Thermal aqueous liquid chromatography—the TALC technique

Thermal Aqueous Liquid Chromatography (TALC) using pure water as a mobile phase should be a very attractive technique promoting the use of liquid chromatography in routine analysis, either in the laboratory or in future on-line process control. This simple form of chromatography, the selectivity of which depends on the fixed phase only, would allow the use of flame ionization as an almost universal, low-cost detector in liquid chromatography. The potential of the TALC technique is illustrated by selected examples.     

Partial molar volumes of organic compounds in water. VI. α,ω-diaminoalkane hydrochlorides

Measurements of the partial molar volumes in water at 25°C of the mono-and dihydrochlorides of the ,-diaminoalkanes, up to a chain length of 10 carbon atoms, are reported. Volumes of ionization have been determined and the electrostriction of the solvent calculated. Effects of the substituents are felt up to the -carbon atom, but thereafter are only very weak or nonexistent.     

Quantum-chemical study of the interface formed by carboxylic species on TiO<Subscript>2</Subscript> nanoparticles. 1. Nanoparticle surface

The current paper presents results of a quantum-chemical study of the surface structure of nanoparticles of both rutile and anatase crystallographic modifications. Different stages of the surface relaxation are discussed. Water adsorption is considered. The calculations were performed in the spd-basis by using semi-empirical quantum-chemical codes, both sequential and parallel. The results are mainly addressed to the study of the interface formed by titania nanoparticles and a set of carboxylated species, namely, benzoic, bi-isonicotinic acids as well as tris-(2,2′-dcbipyridine) Fe(II) complex placed on the surface of either rutile or anatase polymorphs.This revised version was published online in August 2005 with a corrected issue number.     

Investigation of scattering of elastic waves by cylinders in 1-3 piezocomposites

The scattering behavior of P-waves in piezoelectric composites with 1–3 connectivity is studied. The method of wave function expansion is adopted for the theoretical derivations. Analytical expressions are obtained for the distributions of mechanical displacement in z-direction along the circumferences of piezoelectric cylinders. These solutions are used to study the influence of each element of the stiffness matrix and the piezoelectric matrix on the various resonant modes of vibration. Numerical results obtained indicate that perturbations of the elements c₄₄ and e₁₅ significantly affect resonant frequencies and amplitudes, perturbations of c₁₁ and c₁₂ have pronounced effects on resonant modes of high frequencies also. However, the resonant modes are not so sensitive to the perturbations of c₁₃, e₃₁ and e₃₃. The dynamic characteristics of 1–3 connectivity piezoelectric composites exposed here are meaningful for the design and manufacture of sensor/actuator elements by this kind of composites as well as the on-line health monitoring of the mechanical properties variations of the composites itself.     

Evolution of the Electroluminescence Spectra and the Acoustic Emission of the Epitaxial Structures of GaAsP

The dependence of the spectral position of the electroluminescence bands of epitaxial light-emitting diode n ⁺–n–p structures (GaAs_0.15P_0.85) on the density of a direct heterojunction current at different successive instants of time — before an acoustic emission and after it — has been revealed. The shifts of the electroluminescence bands accompanied by acoustic emission can be divided into three types according to the density of the current: (1) short-term shifts due to relaxation of the defect structure of a sample — at relatively low currents, (2) the magnitude of the reverse shift being determined by the current density — at large currents, and (3) formation of an IR band (1.5–1.1 eV) with irreversible degradation changing in the red (1.75 eV) and green (2.19 eV) bands of the electroluminescence spectrum — at ultrahigh currents (100–200 A/cm²).     

Radiative heat transfer analysis in pure water heater used for semiconductor processing

A simplified one-dimensional model is presented to analyze the non-gray radiative transfer in pure water heater used in the rinsing processes within semiconductor production lines, and the ray-tracing method is extended to simulate the radiative heat transfer. To examine the accuracy of the simplified model, the distribution of radiation absorption is determined by the ray-tracing method based the simplified model and compared with the data obtained by three-dimensional non-gray model in combination with Monte Carlo method in reference, and the effects of the water thickness on the radiation absorption are analyzed. The results show that the simplified model has a good accuracy in solving the radiation absorption in the pure water heater. The radiation absorption increases with the water thickness, but when the water thickness is greater than , the radiation absorption increases very slowly with the water thickness.     

Fluorimetric determination of aluminium in water by sequential injection through column extraction

A fluorimetric procedure for the determination of aluminium with matrix removal in drinking water is proposed. The system is based both on the solid phase extraction of aluminium on a new chelating resin (XAD-4 modified by grafting salicylic acid) and the fluorimetric detection of a complex formed between 8-hydroxyquinoline-5-sulfonic acid (HQS) and Al(III), after elution of the resin by hydrochloric acid. The sorption and elution of aluminium were studied in both competitive and non-competitive conditions, varying pH, flow-rates, volume and concentration of reagents, as well as time contact. The optimised procedure allows determination of Al³⁺ at the sub-ppb level (LOD: 0.2 g L^–1 for 1 ml of sample) within a working range of 0.2–500 g L^–1. The analytical procedure was successfully employed for the determination of aluminium in drinking water during and after flocculation/coagulation treatment processes.