The determination of copper,lead and cadmium in an oyster homogenate by anodic stripping voltammetry

Oyster homogenate is digested with nitric and perchloric acids and analyzed by differential pulse anodic stripping voltammetry. The results are compared with the “probable concentrations” obtained from an intercalibration exercise.     

Synthesis and Structure of Ionic Liquids Containing the ­[Al(OC6H4CN)4]– Anion

The synthesis, structure, and physical properties of ionic liquids (IL) bearing the novel [Al(O–C₆H₄–CN)₄]^– ion as counterion to the commonly used [NR₄]⁺, [PR₄]⁺ and imidazolium ions are reported. Both the influence of the alkyl chain length as well as the functionalization with cyano groups is studied. These ILs are easily obtained by reaction of Ag[Al(O–C₆H₄–CN)₄] with the corresponding ammonium, phosphonium, and imidazolium halides. The stability towards electrophilic cations was investigated. All prepared salts have a window for the liquid phase of ca. 200 °C and are thermally stable up to 450 °C. The solid‐state structures reveal only weak cation ··· anion and anion ··· anion interactions in accord with the observed low melting points (glass transition points).     

Anodic stripping voltammetry with the florence mercury film electrode. determination of copper,lead and cadmium in sea water

The use of the rotating glassy carbon electrode mercury plated in situ for anodic stripping voltammetry has been investigated. The choice of electrode material is discussed. The effect of instrumental parameters on the stripping response for copper, lead and cadmium in sea water is studied, the results being in accordance with the theory of thin film electrodes. The variation in the observed sensitivity for the three metals in sea water is discussed in terms of complex-forming ligands. Lastly the performance of the film electrode is compared to that of the hanging mercury drop electrode.     

Direct determination of rate constants for coupling between aromatic radical anions and alkyl and benzyl radicals by laser-flash photolysis

Coupling rates between the radicals methyl, n-, sec-, tert-butyl and benzyl (R.) and the aromatic radical anions of 1,4-dicyanonaphthalene, 9,10-dicyanoanthracene and fluorenone (A-.) have been obtained using a new laser-flash photolysis method. The radicals R. and the radical anions A-. were generated by a photoinduced electron transfer reaction between the aromatic compound A and the alkyl or benzyl triphenylborate anion RB(Ph)3-. For the first time the rate constants of the coupling reaction between methyl and benzyl radicals with aromatic radical anions have been obtained. For all the measured coupling rate constants an average value of k1 = 1.9 x 10(9) M-1 s-1 was found with a relatively small variation in the coupling rates (0.8-2.9 x 10(9) M-1 s-1). The results demonstrate that the coupling rate k1 is insensitive to changes in the steric and electronic properties of the radicals and the structure and standard potentials of the aromatic radical anions.     

[B(O–C6H4–CN)4]– based Silver and Copper Coordination Polymers

A series of new coordination polymers bearing the [B(O–C₆H₄–CN)₄]^– anion was synthesized. Two new, one dimensional coordination frameworks of the type M[B(O–C₆H₄–CN)₄] (M = Ag, Cu) were obtained by salt metathesis. The reactivity towards organic Lewis‐bases was studied. The reaction with bidentate ligands yielded two dimensional networks with the general formula [M(L)][B(O–C₆H₄–CN)₄] {L = 2,2′‐bipyridine, 4,4′‐bipyridine, 1,2‐bis(pyridyl)ethane, 1,4‐diazabicyclo[2.2.2]octane}. The synthesis, properties and single crystal structure are reported.     

Visualizing the dose distribution and linear energy transfer by 1D and 2D ESR imaging: a potassium dithionate dosimeter irradiated with C6+ and N7+ ions

We report the application of one- and two-dimensional (1D and 2D) spectral-spatial electron spin resonance imaging (ESRI) for visualizing the dose distribution and linear energy transfer (LET) in a potassium dithionate, K2S2O6 (PDT), dosimeter irradiated with the heavy ions C(6+) and N(7+). The ESR spectrum in the irradiated PDT consists of a superposition of two isotropic signals assigned to two *SO3(-) radicals, R1 and R2, with no hyperfine splittings and slightly different g values. The 1D ESRI profiles clearly indicate the spatial penetration of the beams and the location of the sharp maximum dose, the "Bragg peak", detected for each beam. The depth penetrations are different: approximately 2.3 mm for C(6+) and approximately 1.8 mm for N(7+) beams, +/-0.1 mm; beyond these limits, no radicals were detected. 2D spectral-spatial ESRI images reflect both the dose distribution and the spatial dependence of the relative intensities of radicals R1 and R2, an effect that is assigned to the depth variation of the LET. This study has demonstrated that ESRI is a promising new method for dose and LET determination. Of particular interest are applications in the field of radiotherapy with heavy ions, because in this case the Bragg peak is pronounced and the dose can be focused at specific depths while the surrounding areas are protected.     

Simulation of the electronic and vibrational structure of hydrogenated amorphous silicon using cluster models

A set of simple models of hydrogenated amorphous silicon (a-Si:H) consisting of hypothetical silane molecules with diamond or similar lattices was studied by the semiempirical AM1 method. Densities of states and infrared spectra were calculated for the silane molecules and similar molecules with dangling bonds disorder, and with boron or phosphorus substitution to simulate doping. Some examples are presented, and a comparison is made with experimental properties of a-Si:H. It is proposed to use these models in a study of the Staebler–Wronski photodegradation of a-Si:H and other aspects of amorphous silicon technology. © John Wiley & Sons, Inc.