In memoriam

Prof. Dr. GüNTER SAUERBREY, 1933–2003 Günter Sauerbrey died on 15 May, 2003, a few days after his 70^th birthday. For 24 years he was responsible for the Laboratory of Medical Techniques and Dosimetry of the Physikalisch-Technische Bundesanstalt, Berlin and he also taught at Universities. His important invention was the use of a quartz oscillator as a mass sensor, the quartz crystal microbalance (QCM), which he developed in his research for his doctoral thesis at the Technical University at Berlin. He described that method in two often cited papers: Phys. Verhandl., 1957. 8: p. 193 and Z. Physik, 1959. 155: p. 206–222. With the QCM, Sauerbrey introduced a new class of mass measuring devices: inertial balances. The Sauerbrey equations are the basis of all vibrational weighing systems. His experiments on QCM allowed the extension of Einstein’s equivalence principle from uniform fields to time-dependent fields. Further work was on radiometry, thermometry, medical measuring techniques, high-temperature and vacuum physics. Günter Sauerbrey participated at several Conferences on Vacuum Microbalance Techniques and discussed at these events, in particular, applications of the QCM. Requiescat in pace. Erich Robens, Vasile Mecea     

In memoriam

Prof. Ing. Zdeněk Šolc, CSc (21 September 1931–30 September 2006) Prof. Zdeněk Šolc was born in 1931. After finishing his university studies, he joined the University of Pardubice where he remained for more than 50 years. He started to work at the Department of Physical Chemistry. His main fields of interest were: preparation of monocrystals, crystallization from solutions, measuring of physical and chemical properties of solutions. In the 1960's he turned to inorganic technology, studying inoranic pigments and he moved to the Department of Inorganic Technology. In this vast area of science, he achieved his greatest successes, and pigments became his ever-lasting passion up to the end of his life. The research in the field of crystallisation was oriented to development of liquid crystals for use in temperature indication, and materials for integrated circuits; besides that a school of inorganic pigments was formed (M. Trojan, Z. Šolc, D. Brandová) whose main orientation is mixed oxide materials for use in ceramics and enamels. A predominant part of the mentioned research activities was pursued at KAnT in 1990–1996, when the Department was headed by Professor Ing. Zdeněk Šolc. Most of Prof. ŠolcŠs projects were focused on the reactivity of inorganic pigments and powder materials, research of their high-temperature syntheses and rating of their physical and chemical properties. He applied mainly simultaneous thermal analytical techniques: thermogravimetry, differential thermal analysis using dynamic measuring conditions and quasi-isothermal and quasi-isobaric ones, moreover emanation thermal analysis and thermal conductivity measurements. Prof. Zdeněk Šolc was a creative scientist. He published more than 50 scientific papers in international journals and wrote 10 textbooks. He was the author of almost 100 lectures of conferences held in the Czech Republic and foreign countries. He had a silent but a very kind personality and he will be missed very much both by the local and the international communities. Requiescat in pace     

Pulsed dual electrospray ionization for In/In reactions

A pulsed dual electrospray ionization source has been developed to generate positive and negative ions for subsequent ion/ion reaction experiments. The two sprayers, typically a nano-electrospray emitter for analytes and an electrospray emitter for reagents, are positioned in a parallel fashion close to the sampling orifice of a triple quadrupole/linear ion trap tandem mass spectrometer (Sciex Q TRAP). The potentials applied to each sprayer are alternately pulsed so that ions of opposite polarity are generated separately in time. Ion/ion reactions take place after ions of each polarity are sequentially injected into a high-pressure linear ion trap, where axial trapping is effected by applying an auxiliary radio frequency voltage to the end lenses. The pulsed dual electrospray source allows optimization of each sprayer and can be readily coupled to any spray interface with no need for instrument modifications, provided the potentials required to transmit the ion polarity of interest can be alternated in synchrony with the emitter potentials. Ion/ion reaction examples such as charge reduction of multiply charged protein ions, charge inversion of peptides ions, and protein-protein complex formation are given to illustrate capabilities of the pulsed dual electrospray source in the study of gas-phase ion/ion chemistry.     

In Process Citation

A simple method is described for the microdetermination of deuterium in organic compounds. It involves a flash combustion of the weighed sample in a hot empty chamber at 950-1050 degrees and swept by oxygen at 60 ml/min. Together with this combustion in the gaseous phase, an oxidation of the primary combustion gases on cupric oxide at 850 degrees is necessary. Oxidation products containing halogens and sulphur are retained on silvered alumina at 750-800 degrees . Combustion water containing deuterium oxide and hydroxide is frozen out from the combustion gases in a special trap with two five-way stop-cocks which make possible the simultaneous flow of oxygen and hydrogen; the latter is used as a carrier-gas in the apparatus from the trap downwards. The frozen water is then vaporized by heating in a hydrogen flow of 30 ml/min and reduced on magnesium at 600 degrees . Deuterium is obtained as deuterium hydride in hydrogen; it is measured versus pure hydrogen, with a thermal conductivity detector. A Determination within a series can be completed in 15 min. The precision of the results is that obtained in classical organic microanalysts.     

In Process Citation

The formation of a metal-complex of copper(II) with vancomycin, an antibiotic active towards Gram-positive bacteria, has been proved by spectrophotometric, polarographic and potentiometric methods. In particular, the half-wave reduction potentials and voltamperograms indicate the stoichiometry of the addition compound and the equilibrium constant. This complex has been used for determination of vancomycin by a continuous flow method with copper(II) and amperometric detection in a polarographic cell of thin-layer type.     

In Process Citation

A micromethod for determination of nitrite is based on a reaction with o-tolidine, forming a yellow-orange product suitable for spectrophotometry. The sensitivity is 0.05 mug of nitrite ml . The method is suitable for analysis of potable and mineral waters, and has a mean relative error of 1%.     

In Process Citation

The variation in heat capacity and the thermal shifts which accompany a thermometric determination make the thermogram, even in the case of a very rapid and irreversible reaction, hyperbolic instead of formed of straight segments. These departures from linearity, which are inconvenient in the interpretation and exploitation of the thermograms, can be calculated as a function of the degree of titration. The relation obtained introduces a parameter which the authors call the apparent change of capacity at the equivalence point, and which takes into account the two causes of deviation from linearity. This relationship is confirmed experimentally.     

In Process Citation

Several flavonols of therapeutic interest on account of their vascular properties have been studied. They were all derived from the o-diphenol quercetol. Their electrochemical oxidation at a rotating solid electrode has been examined, and the choice of solvent and pH is discussed. Results obtained by d.c. and pulse polarography are presented. A relation between their structure and electrochemical behaviour has been established. Application to drug analysis is proposed, giving identification, determination and purity assay simultaneously. There is a linear response over the range 5 x 10(-6)-10(-4)M, a sufficient range for analysis of pharmaceuticals.     

In Process Citation

A rapid simple method is described for the determination of carbon in organic compounds. The technique is based on a flash-combustion of the weighed sample (1-3 mg) in a hot empty combustion chamber at 950-1050 degrees and swept by a stream of oxygen at a rate of 80-100 ml min . Together with this flash and dynamic combustion in oxygen, a cupric oxide filling at 850 degrees is necessary. Halogens and sulphur oxidation products are retained by means of a silvered alumina filling at 750-800 degrees . Water and acidic oxides of nitrogen are absorbed at room temperature by means of magnesium perchlorate and manganese dioxide respectively. Carbon dioxide is absorbed in the cathodic compartment of an automatic coulometer and generates H(+) ions which are neutralized by OH(-) obtained by electrolysis. This method makes possible the determination of carbon in compounds containing halogens (including fluorine), phosphorus and metals. However, some metal compounds with polynuclear rings in their molecules give low results and require the addition of an oxidant to the sample in the boat for complete combustion. Vanadium pentoxide seems to be the best oxidant in the present working conditions. Solid samples are weighed and analysed in platinum or porcelain boats; liquid samples are weighed in Pyrex capillaries which are laid in platinum boats and covered with a small piece of platinum gauze. When normal liquid samples are analysed, one tip of the capillary is broken before its introduction into the combustion tube but in the case of volatile liquid samples the sealed capillary is introduced into the combustion chamber, where it explodes. The precision obtained is better than that of the classical methods.     

In Process Citation

An HPLC method for the identification and determination of BHT (3,5-di-tert.butyl-4-hydroxytoluene) and the by-products obtained from it by β-ray or oxidative treatment is described. The chemical structure of the by-products is established by mass spectrometry. The irradiation leads to the dimeric and trimeric forms of the antioxidant and the oxidation to a cyclohexa-2,5-dien-1-one with substitution of a hydroxy and a methanol or aldehyde group at position 4.     

In Process Citation

Oxidation of 6-methoxyquinoline with vanadate shows the possibility of initial complex formation between the dioxovanadium(V) ion VO⁺₂ and the ethereal oxygen atom. The opening of the homocycle yields mainly 2-pyridone-3-carboxylic acid. In the case of quinine or mefloquine, the VO⁺₂ ion preferentially forms a pentagonal chelate with the secondary alcohol function. Oxidation of this complex initially produces quinoline-4-carboxylic acids. The acid that results from mefloquine is stable in the reaction solution and this property allows a reproducible consumption of reagent and a quantitative determination of this new antimalarial drug.     

In Process Citation

In the study of complex formation in aqueous solution by means of pH measurements, it is very useful to know the free ion concentrations in order to find each species composition and then calculate approximate values of their stability constants. From the pH determination alone, the unmeasured free ion concentrations can be calculated by a method in which a minimum number of integration and derivation steps are required. This process, called CILS, has been entirely computerized, and its conditions of application are illustrated with a simulated example.     

In Process Citation

On a effectué une étude spectrophotométrique dans l'ultra-violet, des complexes formés par l'acide anthranildiacétique (ANDA) avec le scandium(III), l'yttrium(III) et le lanthane(III) qui a permis de doser ces éléments. On a établi que ces complexes possèdent la composition Me-ANDA = 1:1 et on a calculé leurs constantes d'instabilité apparente : K = 1,5 . 10(-6) pour le complexe Se-ANDA, K = 3,4 . 10(-6) pour Y-ANDA et K = 2,9 . 10(-6) pour La-ANDA. A spectrophotometric study of the complexes formed between anthranil-N,N-diacetic acid, ANDA, and scandium, yttrium and lanthanum, has led to the development of methods for the determination of these elements. The instability constants for the complexes, in which the Me: AND A ratio is 1:1, were found to be 1.5 x 10(-6), 3.4 x 10(-6) and 2.9 x 10(-6) for Sc-ANDA, Y-ANDA and La-ANDA respectively.     

In Process Citation

The reversibility of the determination reaction is the most frequent cause of deviations from linearity of thermometric titration curves. Because of this, determination of the equivalence point by the tangent method is associated with a systematic error. The authors propose a relationship which connects this error quantitatively with the equilibrium constant. The relation, verified experimentally, is deduced from a mathematical study of the thermograms and could probably be generalized to apply to other linear methods of determination.     

In Process Citation

Carbonate as impurity often interferes in acid-base titrations. To take into account the liquid-gas equilibrium [H(2)CO(3) right harpoon over left harpoon CO(2(g)) H(2)O)] a new method is proposed: neutratizations are performed in a closed system with a known volume of gaseous phase. The corresponding equations, processed by multiparametric refinement, are successfully applied in the extreme case, viz. neutralization of a strong acid by sodium carbonate solution.     

In Process Citation

The sample (up to 5 mg) is destroyed by using a wet process in a glass flask of the Kjeldahl type. Aluminium cobalt, tin and iron are determined spectrophotometrically. The following reactions are used: complexation of aluminium by Alizarin Red S and calcium cobalt(II) by tiron tin(IV) by phenylfluorone, iron(III) by tiron.     

In Process Citation

Weak bases can be titrated potentiometrically or conductimetrically in phenol-water mixture (90/10 w/w). A spectrophotometric study in presence of 2,4-dinitrophenol is used to establish a classification of organic bases that is superposable on that found for other solvents; measurement of the dielectric constant confirms that the solvent is a hemihydrate. The methods of titration and range of application to many organic bases of pharmaceutical interest are described.     

In Process Citation

Carboxylic acids react with hydroxylamine hydrochloride in the presence of dicyclohexylcarbodi-imide to give the corresponding hydroxamic acid which is developed with iron(III), thus allowing colorimetric determinations on the tenths of a milligram scale. Esters do not react, and acetic acid can be determined in butyl acetate at a concentration of about 0.1%.     

In Process Citation

After a statement of the main requirements for an analytical system to be suitable for use in industry, a detailed examination is made of the response of each part of an activation installation (choice of neutron source and detector, transfer system for standards and samples, data handling) to these requirements. Several applications already established in industry are mentioned (determination of oxygen, nitrogen, fluorine, silicon). Some continuous analyses are also mentioned.     

In Process Citation

In the presence of an alkylamine, a guanidine or a quaternary ammonium hydroxide, liberated from their salts by the action of silver oxide, nitromethane reacts with 1,3,5-trinitrobenzene, yielding a red compound which allows the colorimetric determination of the nitrogenous base.