Quantifying Uncertainty in Quantitative TLC

JPC – Journal of Planar Chromatography – Modern TLC - The Eurachem/Citac Guide on measurement uncertainty establishes general rules for evaluating and expressing measure¬ment...     

Oxidation of AISI 304L stainless steel surface with atomic oxygen

Oxidation of stainless steel surface in oxygen atmosphere was investigated by Auger electron spectroscopy (AES) depth profiling. The samples made of AISI 304L stainless steel were exposed to highly non-equilibrium oxygen atmosphere at different temperatures between 300 and 800 K and for different periods between 5 and 600 s. The degree of dissociation of oxygen molecules was of the order of 10%. A thin oxide layer formed on the stainless steel surface consisted of the iron oxide. The thickness depended on the sample temperature. At room temperature it was 7 nm, and it remained the same up to 200 °C. With further increase of temperature, the thickness of the oxide layer increased and reached 40 nm at 450 °C. The thickness was independent of exposure time. The results were explained by two mechanisms of oxide growth. Up to 200 °C the oxidation was run by electro-migration, while at higher temperatures the thermal induced migration prevailed.     

Novel N-chlorinated derivatives of 2H-1-benzopyran-2-imines

A series of new N-chlorobenzopyran-2-imines were prepared in moderate to good yields, by reacting sodium hypochlorite in an acidic medium with benzopyran-2-imines obtained via the Knoevenagel condensation. Some of the N-chlorobenzopyran-2-imines obtained are potential antiproliferating agents.     

Cleaning of Porous Aluminium Titanate by Oxygen Plasma

The removal of organic contaminants from porous Al₂TiO₅ during treatment in oxygen plasma was studied by optical emission spectroscopy (OES). The samples of Al₂TiO₅ were immersed into water emulsion of mineral oil for 3 h to get soaked. Then, they were thoroughly cleaned in ultrasound to remove oil from the surface. Samples were later exposed to RF oxygen plasma at the pressure of 75 Pa. The plasma density was about 2 × 10¹⁶ m⁻³, the electron temperature was about 6 eV and the density of neutral oxygen atoms was about 2 × 10²¹ m⁻³. Optical emission spectra between 200 and 1,000 nm were measured continuously during plasma treatment. The CO peak resulting from oil oxidation reached a well-pronounced maximum between 100 and 150 s of plasma treatment. The maximum in CO corresponded well with a minimum in O peaks. Concentration of oil in the samples was estimated by energy dispersion X-ray analysis. Initially the samples showed high concentration of carbon (about 38 at.%), while after plasma treatment the carbon concentration decreased below the detection limit. The cleaning efficiency was explained by diffusion of oil towards the surface where it was removed by oxidation with oxygen radicals.     

Tunable carbon-carbon and carbon-sulfur cross-coupling of boronic acids with 3,4-dihydropyrimidine-2-thiones

Direct microwave-assisted Pd(0)-catalyzed/Cu(I)-mediated carbon-carbon cross-coupling of 3,4-dihydropyrimidine-2-thiones and boronic acids under Liebeskind-Srogl conditions leads to 2-aryl-1,4-dihydropyrimidines in moderate to high yield. In contrast, Cu(II)-mediated reaction of the same substrates leads to carbon-sulfur cross-coupling. [reaction: see text]     

Use of HPTLC for Quantitative Evaluation of Inulin in Food Products

JPC – Journal of Planar Chromatography – Modern TLC - HPTLC and HPLC—MS methods have been developed for quantitative determination of inulin in food products. Samples were applied...     

QASKI – the quality assurance system of the National Institute of Chemistry

 The quality assurance system (QASKI) developed and implemented in the National Institute of Chemistry is presented. It tries to eliminate the incompatibilies between the present methods of quality assurance used in research and development institutes such as good laboratory practice and accreditation. Since 1991, QASKI has been used for internal accreditation of laboratories located in the institute, regardless of the fact that some of them deal with routine analyses and others with research and development. Every laboratory that wishes to ensure the credibility of its research or routine work enters QASKI and at the same time chooses an external method of approval. All interested laboratories, study directors, principal investigators, internal auditing staff, heads of documentation, quality assurance unit staff, the Director of the institute and the Quality Management Board participate in the internal system.     

Synthesis and functionalization oftrans-2-(2′-aminocyclohexyloxy)-andtrans-2-(2′-azidocyclohexyloxy)acetic acid

Summary Synthesis of the hydrochloride oftrans-2-(2-aminocyclohexyloxy)acetic acid (4) fromtrans-2-(2-azidocyclohexyloxy)acetic acid (1) is described.4 was acylated at the amino group to give compounds5–8.1 was converted into acid chloride (9) and amides10–13.

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Synthese und Funktionalisierung dertrans-2-(2-Aminocyclohexyloxy)- undtrans-2-(2-Azidocyclohexyloxy)essigsäure

Zusammenfassung Die Synthese destrans-2-(2-Aminocyclohexyloxy)essigsäurehydrochlorids (4), ausgehend vontrans-2-(2-Azidocyclohexyloxy)essigsäure (1), wird beschrieben.4 wurde durch Acylierung der Aminogruppe in die Verbindungen5–8 übergeführt.1 wurde in das Säurechlorid9 und die Carbonsäureamide10–13 umgewandelt.

     

XPS study of the deposited Ti layer in a magnetron-type sputter ion pump

X-ray photoelectron spectroscopy (XPS) was used to study the surface chemical composition of the anode deposits in a miniature magnetron ion pump. The pump was mounted on an UHV system with the ultimate pressure of 1 × 10⁻⁹ mbar. A stable discharge was established in the nitrogen atmosphere with some traces of CO at about 10⁻⁷ mbar. The cathode was made of pure titanium. The sputtered titanium atoms deposited on the anode, where they reacted with gases to form a film of titanium compounds. The thickness of the deposited titanium layer on the anode was about 100 nm. The results from XPS investigations indicate that active gases such as O₂ and N₂ react with Ti forming TiO₂ and TiN. While carbon containing molecules just adsorb on the surface and do not form carbide. In the bulk of the deposited layer almost pure TiN was found with some traces of oxygen and carbon. The part of carbon was bonded to TiC, which can be caused by ion sputtering during the depth profiling.     

Length-Scale Dependence of Hydration Free Energy: Effect of Solute Charge

Size and curvature are important determinants of particle wettability, in addition to surface chemistry and texture. Hydration free energy of a nonpolar solute scales with volume for small solutes and with surface area for larger ones. If the solute acquires a surface charge, the scaling regimes can be affected, with size-dependence of the charge playing a critical role. For isolated particles grown at fixed surface charge density, the Born approximation gives scaling of hydration free energy with volume. We consider a distinctly different but practically important scenario, where the charged solute and surrounding counterions are dissolved together. For this process, our molecular simulations demonstrate the electrostatic contribution to the solvation free energy, calculated per unit area of the solute, to be virtually independent of solute size. We explain this behavior in terms of counterion shielding effect on the curvature-dependent solute energy in the dehydrated state, an effect closely balanced by the influence of dielectric screening in water. As a result, for moderate surface charge densities of the solute, the net electrostatic contribution is dominated by counterion solvation, and scales with solute surface area independently of the ionic strength in the solution.