Separation and determination of some carboxylic acids by capillary electrophoresis

RADIOCHSeparation and determination of some organic acids, mono-carboxylic (formic and acetic), dicarboxylic (oxalic and tartaric), tricarboxylic (citric) acids and aromatic acids (phtalic, benzoic, mellitic and trimellitic), by capillary electrophoresis are reviewed. The method development parameters, such as separation and injection mode, are discussed. Special attention is paid to the comparison of different detection types (spectroscopic and electrochemical). The optimisation of the carrier electrolyte composition (choice of carrier electrolyte, effect of pH, ionic strength, electro-osmotic flow modifier) is treated. Different additives (alkali-earth and transition metal ions, cyclodextrins and alcohol), which are often used for improving organic acid separation, are also considered

Large cone angle magnetization precession of an individual nanomagnet with dc electrical detection

We demonstrate on-chip resonant driving of large cone-angle magnetization precession of an individual nanoscale permalloy element. Strong driving is realized by locating the element in close proximity to the shorted end of a coplanar strip waveguide, which generates a microwave magnetic field. We used a microwave frequency modulation method to accurately measure resonant changes of the dc anisotropic magnetoresistance. Precession cone angles up to $9^{0}$ are determined with better than one degree of resolution. The resonance peak shape is well-described by the Landau-Lifshitz-Gilbert equation

On-chip detection of ferromagnetic resonance of a single submicron permalloy strip

We measured ferromagnetic resonance of a single submicron ferromagnetic strip, embedded in an on-chip microwave transmission line device. The method used is based on detection of the oscillating magnetic flux due to the magnetization dynamics, with an inductive pick-up loop. The dependence of the resonance frequency on applied static magnetic field agrees very well with the Kittel formula, demonstrating that the uniform magnetization precession mode is being driven

Electrical detection of spin pumping due to the precessing magnetization of a single ferromagnet

We report direct electrical detection of spin pumping, using a lateral normal metal/ferromagnet/normal metal device, where a single ferromagnet in ferromagnetic resonance pumps spin polarized electrons into the normal metal, resulting in spin accumulation. The resulting backflow of spin current into the ferromagnet generates a d.c. voltage due to the spin dependent conductivities of the ferromagnet. By comparing different contact materials (Al and /or Pt), we find, in agreement with theory, that the spin related properties of the normal metal dictate the magnitude of the d.c. voltage

Uranyl complexation with selenate at variable temperatures studied by affinity capillary electrophoresis

The uranyl-selenate system is studied in aqueous acid solutions (pH 2.5) at different values of the ionic strength (from 0.02 to 0.1 mol L−1) in the temperature range from 15 °C to 55 °C by affinity capillary electrophoresis. Hydrodynamic transfer of the sample through the non-thermostated inlet into the thermostated region of capillary is used to avoid the influence of non efficiently thermostated short inlet. The formation of two complex species UO2SeO4 and UO2(SeO4)22− is observed. Thermodynamic parameters (the molar Gibbs energy of reaction (ΔrGm), the molar enthalpy of reaction (ΔrHm) and the molar entropy of reaction (ΔrSm)) are calculated and extrapolated to zero ionic strength with aid of specific ion interaction theory. Results show that complex species of uranyl with selenate become stronger as the temperature is increased. The complexation is endothermic and entropy-driven, showing typical characteristics of inner-sphere complexation between hard acceptor and hard donor

Interaction of uranyl with acetate in aqueous solutions at variable temperatures

Increasing activities in the environmental management of nuclear wastes incite significant interest in the study of the interaction of actinides with organic matter in aqueous solution, especially at elevated temperature. The system U(VI)-acetic acid is studied in aqueous solutions at pH 2 in the temperature range from 15 °C to 55 °C by affinity capillary electrophoresis (ACE). The formation of two complex species UO2CH3COO+ and UO2(CH3COO)2 is observed. Thermodynamic parameters (the molar Gibbs energy of reaction (ΔrGm), the molar enthalpy of reaction (ΔrHm) and the molar entropy of reaction (ΔrSm)) are determined at fixed ionic strength of 0.05 mol * L−1 (NaClO4-HClO4) and calculated at 0 ionic strength with extended Debye-Hückel equation for the activity coefficients. Obtained results are compared with literature data

Effect of non-thermostated capillary inlet in affinity capillary electrophoresis: Uranyl-selenate system at variable temperatures

The influence of non-thermostated capillary inlet on accuracy of data obtained by affinity capillary electrophoresis is examined in the case of kinetically labile systems (with fast kinetics of equilibrium) at different temperatures. The system uranyl-selenate is studied in aqueous perchloric acid solutions (pH 2.5, ionic strength 0.05 mol l−1) in the temperature range from 15 °C to 55 °C. Moving of the sample through the non-thermostated inlet into the thermostated region of the capillary is used in order to avoid the influence of non efficiently thermostated short capillary inlet. The data on mobility values of uranyl and the values of stability constants obtained by this mode are compared with the data obtained in a traditionally used mode (injection in non-thermostated inlet region). The uranyl mobility values obtained by the two methods are different at temperature higher than 35 °C. However, the difference between stability constants obtained by the two methods is not significant (ambient temperature is 20 °C)