The role of salts derived from benzilic acid and quinolines in the adsorption of some actinides Part I: Characterization of the adsorbers

The salt of the 8-hydroxyquinoline and benzilic (diphenylglycolic) acid was prepared and incorporated into active charcoal in order to have an adsorber able to concentrate actinides dispersed in natural waters before quantitative or radiochemical analysis. The formation and the characterization of this adsorber, (adsorber B), was compared with another system containing benzilic salt of the substituted quinoline, 2-methyl, 8-hydroxyquinoline, (adsorber R). The adsorption ability of the adsorbers B and R was compared with a third product (adsorber G), prepared by incorporating benzilic acid with d-glucosamine into the charcoal. In this case, d-glucosamine gives a better stability to the system, as otherwise the benzilic acid could partially be dissolved into the water system at equilibrium, during the adsorption experiments. The dissociation acid constants of all the considered components were measured, in order to have some information on the adsorption mechanism. The compound formed during the adsorption on the prepared adsorbers with uranium, thorium, and samarium were separately analyzed and identified by means of IR and NMR. The role of the components in the adsorption was evidenced. This revised version was published online in July 2006 with corrections to the Cover Date.     

Quasiclassical trajectory calculations to evaluate a kinematic constraint on internal energy in suprathreshold collision energy abstraction reactions

Experimentally observed product quantum state distributions across a wide range of abstraction reactions at suprathreshold collision energies have shown a strong bias against product internal energy. Only a fraction, sometimes quite a small fraction, of the energetically accessible product quantum states are populated. Picconatto et al. [J. Chem. Phys. 114, 1663 (2001)] noted a simple mathematical relationship between the highest-energy rovibrational states observed and the kinematics of the reaction system. They proposed a reaction model based on reaction kinematics that quantitatively explains this behavior. The model is in excellent agreement with measured quantum state distributions. The assumptions of the model invoke detailed characteristics of reactive trajectories at suprathreshold collision energies. Here we test those assumptions using quasiclassical trajectory calculations for the abstraction reactions H+HCl-->H2+Cl, D+HCl-->HD+Cl, and H+DCl-->HD+Cl. Trajectories were run on a potential-energy surface calculated with a London-Eyring-Polyani-Sato function with a localized 3-center term (LEPS-3C) previously shown to accurately reproduce experimentally observed product state distributions for the H+HCl abstraction reaction. The trajectories sample collision energies near threshold and also substantially above it. Although the trajectories demonstrate some aspects of the model, they show that it is not valid. However, the inadequacy of the proposed model does not invalidate the apparent kinematic basis of the observed energy constraint. The present results show that there must be some other molecular behavior rooted in the reaction kinematics that is the explanation and the source of the constraint.     

Electrochemical ELISA for the screening of DDT related compounds: analysis in waste waters

An electrochemical enzyme-linked immunosorbent assay (ELISA) for the detection of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (p,p′-DTT), 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p′-DDE), 1,1-dichloro-2,2-bis-(4-chlorophenyl)ethane (p,p′-DDD) and o,p-DDT was developed. Optimization of the ELISA competition conditions, led to similar response for the p,p′-isomers. The activity of the label enzyme (horseradish peroxidase) was measured electrochemically using 3,3′,5,5′-tetramethylbenzidine as substrate. The use of purified antiserum for p,p′-DDT resulted in a sensitive assay with a detection limit of 40 pg ml⁻¹ and R.S.D. ranging from 1 to 3% intra-day and 3 to 6% inter-day. No matrix effect for waste water samples of different origin has been evidenced. The ELISA was used to detect DDTs in 20 samples after extraction in diethylether. This method appears suitable for routine screening of DDTs without sample pre-treatment other than dilution in PBS or after organic solvent extraction if high sensitivity is required.