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A cyclodextrin-based polymer was prepared by crosslinking β-cyclodextrin with epichlorohydrin to be assessed as a sorbent material for cresols in packed-bed columns. Both Langmuir and Freundlich isotherms were appropriate to describe the sorption equilibrium in the conditions tested, and the thermodynamic parameters obtained for this process confirmed its exothermic nature with similar enthalpies (between − 6.8 and − 8.3 kJ/mol) for the three isomers. The removal of cresols from water was carried out in nine cycles of sorption–desorption in fixed-column experiments with the cyclodextrin hydrogel, achieving sorption capacities of 6.2, 11.6, and 15.1 mg/g for o-, m-, p-cresol, respectively. These differences in sorption capacities are due to the different chemical structures of cresols, that is, the relative position of the methyl and hydroxyl groups. However, similar sorption rates were observed for each isomer, with a mean value of 0.10 mg-cresol g-CDP–1 min–1 in all cases. The experimental data for the breakthrough and the elution curves have been successfully modeled by two effective two-parameter equations, a dose–response model for the sorption step and a pulse-peak model for the regeneration step. The cyclodextrin polymer matrix has been proven to be an effective a good sorbent material for removing cresols from water, exhibiting remarkable reusability performance and structural stability throughout the successive elution steps carried out with methanol. [ABSTRACT FROM AUTHOR]

BACKGROUND Determination of strontium (Sr) and neodymium (Nd) isotopic composition in geological samples by Multi-collector Inductively Coupled Plasma-Mass Spectrometry (MC-ICP-MS) needs a lengthy and complex chemical preparation procedure. Moreover, samples cannot be dissolved completely. OBJECTIVES To effectively digest samples and eliminate interferences from the experimental process. METHODS Geological samples were dissolved by microwave digestion. The processes of Sr, Nd chemical separation and mass spectrometry analyses were studied. In particular, the recovery and memory effect of resin column were investigated. RESULTS The research shows that after ten times usages Sr and Nd procedure, blanks of the resin are less than 1.0 ng. However, the recovery decreases significantly from 98% to 20% and 90% to 50%, respectively. If the analyzed samples contain low concentrations of Sr and Nd, which are insufficient for mass spectrometry analysis, it is suggested that Sr special effect resin should be used no more than 5 times and AG50W-X8 and Ln resin should be used no more than 10 times. The entire procedure is applied in the separation of Sr and Nd of international standard geological samples (BCR-2, W-2a, BHVO-2, AGV-2). The acquired 87Sr/86Sr and 143Nd/144Nd ratios are consistent with those in the literature, and the instrumental internal precision 2SE (n=50) and methodological external precision 2SD (n=6) are better than 0.0015%. CONCLUSIONS The proposed method meets the requirement of high-precision measurement of Sr and Nd isotopic composition in geological samples.

BACKGROUND: Determination of strontium( Sr) and neodymium( Nd) isotopic composition in geological samples by Multi-collector Inductively Coupled Plasma-Mass Spectrometry( MC-ICP-MS) needs a lengthy and complex chemical preparation procedure. Moreover,samples cannot be dissolved completely.OBJECTIVES: To effectively digest samples and eliminate interferences from the experimental process.METHODS: Geological samples were dissolved by microwave digestion. The processes of Sr,Nd chemical separation and mass spectrometry analyses were studied. In particular,the recovery and memory effect of resin column were investigated.RESULTS: The research shows that after ten times usages Sr and Nd procedure,blanks of the resin are less than1. 0 ng. However,the recovery decreases significantly from 98% to 20% and 90% to 50%,respectively. If the analyzed samples contain low concentrations of Sr and Nd,which are insufficient for mass spectrometry analysis,it is suggested that Sr special effect resin should be used no more than 5 times and AG50 W-X8 and Ln resin should be used no more than 10 times. The entire procedure is applied in the separation of Sr and Nd of international standard geological samples( BCR-2,W-2 a,BHVO-2,AGV-2). The acquired87 Sr/86 Sr and143 Nd/144 Nd ratios are consistent with those in the literature,and the instrumental internal precision 2 SE( n = 50) and methodological external precision 2 SD( n = 6) are better than 0. 0015%.CONCLUSIONS: The proposed method meets the requirement of high-precision measurement of Sr and Nd isotopic composition in geological samples. [ABSTRACT FROM AUTHOR]

Abstract: A set of accurate expressions of elution-curve moments are derived from the moments of residence time and displacement in a step based on probability theory. Then the problems about residence time and displacement in a step of a solute molecule in the porous layer of capillary columns and in the moving mobile phase are described by a set of mass-balance equations respectively. The set of equations are solved in Fourier–Laplace domain, and the characteristic functions of residence time of a step, as well as the moments, are obtained by means of computing software Mathematica. At last, using numerical inverse Laplace transform, the elution curves for various conditions are calculated. In the case of large desorption constant the results entirely coincide with those of mass-balance-equation theory and in the case of small desorption constant they are equivalent to those of stochastic theory. [Copyright &y& Elsevier]

Abstract: Based on the mass-balance principle, a particular diffusion equation to describe the movement of solute molecules in the stagnant layer of multiple-site solid surfaces is constructed. From the equation, the moments of residence time in a step on multiple-site surfaces are derived. Similarly, the moments in a step in the mobile phase are also derived from a diffusion-drift equation. According to the probability theory, there exists a general relationship between the moments of an elution curve and the moments in a step. Through this relationship, the expressions of the elution-curve moments are derived from the step moments. In this paper, the details related to multiple-site linear wall-adsorption capillary chromatography are described and added in the equations to determine the step moments. The resultant expressions of the elution-curve moments involve various factors, such as adsorption–desorption rate constants, equilibrium constants, axial and radial dispersions in the mobile phase. Afterwards, the moment expressions are used to analyze the peak tailing. The results show that a small quantity of sites with a slow desorption rate will lead to a large peak asymmetry. [Copyright &y& Elsevier]

A two-stage method is described for the purification of Cu radionuclides from up to 5 g of natZn and other radionuclides. After proton bombardment, co-produced 66,67Ga is removed by passing the dissolved zinc in 7 M HCl through a 2.5 ml column of AmberChrom CG-71, a methacrylate-based polymeric resin. This first column eluate, which contains 65Zn, 64,67Cu, and 56,57,58Co, is taken to incipient dryness and reconstituted in 300 ml 0.05 M HCl. This solution is then pumped through a novel 10 ml column of dithizone impregnated AmberChrom CG-71, where Cu radionuclides are efficiently retained with no breakthrough. Zinc and Co radionuclides elute smoothly during washing with no tailing. More than 97 % Cu is eluted by washing with 40 ml 5 M HNO3 warmed to 50 °C. No dithizone is detected in this eluate. [ABSTRACT FROM AUTHOR]

A mathematical model is developed for fixed-beds packed with inert core adsorbents. New analytical solutions to predict breakthrough and elution curves are derived for linear adsorption systems coupled with axial dispersion, film mass transfer and intraparticle mass transfer. New approximate solutions are also obtained based on the assumptions of parabolic concentration profile in the adsorbent shell and the quasi-lognormal distribution for the impulse response in order to predict breakthrough and elution curves. The applicability of these approximate solutions is suggested by comparison with the new analytical solutions. The effects of the size of inert core, sample input mode, axial dispersion, film mass transfer resistance and intraparticle diffusion resistance, on the breakthrough and elution curves are discussed. The decrease of the intraparticle mass transfer resistance by using inert core adsorbents is quantitatively analyzed by introducing the parameter 1/Θ. Furthermore, an analytical expression for the resolution of two components is derived based on the quasi-lognormal distribution approximate solution; the resolution of two components is improved with the inert core adsorbent when compared with the conventional adsorbent, especially for biomacromolecules where the intraparticle diffusion rate is slow. [Copyright &y& Elsevier]

99Mo was produced by the 100Mo(n, 2n) 99Mo reaction using 14-MeV neutrons from the D(³H, n)4 He reaction at Fusion Neutronics Source Facility (FNS) at JAEA. A target of titanium oxide gel with molybdenum oxide was irradiated and used as the 99mTc/99Mo generator. The growth curve of 99mTc in the titanium gel target and the elution curve of 99mTc from the 99Mo/99mTc generator were obtained. [ABSTRACT FROM AUTHOR]