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A coaxial flow-gating interface is described in which the separation capillary passes through the sampling capillary. Continuous flow of the sample solution flowing out of the sampling capillary is directed away from the injection end of the separation capillary by counter-current flow of the gating solution. During the injection, the flow of the gating solution is interrupted, so that a plug of solution is formed at the inlet into the separation capillary, from which the sample is hydrodynamically injected. Flow-gating interfaces are originally designed for on-line connection of capillary electrophoresis with analytical flow-through methods. The basic properties of the described coaxial flow-gating interface were obtained in a simplified arrangement in which a syringe pump with sample solution has substituted analytical flow-through method. Under the optimized conditions, the properties of the tested interface were determined by separation of K+, Ba2+, Na+, Mg2+ and Li+ ions in aqueous solution at equimolar concentrations of 50 μM. The repeatability of the migration times and peak areas evaluated for K+, Ba2+ and Li+ ions and expressed as relative standard deviation did not exceed 1.4%. The interface was used to determine lithium in mineral water and taurine in an energy drink. [ABSTRACT FROM AUTHOR]

A simple dual impedance tester has been designed for determining the water content in organic solvents. The detection cells are formed by a pair of semi-cylindrical electrodes of aluminium foil, located opposite one another around the outer surface of a glass tube with the tested solution. Thus, the electrodes are not in contact with the analysed solution. The detection cells are connected as a capacity determining the frequency of the integrated multivibrator. The analytical signal is the difference between the frequency of the multivibrator with the measuring cell filled with the analysed solution and the multivibrator with the cell filled with pure anhydrous solvent. Solvents with various permittivities and water contents to 50% v/v were tested, with a detection limit from 0.2% (dioxane) to 1.4% (acetonitrile). The method can also be used for determining the relative permittivity of solvents with various water contents. The detector can even be used outside the laboratory because it can be powered by a standard 9-V battery. [ABSTRACT FROM AUTHOR]

The paper provides a critical discussion of the present state of the theory of high-frequency impedance sensors (now mostly called contactless impedance or conductivity sensors), the principal approaches employed in designing impedance flow-through cells and their operational parameters. In addition to characterization of traditional types of impedance sensors, the article is concerned with the use of less common sensors, such as cells with wire electrodes or planar cells. There is a detailed discussion of the effect of the individual operational parameters (width and shape of the electrodes, detection gap, frequency and amplitude of the input signal) on the response of the detector. The most important problems to be resolved in coupling these devices with flow-through measurements in the liquid phase are also discussed. Examples are given of cell designs for continuous flow and flow-injection analyses and of detection systems for miniaturized liquid chromatography and capillary electrophoresis. New directions for the use of these sensors in molecular biology and chemical reactors and some directions for future development are outlined. [ABSTRACT FROM AUTHOR]

Abstract: A new ionic liquid–polymer electrolyte was successfully tested in the planar amperometric solid-state sensor sensitive towards nitrogen dioxide. The electrolyte consists of 1-butyl-3-methylimidazolium hexafluorophosphate (BMIPF6) and poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) in the ratio 57:43mol.% and exhibits ionic conductivity 1.6×10−4 Scm−1 at 20°C, high electrochemical stability (over 4V on gold or glassy carbon) and thermal stability (over 230°C). The analyte, gaseous nitrogen dioxide in air, was determined using the electrochemical reduction at −900mV vs. Pt/air on gold minigrid indicating electrode with Pt/air as a reference electrode. The sensor response is linear in the NO2 concentration range 0.3–1.1ppm and is reproducible and long-term stable. [Copyright &y& Elsevier]

The article focuses on the application of analytical chemistry in the area of capillary electrophoresis (CE) along short separation pathways. The study is designed to review the discipline of analytical chemistry in CE due to its reliability, ability to develop rapidly, and inexpensive analysis of complex samples. The study suggests that CE along with short separation pathway demonstrates a rapid, effective and reliable solutions of many analytical problems.

• On-line connection of capillary electrophoresis with midi-dialysis. • High speed separation by electrophoresis in short capillary. • Flow-gating interface with sampling space filled with air during injection. • Rapid sample preparation by digestion in hot acid. • Laboratory made portable analytical instrument with low first and operating cost. An analyser was constructed on the basis of on-line connection of capillary electrophoresis over a short separation path with continuous mini-dialysis sample collection. The developed instrument was employed for simultaneous determination of the majority minerals K+, Ca2+, Na+ and Mg2+ (and possibly NH 4 + ions) in commercially available unflavoured yoghurts. The cations are released from the organic structures by digestion with boiling 6 mol/L HCl. They were separated from residues of the organic matrix by a dialysis probe and were transferred to a stream of water. From the continuous stream, the dialysate was injected into the separation capillary through a flow-gating interface. Within the reliability interval, the determined total mineral content was equal to their contents stated on the yoghurt labels and the content determined by flame atomic absorption spectrometry and complexometric titration. The relative standard deviation of the electrophoretic determination is mostly about 5%. [ABSTRACT FROM AUTHOR]