New In-situ Sampling and Analysis of the Production of CeO<Subscript>2</Subscript> Powders from Liquid Precursors using a Novel Wet Collection System in a rf Inductively Coupled Thermal Plasma Reactor. Part 1: Reactor System and Sampling Probe

A new reactor and a novel in-situ sampling technique were developed for the study of the synthesis of CeO₂ powders produced from dissolved cerium nitrate salts. The conical reactor minimized particle recirculation and provided a highly symmetrical and undisturbed plasma flow suitable for the analysis of the phenomena affecting the formation of CeO₂ powders. Both a calorimetric study of the reactor and a thermodynamic analysis of CeO₂ formation were conducted. The sampling probe is described and near-isokinetic sampling was achieved. The sampled particles were collected using a miniature wet collection system, i.e. a mist atomizer and a custom-made spray chamber. A numerical simulation of the velocity and temperature fields of the plasma gas in the reactor was done using Fluent. A comprehensive droplet-to-particle formation mechanism presented elsewhere is revisited and expanded based on calorimetry, thermodynamics of CeO₂ formation, numerical simulations and collected particles. No traces of other oxidation states other than CeO₂ were found.     

Preconcentration of Cadmium and Zinc on a Chelating Sorbent and Their Determination by Flame Atomic Absorption Spectrometry

A method is developed for cadmium and zinc preconcentration on a minicolumn packed with a new chelating polymer sorbent. The effects of the test solution pH and volume, the sample matrix composition, the eluent volume, and the sample and eluent flow rates are studied. Zinc and cadmium in the eluate are determined by flame atomic absorption spectrometry. Under optimal conditions, the determined ion recovery is more than 95%. The detection limits (3σ, n = 20) are found to be 15.0 (Cd) and 17.2 (Zn) ng/mL. The developed method is employed for cadmium and zinc determination in samples of seawater and water obtained after oil pumping.     

Flow-injection analysis with a small cylindrical wire type electrode

An amperometric detector with a small thin mercury film electrode is described. The device demonstrates advantageous operational characteristics such as small dispersion (D<2) and “memory effect” (me<0.6%), extensive maximum sample frequency (msf −200 samples/h), and high sensitivity. It has been proven useful in flow-injection analysis at a constant potential under hydrodynamic conditions.     

Case Study: Doping Substances in Equestrian Food Supplements

In the course of investigations on equestrian supplemental products for the presence of doping substances, two products were found to contain forbidden substances. As reported earlier a plant extract (Mexican cactus extract) named “Energy 5” contained the anabolic androgenic steroids (AAS) stanozolol, 17β-hydroxy-17α-methyl-5α-androstane-3β-ol (3β,5α-THMT) as well as mestanolone not declared on the label. In the present study, a product called “Super Kalm Paste” was tested. Analysis by gas chromatography - mass spectrometry (GC-MS) revealed that the preparation contained the class I anti-arrhythmics quinine (trade names Kinidin^TM, Durules) and cinchonine. The samples were prepared according to a sample preparation procedure established for anabolic steroids in nutritional supplements for humans. The sample treatment comprised the extraction and purification of the analytes as well as the chemical conversion with N-methyl-N-trimethylsilyl-trifluoracetamide (MSTFA) to yield the trimethylsilyl (TMS)-derivatives. To verify whether the administration of such products could lead to positive doping tests, a pilot excretion study on “Energy 5” was conducted with two geldings, and urine samples were collected. Gas chromatography - high resolution mass spectrometry (GC-HRMS) after solid phase extraction and mixed derivatisation has demonstrated the presence of the stanozolol metabolite 16β-hydroxy-stanozolol in urine samples after “Energy 5” application.     

Thermal analysis and X-ray studies of chiral ferroelectric liquid crystalline materials and their binary mixtures

Summary Thermal properties of a homologous series of ferroelectric liquid crystals S-(-)-[4-(2-n-alkoxy-propionyloxy)]biphenyl-4'-[n-alkoxy-(3,5-dimethyl)]benzoate have been investigated by polarizing optical microscopy and differential scanning calorimetry. The mesophases were identified and confirmed by X-ray too. Three binary mixtures were prepared from the individual homologues. In one of the mixtures (Mix1), the ferroelectric SmC* phase has broadened and became enantiotropic. This mesophase remained monotropic in the other two mixtures (Mix2, Mix3). The chiral nematic N* phase did not appear in Mix1, but remained monotropic for the other two mixtures. Two molecular parameters, the layer spacing and the average intermolecular distance have been calculated from the X-ray results for the homologues and their mixtures. An intercalated tail-to-tail packing of molecules was found both in the single compounds and their mixtures resulting in the layer spacing about half of the molecular length of the single compounds.     

Chiral Compounds Synthesized by Biocatalytic Reductions [New Synthetic Methods (51)]

It has been known for many decades that chiral compounds can be obtained by stereospecific biocatalytic reduction. Further significant methodological developments in this field have, however, only been made during the past ten years; they include the application of previously unused microorganisms and electron donors, the discovery of additional substrates for the known reductases, the development of methods for regenerating reduced pyridine nucleotides, and the discovery of new reductases which were sought for specific preparative purposes. Many chiral compounds can now be synthesized by microbial hydrogenation using H₂ and hydrogenase-containing microorganisms as well as by electromicrobial or electroenzymatic reduction. In the two latter methods, anaerobic or aerobic organisms are supplied with electrons from electrochemically reduced, artificial mediators, e.g., methyl viologen. Reductases that do not require pyridine nucleotides and can accept electrons directly from reduced viologens are especially useful. Two examples of this type of enzyme are described which are of preparative interest. Many cells contain methyl viologen-dependent NAD(P) reductases, a large number of which have still not been characterized. A productivity number is proposed which allows different methods of bioconversion with microorganisms to be compared. The productivity numbers of compounds synthesized by the methods described in this review are often 10- to 100-fold higher than those of substances obtained by conventional techniques.     

Analytical Detectors Based on Microplasma Spectrometry

Miniaturizing all dimensions of apparatus, such as electronics and computers, is the current trend followed by scientists in various fields. The idea of Lab-on-a-Chip has significantly expanded and found its broad applications in analytical chemistry. Microplasmas can act as a sample excitation source and are the miniaturized versions of full-sized plasmas. These can be created in various forms, such as direct current, microwave induced, capacitively coupled and inductively coupled plasmas. Scaling down the size would reduce the amount of gases, liquids and consumables required, as well as the sample analysis time, which in turn would decrease the operating costs. Therefore, several research groups are involved in the development of microplasmas for utilisation in analytical instruments.