Thiocyanate and nitrite analysis using miniaturised isotachophoresis on a planar polymer chip

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.     

Rheological properties of poly(2,6-dimethylphenylene oxide)—polystyrene blends

The viscoelastic (VE) response of freeze-dried blends of polystyrene (PS) and poly-(2,6-dimethyl phenylene oxide) (PPO) has been studied as a function of composition, frequency, and temperature to examine the degree of rheological compatibility. When blended together, the relaxation processes of both molecular species exhibit the same temperature dependence. However, the temperature dependence of the VE response is a function of composition. It is shown that this behavior can be predicted from the measured glass transition temperatures by assuming the additivity of the free volumes of the components. The properties of the blends are compared at equal free volumes. The effective segmental friction factor is found to be independent of composition while the modulus of the rubbery plateau increases with PPO concentration. This result is interpreted as a change in the entanglement molecular weight M_e of the blends. When the changes in M_e are considered, the relationship between the zero-shear viscosity η0 and the 3.4 power of the weight-average molecular weight, commonly found for high molecular weight homopolymers, predicts the compositional dependence of η0 for the PPO–PS blends. It is concluded that the PPO–PS system forms a rheologically compatible blend.     

Krull–Gabriel Dimension of 1-domestic String Algebras

We classify the indecomposable pure injective modules over a wide class of -domestic string algebras and calculate the Krull–Gabriel dimension of these algebras.This paper was written during the visit of the second author to the University of Manchester supported by EPSRC grant GR/R44942/01.     

The simultaneous determination of chloride, nitrate and sulphate by isotachophoresis using bromide as a leading ion

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 1.25 mM indium(III) at pH 3.15 and a terminating electrolyte of cyanoacetic acid.     

Use of miniaturised isotachophoresis on a planar polymer chip to analyse transition metal ions in solutions from metal processing plants

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 0.5-1.0mg l(-1) for Mn2+, Cr3+ Co2+ and Zn2+ and 2.0 mg l(-1) for Fe2+ and 4.7 mg l(-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 13 min. The separations were performed on a poly(methyl methacrylate) chip with integrated platinum wire conductivity detection electrodes.     

Miniaturised isotachophoresis analysis

The application of miniaturized total analysis systems (microTAS) has seen rapid development over the past few years. Isotachophoresis (ITP) has been transferred into microchip format for both electrophoretic separation and pretreatment purposes, due to its advantageous features including separation parameters controlled by electrolyte composition and high sample load capacity. The primary focus of this concise review is to summarize the basic features of microchip based ITP and its applications to the analysis and pretreatment of ionic compounds and biomolecules that have arisen since 1998.