Beseitigung des Matrixeffekts bei der Analyse von Edelmetallspuren mit induktiv gekoppeltem Plasma

Summary Spectral interferences associated with the determination of trace contents of Au, Ag, Pt and Pd in samples with complex matrices (hydrometallurgical solutions, metallurgical products and ore processing products) were investigated. It was found that it is necessary to separate Au, Pt and Pd from the matrix elements. The results obtained with various methods for separation and pre-concentration of these elements showed that in the case of hydrometallurgical solutions adsorption on activated carbon satisfies the requirements of analytical control. For the determination of these elements in ore processing products it is necessary to use additional extraction for their preconcentration. The most suitable organic solution found for the extraction of Au, Pt and Pd and their determination with ICP is isoamyl alcohol.     

Reactions of Alkenediazonium Salts. Part 2. Methanolysis of 2,2(2′,2″-biphenylylene)ethene-1-diazonium hexachloroantimonate. A rearrangement to 9-methoxyphenanthrene

The title compound ( 1 ) reacts with excess methanol forming a rearranged product, 9-methoxyphenanthrene ( 2 ). 9-(Methoxymethylidene)fluorene ( 4 ) does not rearrange to give 2 under the same conditions. In deuterated methanol no labelled product is obtained, showing that the possible mechanism involves either the formation of a primary vinyl cation 5 rearranging to an aryl cation 6 or the formation of a β-alkoxycarbene ( 12 ), which rearranges to an arene. The results obtained are compared with previously reported reactions, which were postulated to proceed via a 2,2(2′,2″-biphenylylene)ethene-1-diazonium ion ( 23 ).     

Untersuchungen zur gleichzeitigen Bestimmung von Molybd?n und Wolfram in Proben mit schwierigen Matrices mit induktiv gekoppeltem Plasma

Summary Inaccurate values are often obtained in the determination of molybdenum and tungsten in difficult complex matrices — ores, processing and metallurgical products. The main reason for this effect is due to spectral interferences. Background equivalent concentrations caused by changes of background nearby the measured spectral line are calculated for the established interferent matrix elements. It is possible with the applied sample treatment to perform successful analyses of samples with very variable matrix composition.     

Lewis acid-promoted Kharasch-Curran additions: a competition kinetics study of bromine atom transfer addition of N-alpha-bromoacetyl-oxazolidinone to 1-hexene

Lewis acids can efficiently promote free radical atom transfer reactions of an oxazolidinone imide substrate, 1, derived from alpha-bromo acetic acid. Thus, 1 undergoes a radical chain addition to 1-hexene giving the atom transfer addition compound, 6, in the presence of scandium or ytterbium triflate in 1,2-dichloroethane or a cosolvent mixture of 1/9 THF/dichloromethane. In 1,2-dichloroethane the solution is heterogeneous, while the cosolvent mixture gives a homogeneous solution, even at temperatures of -78 degrees C. Competition experiments were carried out in both solvent systems with added carbon tetrachloride to study how Lewis acid affected the product distribution. In the presence of carbon tetrachloride, chloride 7 is formed in addition to 6 and the ratio of these two products depends on the amount of Lewis acid present. In the presence of ytterbium triflate, in the cosolvent system, the reaction rate of bromine atom transfer was enhanced up to 400-fold compared to the reaction without added Lewis acid. Significant rate enhancements were also obtained in the solvent 1,2-dichloroethane, although the analysis of the system is complicated by the heterogeneous nature of the medium. Computation of C-Br bond dissociation energies (BDE) of the complexed and uncomplexed oxazolidinone bromide suggest that complexation lowers the BDE due to the effect of the strong electron-withdrawing group on the C-Br bond dipole.     

Fractional Dynamical Systems: Recent Trends in Theory and Applications

In this EPJ Special Topics issue selected contributions on some recent developments in the theory and applications of fractional dynamical systems are presented. Results on topics involving fundamental theory, qualitative theory, iterative methods and numerous applications of fractional-order equations are reported.     

Applicability of MiniPal 4 compact EDXRF spectrometer for soil and sediment analysis

Optimum measurement parameters for analysis of soil and sediment samples with the compact MiniPal 4 (MP4)EDXRF spectrometer (PANalytical, Almelo, The Netherlands) were presented. The following elements were considered: K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As and Pb. Since the elements from low Z to medium Z region were covered, three measurement conditions (sequences) were defined. The following parameters were selected for measurement of the elements K, Ti, and V: voltage = 12 kV; current = 750 µA; filter material: Al_thin. Cr, Mn and Fe were measured at 20 kV; 300 µA with Al filter while for measurements of Ni, Cu, Zn, As, Pb, Rb, and Sr an Ag filter was selected and tube voltage and current were 30 kV and 300 µA. Each sequence was measured for 200 s and measurements were done in the air. MP4 spectrometer was characterized with acceptable precision, long‐term stability and satisfactory minimum detection limit for the analyses of soil and sediment materials. For the elements K, Mn, Fe, and Ti the precision of the analysis was better than 0.5% and for all the other elements better than 5%. Detection limits for sediment samples were 20 ppm for K, 6.1 ppm for Ti, 5.2 for Mn, 4 ppm for Fe, 4.2 ppm for As and less than 2 ppm for all the other elements. These values were significantly lower compared to typical concentrations of the same elements found in unpolluted soil and sediments. Copyright © 2008 John Wiley & Sons, Ltd.     

Stability analysis of differential equations with maximum

In this paper, we investigate stability of the zero solution of differential equations with maximum by using Lyapunov functions and Razumikhin techniques. Sufficient conditions for stability, uniform stability and asymptotic stability of the zero solution of such equations are found.     

Amino-β-lactams in Ugi reaction: An efficient method for preparation of functionalized peptidomimetics

A synthetic strategy for the Ugi reaction on amino-β-lactam synthon 1 was developed. The Ugi reaction products 5 were obtained in satisfactory yields (47–78%) and generally, low diastereoselectivity (up to 72:28 dr). In case of Ugi products 5 derived from cyclohexylcarbaldehyde and amino-β-lactam 1, the reaction yields were lower (38–61%) but the products were obtained in high diastereoselectivity (>95:5).     

Total lipids of the intramuscular tissue of fallow deer

In this study non-isothermal non-oxidative and oxidative TG analysis was applied as a method for determining the thermal stability of the total lipids extracted from raw and maturing intramuscular tissue of fallow deer (Cervus Dama Dama L.). The total lipids were extracted from intramuscular tissue, according to the Folch method and stored for nine months at +4 and −18°C. The changes in the thermal stability of the total lipids during non-oxidative and oxidative TG analysis were correlated with the lipid composition, i.e. fatty acid composition. The Flynn-Wall method was used to determine the values of the activation energy of thermal degradation of the total lipids in a defined mass loss range.