Evaluation of 40K in food by determining total potassium using neutron activation analysis

Summary Potassium is an extremely important major element to the human body. Potassium is made up of three isotopes with abundances of ³⁹K at 93.1%, ⁴⁰K at 0.0118% and ⁴¹K at 6.88%. It is also very well known that ⁴⁰K with its 1.3 ^. 10⁹ years half-life is a major naturally occurring isotope in the body and food. The usual way to determine total ⁴⁰K is to measure the single 1460.8 keV photon from beta-decay. However, this procedure requires a significant amount of sample and typical counting periods of at least a day in well-shielded germanium counting system. Another approach is to determine total potassium via neutron activation analysis using the well known ⁴¹K(n,g)⁴²K (T_1/2 = 12.8 h) reaction and then evaluate ⁴⁰K using the usual activity equation A = lN. In our laboratory we have effectively used epithermal neutron activation analysis and Compton suppression to determine potassium in air filters and other geological material. Upwards to 10-15 samples can be analyzed in one day using only gram quantities of material. In such way one can increase the output of determining ⁴⁰K by at least one order of magnitude. Results of a detailed investigation optimization of the methodology, quality control and detection limits will be presented for reference material and various food samples.     

Synthesis of Vinyl and β-Phthalimido Ketones

Vinyl ketones are prepared by reaction of an aldehyde with a vinyl Grignard reagent followed by a Swern oxidation. β-Phthalimido ketones are then obtained by 1,4-addition of phthalimide.     

Determination of cadmium in Arctic air filters by epithermal neutron activation analysis and Compton suppression

Arctic pollution is a problem of great concern, because its characteristics (transportation, assimilation into the environment, etc.) are complex and not fully understood. Detection of elemental constituents has been undertaken through the use of neutron activation analysis and Compton suppression (to lower the detection limits for radionuclides characteristic of mainly single gamma-ray emission) to discover possible pollutant sources. The goal of this project was to perform a feasibility study to determine the suitability of neutron activation analysis (NAA) to evaluate cadmium concentrations on air filters collected in the Arctic.     

Trace element content of medicinal plants from Algeria

Neutron activation analysis (INAA) has been applied to multielemental determination of eleven medicinal plants used to cure the urinary tract diseases observed in Algeria. These plants include Androgena Citratus, Ceratonia Siliquata, Punica Granatum, Glyryrrhiza Glabra, Lausaunia Alba, Fragaria Vesca, Arbutus Unedol, Hordeum Vulgaris, Papieteria Officinalis, Zea Mays L, and Davallia Seae. Concentrations of twenty elements Ba, Br, Ca, Cl, Co, Cu, Cr, Fe, I, Mn, Na, Mg, Rb, Sb, Se, Sc, Sr, Ti, V, and Zn have been determined by short, and long irradiation times with a thermal and epithermal flux of 1.4·10¹² n·cm⁻²·s⁻¹ and 1.4·10¹¹ n·cm⁻²·s⁻¹, respectively. These analyses were performed in conjunction with Compton suppression. In almost herbs studied the Co, Cr, Cu, Rb, Sb, Sc, Se and V are found to be present at trace levels, Br, Mn, and Zn at the minor level, and Ca, Cl, Fe, Mg and Na are generally at the major level. The accuracy of the measurements has been evaluated by analyzing NIST-botanical references materials.     

Mechanism of copper underpotential deposition at Pt(<Emphasis Type="Italic">hkl</Emphasis>)-electrodes: Quantum-chemical modelling

Mechanism of copper underpotential deposition at stepped faces of platinum single crystals Pt(hkl) is studied using cyclic voltammetry, scanning probe microscopy, and quantum-chemical modelling. It is shown that the first stage of UPD is one-dimensional decoration of the (100)- or (110)-orientated steps, then copper monolayer forms at (111)-terraces. The final stage is the secondary step decoration. Quantum-chemical modelling, with the using of long-distance potentials of the Cu-Pt and Cu-Cu pair interactions, allows estimating the energy of copper adsorption at different structure elements of the substrate (steps, kinks, terraces) and revealing the succession of the adatom monolayer formation; it also provides additional information for the identifying of the nature of voltametric peaks for different stages of the copper adsorption-desorption.