Conductivity of weak electrolytes for buffer solutions: Modeling within the mean spherical approximation

International audienceThe purpose of this study is to predict the electrical conductivity of some weak electrolytes used in buffer solutions. The acid-base reactions occurring between the different species in solution are evaluated taking into account the activity coefficients. The deviations from ideality necessary to describe the equilibrium and transport properties are estimated within the mean spherical approximation (MSA). Results from theoretical expressions of the conductivity of electrolyte mixtures are compared with experimental results from the literature in the case of acetate, carbonate and bicarbonate solutions. In order to characterize all the ions that may be present, we also studied the ability of our theory to describe some strong alkaline or acid solutions

Peak asymmetry understanding in α\alpha liquid scintillation with β\beta/γ\gamma rejection

The alpha liquid scintillation with / discrimination is an analytical method of interest for the determination of emitters at the trace level. Several authors already suggested its utilization for the detection of radioactivity in environmental samples due to its high sensitivity and a fast sample preparation. Nevertheless, whatever the apparatus used, it suffers a dramatic lack of resolution in comparison with the spectrometry in a grid chamber or with PIPS detectors. The peak shape is often considered nearly Gaussian, which greatly simplifies the deconvolution process (reduction of the number of variables), even for complex spectra. This assertion is quite acceptable for very low activity measurements but can not be applied for measurements using spike standardization. Thus, it became necessary to understand why the asymmetry factor is an intrinsic property for each nuclide

Peak asymmetry understanding in α\alpha liquid scintillation with β\beta/γ\gamma rejection

The alpha liquid scintillation with / discrimination is an analytical method of interest for the determination of emitters at the trace level. Several authors already suggested its utilization for the detection of radioactivity in environmental samples due to its high sensitivity and a fast sample preparation. Nevertheless, whatever the apparatus used, it suffers a dramatic lack of resolution in comparison with the spectrometry in a grid chamber or with PIPS detectors. The peak shape is often considered nearly Gaussian, which greatly simplifies the deconvolution process (reduction of the number of variables), even for complex spectra. This assertion is quite acceptable for very low activity measurements but can not be applied for measurements using spike standardization. Thus, it became necessary to understand why the asymmetry factor is an intrinsic property for each nuclide

Conductivity of weak electrolytes for buffer solutions: Modeling within the mean spherical approximation

International audienceThe purpose of this study is to predict the electrical conductivity of some weak electrolytes used in buffer solutions. The acid-base reactions occurring between the different species in solution are evaluated taking into account the activity coefficients. The deviations from ideality necessary to describe the equilibrium and transport properties are estimated within the mean spherical approximation (MSA). Results from theoretical expressions of the conductivity of electrolyte mixtures are compared with experimental results from the literature in the case of acetate, carbonate and bicarbonate solutions. In order to characterize all the ions that may be present, we also studied the ability of our theory to describe some strong alkaline or acid solutions

Selective determination of polonium by photon electron rejecting alpha liquid scintillation (PERALS (R) System)

We developed a fast analysis method for the determination of polonium by alpha liquid scintillation with beta-gamma rejection in environmental samples. The liquid-liquid extraction with several extractants like HDEHP, TNOA, TOPO or NDA was applied. Among them, the use of the trioctylamine (TNOA) allows the separation of polonium from uranium, plutonium and thorium in a mixture containing 3 M H2SO4 and sodium chloride (2 x 10(-2) to 1 M). The distribution ratio of polonium is over 10(4), whereas it is only equal to about 10(-1) for U, 3 x 10(-2) for Th, and 3 x 10(-3) for Pu. This separation process was applied with success to large volume of aqueous solution (250 ml). The detection limit is below 1 mBq l(-1) for 200 ml of solution and for a counting time equal to 1000 min. We also successfully applied this procedure for the polonium activity measurement in various colorless aqueous solutions.Several difficulties were encountered by using this method to organic matter such as fish or shellfish. A yellow coloration occurs which does not allow a measurement. Moreover, the volatility of polonium compounds unables the use of conventional dissolution methods for organic matter. These problems are also discussed in this paper