Nanoporous platinum solid-state reference electrode with layer-by-layer polyelectrolyte junction for pH sensing chip

A novel solid-state reference electrode was developed by combining nanoporous Pt with polyelectrolyte junction. The polyelectrolyte junction was formed in the microchannel connecting the nanoporous Pt and the sample solution, and had layer-by-layer structure of oppositely charged polyelectrolytes. The layer-by-layer polyelectrolyte junction effectively blocked the mass transport of ions and maintains constant pH environments on the surface of the nanoporous Pt. The assembly of the polyelectrolyte junction and the nanoporous Pt, which produced reportedly a stable open-circuit potential in response to constant pH, exhibited outstanding performance as a solid-state reference electrode (e.g., excellent reproducibility of ±4 mV (n = 5), good long term stability of ±1 mV (for 50 h), and independence of solution environments like pH and ionic strength). A working principle of the solid-state reference electrode with layer-by-layer polyelectrolyte junction was suggested in terms of the roles of each layer and the effect of the neighboring layer. As a demonstrative application of the solid-state reference electrode, a miniaturized chip-type solid-state pH sensor comprised of two nanoporous Pt electrodes and a micro-patterned layer-by-layer polyelectrolyte junction was developed. The solid-state pH sensing chip showed reliable pH responses without liquid junction and successfully worked in a variety of buffers, beverages, and biological samples, showing its potential utility for practical applications. In addition, the solid-state pH sensing chip was integrated in a microfluidic system to be utilized for pH monitoring in microfluidic flow.     

Part mass and shrinkage in micro injection moulding: Statistical based optimisation using multiple quality criteria

Purpose

The aim of this paper is to optimise process conditions in micro injection moulding (μ−IM) to minimise shrinkage whilst maximising part mass.

Method

A Design of Experiment (DoE) approach was implemented for studying the effect of five processing parameters on shrinkage and part mass. A multiple quality criteria based analysis was used to optimise the process.

Results

Significant factors were found for shrinkage and part mass.

Conclusions

The multiple quality criteria could be optimized, and this optimization validated experimentally.     

The prediction of mechanical properties of injection moulding parts by vacuum casting

The behaviour of vacuum cast prototypes and injection moulding parts in mechanical tests was compared. The mechanical tests were made using real production parts as references. Distinct correlations were found between vacuum cast prototypes and injection moulding parts. In this light, vacuum cast prototypes can be used for the evaluation of injection moulding products with certain limitations. Vacuum casting is best suited for the evaluation of such mechanical properties of injection moulding products as tensile, flexural and compression strength, while impact strength is the property that is most difficult to evaluate.     

Flame retarded self‐reinforced polypropylene composites prepared by injection moulding

A method was elaborated to prepare flame retarded self‐reinforced polypropylene composites by injection moulding. The effect of intumescent flame retardant (FR) loading was comprehensively investigated on the morphology, flammability, and mechanical properties of the self‐reinforced polypropylene composites and compared with non‐reinforced counterparts of identical additive contents. Homogeneous distribution of both the reinforcing polypropylene fibres and the FR additive was achieved endowing significantly improved strength and stiffness accompanied with increased fire resistance. At 10% FR content, 37% reduction of peak of heat release rate, UL94 V‐2 rating, and LOI of 24.5 vol% were achieved without compromising the improved mechanical performance of the injection moulded self‐reinforced composites, ie, a 4‐fold increase of tensile strength and a 7‐fold increase of tensile modulus were reached compared with the non‐reinforced counterpart. At higher loading (15% FR), the FR properties improved further (LOI of 29.5 vol% was reached); however, due to the abrasive effect of the FR particles in the matrix, the structure of the reinforcing fibres tends to get damaged during the thermo‐mechanical processing, and thus their reinforcing efficacy deteriorated. It is demonstrated that the combination of polymer fibre reinforcement with other fillers (such as FRs) is advantageous and feasible even by injection moulding, but the balance between the individual attributed properties needs to be found.     

Flow-through tubular PVC matrix membrane electrode without inner reference solution for flow injection analysis

A simply constructed tubular PVC matrix membrane electrode without inner reference solution suitable for flow injection analysis is described. The nitrate-selective electrode developed allows simple replacement of an exhausted membrane, or change of function with a new sensor membrane. The compact design ensures mechanical stability and the tubular configuration minimizes distortion of the hydrodynamic flow in the detector. Nitrate can be determined in the range 10^?1–10^?5 M, under different flow conditions, with a sampling frequency of about 120 h^?1.     

Selectrode—the universal ion-selective electrode : Part VII. A valinomycin-based potassium electrode with nonporous polymer membrane and solid-state inner reference system

A potassium electrode utilizing a solution of valinomycin in diphenylether and a porous membrane is compared with selectrodes in which the diphenylether has been replaced by a suitable plasticizer and the porous membrane support by a polymer net-work. The development of the polymer membrane allows the use of simplified selectrode construction with a “solid-state” calomel reference system; Rules for a successful choice of a suitable solvent-polymer combination are suggested and used for development of new Polyvinylchloride- and polyurethane-based membranes.     

Flow injection determination of ergonovine maleate with amperometric detection at the Kel-F-graphite composite electrode

The Kel-F-graphite electrode was used for the electrochemical detection of ergonovine maleate in a flowing stream. It was found useful in the analyte concentration range 0.5-20 mug ml , with a detection limit of 50 ng ml (1.1 x 10(-7)M). A procedure was developed for assay of ergonovine maleate in tablets, and the results obtained agreed with those given by the official U.S. Pharmacopeia method.     

Analytical quality control by solid sampling GFAAS in the production of animal tissue reference materials: lead and cadmium in bovine liver reference materials

Summary The function of solid sampling graphite furnace atomic absorption spectrometry (SS-GFAAS) in the laboratory-internal preparation, production and standardization of bovine liver reference material is described. Analytical quality assurance was achieved by using a wet digestion decomposition procedure and GFAAS (WD-GFAAS) as well as three different methods of SS-GFAAS. It will be shown, that SS-GFAAS is an adequate and efficacious method of analytical quality control in the production of reference materials. Details are given about the preliminary steps of sample selection and preparation, applying SS-GFAAS both as a screening method and for the detection of contamination during the production of the reference materials. The element contents of the four bovine liver materials measured after decomposition with nitric acid in the open system by GFAAS and also by Flame-AAS, using the slotted tube atom trap, are compared statistically with the results obtained by SS-GFAAS. In solid sampling analyses three different systems were applied: a solid sampling ZAA-spectrometer with platform-boat, a D₂AA-spectrometer with solid sampling graphite tube and platform-drawer and an autoprobe-D₂AA-spectrometer with solid sampling autoprobe and graphite tube.     

Analytical problem-solving, reference materials, and multivariate quality control: A chemometrics approach

Summary Breakthroughs in sensor technology have augmented the chemist's measurement repertoire by introducing new kinds of detectors with improved selectivity and the capacity to perform simultaneous multi-species measurements. Thus, the electronic revolution has qualitatively and quantitatively changed the data matrices to which the analyst/problem-solver has access. The new chemical subdiscipline of chemometrics is developing powerful mathematical and statistical data analysis tools to exploit the electronic windfall and enhance data interpretation. Principal component analysis and graphical procedures have been used to examine the multivariate suitability of current reference materials in matching the concentration ranges and matrices for various food analyses. Principal component analysis has been useful in developing and exploring quality control information for the routine analysis laboratory.     

Reducing the void content and its variability in polymeric fibre reinforced composite test specimens using a vacuum injection moulding process

To obtain acceptable accuracy and consistency in the mechanical testing of polymeric fibre reinforced composities, it is important that both the fibre alignment and the void content be precisely controlled. In particular, a high void content can greatly affect both the variability and the value of the mechanical strengths of the composite. This paper describes the use of a simple vacuum injection moulding process to produce fibre reinforced composites that have a consistently low void content, of about 1·3%, and a correspondingly high and consistent flexural strength.     

High performance poly (vinyl alcohol)/cellulose nanocrystals nanocomposites manufactured by injection molding

Polyvinyl alcohol (PVA)/cellulose nanocrystals (CNCs) compounds were successfully melt-processed by injection molding. During the processing, water was involved in the system as both the dispersion medium for CNCs and the plasticizer for PVA. Meanwhile, formamide was added to prevent the evaporation of water and to co-plasticize PVA. Thermal gravimetric analysis and differential scanning calorimetry indicated the melt processing window of PVA was expanded by 40 °C. Tensile tests showed that the mechanical properties of injection-molded samples were significantly improved with the addition of CNCs. The tensile strength of the composites increased from 32 to 58 MPa, and modulus increased from 175 to 1,252 MPa when 7 wt% CNCs was added. Moreover, the volume shrinkage of PVA nanocomposites upon drying as well as their water leaching rate could be remarkably reduced in the presence of CNCs.     

Flow injection analysis of ethambutol in synthetic urine using a graphite-polyurethane composite electrode as an amperometric detector

Ethambutol (ETB) is a first-line antitubercular drug effective against actively growing Mycobacterium tuberculosis. Resistance of the mycobacterium to ethambutol among tuberculosis (TB) patients results from inadequate or inappropriate dosing of treatment or using low quality medication. It is therefore necessary to develop reliable methods for determining ethambutol metabolic profiles of patients at point of care for proper dosing. Herein an efficient ETB sensor device is illustrated. It consists of a graphite-polyurethane composite electrode. In order to characterise the electrochemical behaviour of ethambutol at pH = 8.0 voltammetric studies were performed. The detector was assembled in a flow injection apparatus and operated at +1.2 V (vs. Ag/AgCl(NaCl sat.)). The influence of sample volume and flow rate was studied. The linear response for the method was extended up to a 1.1 mmol L^?1 ethambutol solution with a detection limit of 0.0634 mmol L^?1. The reproducibility of current responses for injections of 0.7 mmol L^?1 ethambutol solution was evaluated to be 5.1% (n = 30) and the analytical frequency was 161 determinations h^?1. Two different samples were successfully analysed and the results were in good agreement with those obtained using capillary zone electrophoresis (CZE).      

Parameter-independent error correction for potential measurements by reference electrode in lithium-ion batteries

The safety monitoring of lithium-ion batteries(LIBs) is of great significance for realizing all-climate and full-lifespan battery management. In-situ measurement of anode potential with implanted reference electrodes(REs) has proven to be effective to monitor and avoid the occurrence of severe side reactions like Li plating to ensure the safe and fast charging. However, the intrinsic measurement errors caused by local blocking effects, which also can be referred to as potential artefacts, are se...     

固态碳糊电极电位法测定利多卡因注射液

本文报道了一种以利多卡因与单质碘形成的缔合物为电活性物的全固态碳糊利多卡因电极,电极的线性响应范围5.0×10-2～4.0×10-5mol.L-1,级差电位为30mV/pC,检测下限为3.0×10-5mol.L-1。该电极响应迅速,重现性好,用该电极测定了盐酸利多卡因注射液中利多卡因的含量,结果与药典法相符。     

Carbon-nanotube-alginate composite modified electrode fabricated by in situ gelation for capillary electrophoresis

This report describes the development and the application of a novel carbon-nanotube (CNT)-alginate composite modified electrode as a sensitive amperometric detector for capillary electrophoresis (CE). The composite electrode was fabricated on the basis of in situ gelation of a mixture of CNTs and sodium alginate on the surface of a carbon disc electrode in aqueous calcium chloride solution. SEM, energy-dispersive spectroscopy, XRD, and FTIR spectroscopy offered insights into the nature of the novel composite. The results indicated that the CNTs were well dispersed and embedded throughout the alginate matrix to form an interconnected carbon-nanotube network on the base electrode. The performance of this unique CNT-based detector has been demonstrated, in conjunction with CE, by separating and detecting five caffeic acid derivatives. The new CNT-based CE detector offered significantly lower operating potentials, substantially enhanced signal-to-noise characteristics, and a lower expense of operation. The simplicity and significant performance exhibited by the CNT-alginate composite modified electrode also indicate great promise for the use of this electrode in microchip CE, flowing-injection analysis, and other microfluidic analysis systems.     

Understanding the interfacial region in organic ionic plastic crystal composite electrolyte materials by solid-state NMR

Organic ionic plastic crystal composites exhibit properties that make them suitable for many applications including energy storage devices and CO₂ separation. In most cases, the mixing of organic ionic plastic crystals with a polymer, salt or a porous material leads to the formation of interfacial regions that can enhance the ion transport of desired ions like Li⁺ for battery applications. The study of these interfacial regions is challenging and requires the use of spectroscopic techniques like solid-state NMR to characterise the structure, interactions, and ion dynamics. This article summarises the advantages and challenges of organic ionic plastic crystals and their composites, and the common NMR methods used to study the interfacial regions between their components.     

Potentiometric detection of monovalent anions separated by ion chromatography using all solid-state contact PVC matrix membrane electrode

Summary An all solid-state contact tubular PVC-matrix membrane electrode has been applied for potentiometric detection of inorganic and organic monovalent anions using phosphate and hydrogen phosphate eluents at low concentrations. This is a “monovalent detection method” as the selectivity of the electrode towards monovalent anions results in some other anions being undetected unless the concentration of those other anions is higher than 10⁻³ mol dm⁻³ in the sample solution injected. It takes only eight minutes to complete the separation with a good resolution. Theoretical and practical considerations are discussed, and in particular, sensitivity, linearity, detection limit and dynamic behaviour are presented. The use of an all solid-state contact bromide-selective electrode as a detector offers so far the best simultaneous sensitivity toward all anions when compared with other detection methods. Determination of Cl⁻ and NO₃ ⁻ ions in river, rain and drinking water samples without any further sample preconcentration has been successfully achieved. The detection limit is sub-ppb for most of anions in a 20 μL injection volume.     

The formation and properties of acrylic‐polyurea interpenetrating networks formed by reaction injection moulding (RIM)

Interpenetrating networks (IPNs), comprising a crosslinked acrylic as one component and either a rubbery copoly(ether‐urea) or a glassy copoly(urea‐isocyanurate) as the other component, have been formed by reaction injection moulding (RIM). Reaction kinetics during RIM processing of the IPNs were studied using adiabatic temperature rise (ATR) measurements. The effects of (i) crosslinker concentration in the acrylic component and (ii) the weight fraction of acrylic, on the formation of the IPNs during RIM and on the dynamic mechanical properties of finally‐formed IPNS, were evaluated. The results are interpreted in terms of differences in the rates of polymerisation and in the solubilities of the acrylic‐ and polyurea‐forming components, and of the phase‐separated structures of the IPNs.