Chimie des complexes de metaux de transition avec des hydrocarbures cyanes : III. Quelques observations sur la conformation et la reactivite de complexes dicyclopentadienyles du molybdene et du tungstene

A new class of cyclic telluronium salts has been prepared. All the salts are stable in solution in CHCl₃ or dimethylsulphoxide (DMSO). Conductivity measurements in DMSO and dimethylformamide (DMF) have shown that considerable ion pairing occurs in solution. Infrared, ¹H, ¹³C, ¹²⁵Te NMR, and mass spectra are reported and discussed.     

Separation and detection of oxidation products of fluorodeoxyglucose and glucose by high-performance liquid chromatography-electrospray ionisation mass spectrometry

2-Deoxy-2-[18F]fluoro-D-glucose ([18F] FDG), the most popular positron emitting radiopharmaceutical, may oxidise by autoradiolysis in aqueous solution. The aim of this work was to use LC-MS for determination of the oxidation products of fluorodeoxyglucose and glucose (Glc) obtained by oxidation with Fenton's reagent. Asahipak NH2P-50 polyamide silica column and acetonitrile-0.025% aqueous ammonium formate (80:20 (v/v)) eluent were utilised with an Agilent 1100 HPLC-MS instrument. Ten major oxidation products of FDG and Glc were separated and identified by mass spectrometry: 2-fluorogluconic acid, 2-fluoroglucuronic acid, 2-oxoerythronic acid, arabinose, arabonic acid, araburonic acid, erythrose, erythrulose, gluconic acid, and glucuronic acid. The most intensive electrospray ionisation signals were found in the negative ion spectra and were due to HCOO- adducts, the other acids being in their lactone forms.     

Atomic spectroscopy for detection in thermal analysis

An atomic absorption spectrophotometer is coupled to a conventional thermoanalytical quartz furnace as used for TG and DTG to detect the thermally evolved products. In this combined system, the dry aerosol (smoke) obtained by cooling the vapour evolved is transported from the furnace to the flame for metal-specific atomic absorption detection. The particular design of the furnace outlet promotes the formation of stable aerosols. Optimum experimental conditions were determined, using zinc chloride solution, by varying the specimen mass, the heating rate and the flow rate of the furnace gas at a linear temperature program. The absorbancevs. temperature curves obtained with this method for various zinc compounds are compared with the corresponding DTG curves. The applicability of the technique for studying heterogeneous reactions with carbon tetrachloride and hexane vapours is presented. The utilization of an atomic absorption spectrophotometer equipped with a quartz cuvette for detecting the thermal evolution of mercury vapours is described, as well as detection potentials by molecular absorption (for NO and NH₃) and light scattering (for smoke evolved from organic matter). The results obtained with the suggested methods may, in some respects, valuably complement the results achieved with DTG and with flame ionization detection.

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Zusammenfassung Ein Atomabsorptionsspektrometer wurde mit einem konventionellen thermoanalytischen Quarzofen gekoppelt um thermische Abspaltprodukte nachzuweisen. In diesem kombinierten System wird das durch Kühlung des entwickelten Dampfes erhaltene Aerosol (Rauch) vom Ofen in die Flamme für den metallspezifischen Atomabsorptionsnachweis übergeleitet. Die spezielle Ausbildung der Austrittsöffnung gewährleistet die Bildung eines stabilen Aerosols. Die optimalen Versuchsbedingungen wurden durch Zinkchloridlösungen bei Anderung der Probenmasse, der Aufheizgeschwindigkeit und der Strömungsgeschwindigkeit des Ofengases im linearen Temperaturprogramm ermittelt. Die mit dieser Methode für verschiedene Zinkverbindungen erhaltenen Absorptions—Temperatur-Kurven wurden mit den entsprechenden DTG-Kurven verglichen. Die Anwendbarkeit dieser Technik bei dem Studium heterogener Reaktionen mit Kohlenstofftetrachlorid und Hexandämpfen wird gezeigt. Der Einsatz eines mit einer Quarzküvette zum Nachweis der thermischen Entwicklung von Quecksilberdampf versehenen Atomabsorptionsspektrometers wird beschrieben, sowie die Nachweisgrenze durch molekulare Absorption (für NO und NH₃) und Lichtstreuung (für aus organischem Material entwickelten Rauch). Die bei den beschriebenen Methoden erhaltenen Ergebnisse können, in mancher Hinsicht, die durch DTG und Flammenionisationsnachweis erhaltenen Ergebnisse wertvoll ergänzen.

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- , , . (), , . . , . — , , -. . - , , , ( NO NH₃) ( , ). , , , - .

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Presented in part at the 24th Hungarian Conference on Analytical Sptecroscopy, Miskolc, June 15–18, 1981. Abstracts pp. 159–162.

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The authors wish to express their thanks to S. Gál for his assistance in the present application of the temperature programmer developed by him and his group, and for the valuable discussions on the subject. Thanks are also due to K. Tomor and J. Kmives who participated in the comparative thermoanalytical measurements and their analysis.     

Olefin polymerization in liquid sulfur dioxide initiated by m-chloroperbenzoic acid. I. Homopolymerization of styrene and α-methylstyrene

Homopolymerizations of styrene (Sty) and α-methylstyrene (AMS) in liquid sulfur dioxide were carried out in the temperature range from ?10°C to ?78°C, using m-chloroperbenzoic acid as initiator. It is shown, through the effect of initiator concentration, temperature, and times of reaction on the conversion and molecular weight of the polymers, that AMS is more reactive than Sty because it requires a smaller amount of initiator for the same conversion to be reached, although the molecular weight of the resulting polymer is lower. A linear relationship has been observed for Sty between the degree of polymerization and the initiator concentration. Within the experimental conditions employed, the presence of polysulfones has been discarded by elemental analysis. The polymerization reactions are considered to be cationic in mechanism.     

Bia-amperometric quantification of salbutamol in pharmaceutical products

This paper presents a simple, rapid and reproducible method of analysis of salbutamol in pharmaceutical products, utilizing batch injection analysis (BIA) associated with amperometric detection. A study of salbutamol oxidation demonstrated a strong dependence between electrode fouling and pH. All determinations were done utilizing a glassy carbon electrode in presence of 3.0 mol l⁻¹ NaOH. A large linear dynamic range from 8×10⁻⁷ to 2×10⁻⁴ mol l⁻¹ was obtained by using an injected volume of 100 μl with a detection limit of 2.5×10⁻⁷ mol l⁻¹. R.S.D. of 0.92% for 50 successive injections of 4×10⁻⁶ mol l⁻¹ of salbutamol and a sample throughput of 60 samples per hour were achieved. The method was applied for salbutamol quantification in syrups.     

Analysis of organic acids in wines by Fourier-transform infrared spectroscopy

Fourier-transform infrared (FTIR) spectroscopy has been a major point of development in many wine laboratories in recent years. It enables almost instant analysis of several properties of wine, usually with very good precision and accurate results. Nevertheless, validation procedures should not be forgotten and should be fully performed. Recovery experiments were performed by spiking wine samples with different amounts of organic acids (tartaric, malic, lactic, acetic and citric—the most prominent in wines). After FTIR analysis of the total acidity and of each organic acid concentration, recoveries were calculated. For total acidity recovery results were, in general, good and very close to 100% (64–111%). On the other hand, for individual organic acid concentrations, the recovery results were lower than 100% (11–73%) for all spiking additions. These results could be explained by spectroscopic interferences between the organic acids. Because they have similar infrared spectra, it is not easy to distinguish between them and, therefore, to achieve accurate calibration. When total acidity, with a different infrared spectrum from the other abundant compounds in the wine, was taken as a single property the recovery results were acceptable.