μg L−1 for Pb(II), 3.6 μg L−1 for Cd(II) and 4.2 μg L−1 for Zn(II) and the the within‐chip and between‐chip % relative standard deviations were ≤6.3 % and ≤14 %, respectively. Finally, the sensor was applied to the determination of trace metals in a fish food sample. [ABSTRACT FROM AUTHOR]

Microalga biomass is considered as a potential feedstock for renewable energy owing to its high lipid content. Conventional microalgae cell culturing methods mostly require lengthy procedures and involve laborious and time-consuming steps. On the other hand, microalgae culturing in microfluidics offers several advantages over conventional methods, such as high sensitivity, enhanced mass and heat transfer, reduced runtime and cost, lower consumption of reagent, and better interaction of species. In this study, initially, a novel hybrid microfluidic differential carbonator (µ-DC) platform was constructed in-house. Then, the performance of this system was tested by microalgae culturing. In this regard, Picochlorum sp. was selected as a model microalgae cell due to its fast growth and high lipid content. The operating conditions for the microalgae growth were 2–6% (vol) inlet CO2 concentration, 49 µmole m2/s light intensity, and 1:0.025 inlet ratio of algae to media. Both spatial and temporal changes of the microalgae growth were investigated. A maximum microalgae growth after 45 h was found to be 3.37 × 10 10 cells/mL in a 50 µm depth cell culture (µ-CC), which is higher cell density than literature values. Such inflate of cell density can be attributed to the fact in improving the mass transfer and providing better contact of microalgae with the ingredients of the photosynthesis process. This remarkable improvement in the growth of cells is of significant importance for many applications, especially for biodiesel production. [ABSTRACT FROM AUTHOR]

This study investigates the effectiveness of a novel micro electrochemical flow-cell containing carbon fiber electrodes for the degradation of Azo dye solutions. The flow-cell was fabricated by an injection moulding technique, integrating three electrodes system design using an overmoulding procedure. All electrodes were fabricated from carbon fiber polymer, however, the reference electrode was then coated with Ag/AgCl paste. The effect of the process variables such as flow-rate, NaCl concentration, applied bias current, and solution pH on the degradation process were comprehensively studied. At optimum conditions, complete degradation of the dye was achieved on the bare carbon fiber electrode, without the need for surface modification, in 150 min upon the application of 15 mA bias current. The degradation process was suggested to follow the indirect oxidation mechanism where the presence of chlorine ions was very essential. Moreover, the micro-flow-cell had proven its stability over the entire operation time, which indicates its practicality for such on-line applications. [ABSTRACT FROM AUTHOR]

This work reports the development of a sequential injection/stripping analysis method for the determination of trace Pb(II) at injection-moulded electrochemical fluidic cells. Conducting carbon fibre–loaded polystyrene electrodes were integrated within the plastic cells. The flow-through cells were incorporated into a home-made sequential injection analysis (SIA) manifold. Different experimental parameters for the detection of Pb(II) were investigated including the type and concentration of the supporting electrolyte, the conditions of the stripping step, the volume of the sample, the flow rate and the accumulation potential. The LOD for Pb(II) was 0.5 μg L −1 , the within-cell % relative standard deviation ( n =8) was 3.1% and the between-cell % relative standard deviation ( n =5) was 8.9% for 25 μg L −1 Pb(II). The cells were applied to the determination of Pb(II) in tapwater and a phosphate fertilizer sample. [ABSTRACT FROM AUTHOR]

This study presents the degradation of methyl orange in a synthetic solution using an electro-oxidation technique. A novel polymer disk electrode was fabricated in this work using injection molding. Such an electrode is low cost, mass produced, and efficient to achieve a complete decolorization of methyl orange in the synthetic solution. The performance of the electrode was studied comprehensively. The degradation of methyl orange was accomplished in only 800 s. at optimum operating conditions of 0.1 M KCl electrolyte solution and constant applied current of 5 mA. The results revealed that the degradation of dye follows an indirect electro oxidation mechanism. It was also found that stirring is a crucial requirement to improve the mass transfer and to enhance the decolorization rate. The effect of changing the applied current, supporting electrolyte, electrolyte concentration, and initial dye concentration were also investigated. [ABSTRACT FROM AUTHOR]