Zur Kinetik der Umsetzung von Cystin mit o-Hydroxymercuribenzoesäure und Natronlauge

Zusammenfassung Es wird der zeitliche Verlauf der Zersetzung von Cystin und der Bildung von Cystein in Gegenwart von NaOH und o-Hydroxymercuribenzoesäure bei 50° und 60° untersucht und, soweit dies zulässig erscheint, eine reaktionskinetische Deutung der Zeit-Umsatzkurven vorgenommen. In den Reaktionsprodukten (bei 90°) wurde Thiocystein nachgewiesen.Mit 4 Abbildungen     

Elucidation of organic reaction mechanisms by direct observation of the intermediate by Raman Laser rapid spectrometry.

We have demonstrated the utility of Raman Laser rapid spectrometry in the detection of an unstable intermediate in an organic reaction by averaging a large number of spectra of the reaction mixture in the range of absorption of a characteristic Raman vibration mode.     

Application of gallium film electrode for elimination of copper interference in anodic stripping voltammetry of zinc

For elimination of copper interference in anodic stripping determinations of zinc at mercury and bismuth film electrodes gallium ions are usually added to the supporting electrolyte. In the presented studies novel ex situ formed gallium film electrode was applied for this purpose. The proposed electrode is less toxic than mercury one while the detection limit for zinc was lower than for bismuth film electrode following the same deposition time. The calibration graph for deposition time of 60 s was linear from 5 × 10⁻⁸ to 2 × 10⁻⁶ mol L⁻¹. The determinations of zinc were carried out from undeaerated solutions. The proposed procedure was applied to zinc determination in certified reference material and tap water sample.     

Adsorptive stripping voltammetric determination of cobalt in the presence of dimethylglyoxime and cetyltrimethylammonium bromide

A sensitive procedure for determination of micro-traces of Co(II) by adsorptive stripping voltammetry is proposed. The procedure exploits the enhancement of the cobalt peak obtained by use of the system Co(II)–dimethylglyoxime–piperazine-1,4-bis(2-ethanesulfonic acid)–cetyltrimethylammonium bromide. Using the optimized conditions, a detection limit (based on the 3 criterion) for Co(II) of 1.2×10^–11 mol L^–1 (0.7 ng L^–1) was achieved. The calibration plot for an accumulation time of 30 s was linear from 5×10^–11 to 4×10^–9 mol L^–1. The procedure was validated by analysis of certified reference materials and natural water samples.     

Influence of the grain morphology of V2O5 on its reduction-reoxidation behaviour

The influence of the grain morphology of V₂O₅ on its reduction-reoxidation behaviour has been investigated by means of thermoanalytical methods. X-ray analysis and electron microscopy. Well-developed V₂O₅ platelets exposing predominantly the (010) face exhibited a significantly different reduction profile than poorly defined agglomerates of microcrystalline V₂O₅. Intermediate phases detected during reduction were V₆O₁₃ and VO₂ (rutile). The corresponding reoxidation profiles were found to be only weakly dependent on the grain morphology of V₂O₃. Electron microscopy showed that the original grain morphology of the V₂O₅ samples was not influenced markedly by the reduction-reoxidation cycle.     

Alkylation and the Knoevenagel Condensation of Nitrobenzylic Sulfones and Nitriles.1

Nitrobenzylic sulfones and nitriles easily available via the vicarious nucleophilic substitution of hydrogen are readily alkylated in the catalytic two-phase systems, the latter enter also the Knoevenagel condensation with aldehydes.     

Efficient S-alkylation of cysteine in the presence of 1,1,3,3-tetramethylguanidine

The synthesis of S-alkylated cysteine derivatives was carried out successfully in the presence of 1,1,3,3-tetramethylguanidine. Alkylation proceeded in high yields on unprotected amino acids and peptides containing a sulfhydryl group.     

In search of elementary spin 0 particles

The Standard Model of strong and electroweak interactions uses point-like spin 1/2 particles as the building bricks of matter and point-like spin 1 particles as the force carriers. One of the most important questions to be answered by the present and future particle physics experiments is whether the elementary spin 0 particles exist, and if they do, what are their interactions with the spin 1/2 and spin 1 particles. Spin 0 particles have been searched extensively over the last decades. Several initial claims of their discoveries were finally disproved in the final experimental scrutiny process. The recent observation of the excess of events at the LHC in the final states involving a pair of vector bosons, or photons, is commonly interpreted as the discovery of the first elementary scalar particle, the Higgs boson. In this paper we recall examples of claims and subsequent disillusions in precedent searches spin 0 particles. We address the question if the LHC Higgs discovery can already be taken for granted, or, as it turned out important in the past, whether it requires a further experimental scrutiny before the existence of the first ever found elementary scalar particle is proven beyond any doubt. An example of the Double Drell–Yan process for which such a scrutiny is indispensable is discussed in some detail.     

New Protocol for Determination of Rifampicine by Adsorptive Stripping Voltammetry

For determinations of organic compounds by adsorptive stripping voltammetry till now the same material of the electrode has been used for the accumulation and stripping steps. This paper describes a new protocol for extending the range of organic compounds, which can be determined by adsorptive stripping voltammetry. In the proposed procedure the accumulation step was performed on the electrode modified by a lead film, which assures adsorption of the studied species on the modified electrode and then the stripping step of the accumulated substance was performed on the support of the lead film electrode. As an example rifampicine was accumulated by adsorption at the lead film electrode while in the stripping step lead film and then the accumulated rifampicine were oxidized at a glassy carbon electrode. Using an acetate buffer as a supporting electrolyte a calibration graph for rifampicine in the range from 2.5×10^?10 to 1×10^?8 mol L^?1 was obtained. The detection limit for rifampicine following 60 s accumulation time was equal to 9×10^?11 mol L^?1. The obtained detection limit was comparable or lower than reported previously for other stripping voltammetric procedures. The proposed procedure was applied to rifampicine determination in pharmaceutical preparation.