Differential heats of adsorption and adsorption isotherms of alcohols on silicalite

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2117–2120, September, 1989.     

Determination of mitomycin C in plasma, serum and urine by high-performance liquid chromatography with ultra-violet and electrochemical detection

The performance of a number of normal phase and reversed-phase systems, with ultraviolet detection at 360 nm, has been investigated with respect to their applicability to pharmacokinetic studies of mitomycin C (MMC). The reversed-phase system developed was also combined with a polarographic detector in order to compare the sensitivity and selectivity of ultraviolet and electrochemical detection. A simple isolation procedure, based on the adsorption of MMC on a non-ionogenic resin, has been developed. The developed assay is applied to a pharmacokinetic study from which some examples are given.     

Additional of functional vinylzinc reagents to nitrones: synthesis of (E)-N-allylhydroxylamines and their rearrangement into (E)-O-allylhydroxylamines

The vinylzinc reagents derived from hydrozirconation of alkynes and transmetallation add readily to nitrones to yield pure (E)-N-allylhydroxylamines; some of these rearrange into O-allylhydroxylamines.     

Reliable identification and quantification of trichothecenes and other mycotoxins by electron impact and chemical ionization-gas chromatography-mass spectrometry, using an ion-trap system in the multiple mass spectrometry mode. Candidate reference method for complex matrices

Highly toxic mycotoxins like the trichothecenes can be found as contaminants from the metabolism of fungi in food and food preparations. They can be identified and quantified with great accuracy by GC/MS-measurements. Reliable analytical methods are urgently needed because such mycotoxins are not only toxic substances occurring in nature but also are in the list of biological weapons (e.g. T2-toxin, HT-2-toxin) and have some potential for terroristic attacks. By using GC/MS in the EI- and NCI- or PCI-mode and MS(n)-measurements with a 30 m Rtx 5MS fused-silica capillary column it is possible to identify and quantify all relevant mycotoxins either as underivatized substances or as their TMS-derivatives in extracts from food, food preparations or beverages with very complex matrix-derived background. This method can also be used to determine free ricinine as a biological marker for ricine in terroristic attacks. So laborious and time-consuming steps of sample-preparation can often be diminished. The LOD is in the range of 10-50 pg and the LOQ with linear calibration curves is in the range of 50-5000 pg. The high specificity of these methods helps not only to detect the existence of intentional terroristic or natural food contamination but also to avoid faulty alarm with unnecessary panic in the public. Furthermore, these methods have a high potential in ameliorating the safety of basic food and food products.     

Optical rotary dispersion of nitrobenzene derivatives—IV : Absolute conformation of twisted nitrobenzen derivatives and its control through conformational transmission

The origin of Cotton effect shown by o-nitrobenzoyl esters is discussed. The Cotton effect observed for 1-(?)-methyl ester of 3-nitrophalic acid and 4-nitrohemimellitic acid (6 and 12), indicated that the favoured twisting direction of the nitrobenzene moiety is determined by the asymmetric menthyl group through the intervening carboxyl groups. This provides a new concept in conformational analysis of aromatic compounds. Extending the concept of conformational transmission to 2,2′-dinitrobipenhyl derivatives with known ab twisted nitrobenzene was related to the sign of the Cotton effect at 330 nm in accordance with the result of X-ray crystal analysis 1-(?)-menthyl 4-bromo-2-nitrobenzoate (1)     

Liquid-liquid extraction of cadmium(II) from aqueous thiocyanate solutions with liquid anion-exchangers

An investigation has been made on the system liquid anion-exchanger-Cd(II)-NCS⁻. The influence of the acidity and thiocyanate concentration of the aqueous phase on the extraction has been studied. Using various methods of analysis, it has been shown that the complex anion present in the organic extracts is Cd(NCS) ₄ ²⁻ . Details are given concerning the removal of traces of Zn(II) from Cd(II)-containing solutions, and the quantitative separation of Cd(II) from Cr(III).     

Adsorption and interaction of ethylene on RuO2(110) surfaces

Ethylene (C2H4) adsorbed on the stoichiometric and oxygen-rich RuO2(110) surfaces, exposing coordinatively unsaturated Ru-cus and O-cus atoms, is investigated by applying high-resolution electron energy-loss spectroscopy and thermal desorption spectroscopy in combination with isotope labeling experiments. On the stoichiometric RuO2(110) surface C2H4 adsorbs and desorbs molecularly. In contrast, on the oxygen-rich RuO2(110) surface ethylene adsorbs molecularly at 85 K and is completely oxidized through interaction with O-cus and O-bridge upon annealing to 500 K. The first couple of reactions are observed at 200 K taking place on Ru-cus: A change from pi- to sigma-bonding, formation of -C=O and -C-O groups, and dehydrogenation giving rise to H2O adsorbed at Ru-cus. Maximum reaction rate is reached for C2H4 chemisorbed at Ru-cus with O-cus neighbors on each side. A model for the first couple of reactions is sketched. For the final combustion, C2H4 reacts both with O-cus and O-bridge. Ethylene oxide is not detected under any circumstance.     

Preparation of a new carboranyl lactoside for the treatment of cancer by boron neutron capture therapy: synthesis and toxicity of fluoro carboranyl glycosides for in vivo 19F-NMR spectroscopy

The synthesis of new ortho-carboranyl lactosides 8, 17, 19 and glucosides 22 and 23 for the use in boron neutron capture therapy is reported. Carboranyl lactosides 17 and 19 as well as the glucosides 22 and 23 contain a fluorine atom to allow a noninvasive determination of these compounds in tumor cells by 19F-NMR spectroscopy. In cloning efficiency tests on human bronchial carcinoma cells the carboranyl lactosides 17 and 19 displayed almost no cytotoxicity. Thus, the considerably cytotoxic carboranyl alcohol 11 is detoxified when linked to a sugar moiety such as in carboranyl glucoside 22.     

Kinetics and Mechanism of the Photosensitized Oxidation of Furosemide*

Detection of O2(1δg) phosphorescence emission, γmax = 1270 nm, following laser excitation and steady-state competitive methods was employed to measure total rate constants, kT, for the reactions of the diuretic furosemide, 2-methylfurane and furfurylamine with singlet oxygen in several solvents. Correlation of kT values with solvent parameters and product identification shows that the reaction mechanism is strongly solvent dependent. In aliphatic alcohols, the dependence of kT on solvent parameters is similar to the one observed for triethylamine, suggesting a reaction mechanism involving partial charge transfer from the amino group to the singlet oxygen. In nonprotic solvents, the dependence of kT on solvent parameters resembles the behavior found for 2-methylfur-ane and furfurylamine, implying that mostly a 2 + 4 cy-cloaddition mechanism of singlet oxygen to furane ring of furosemide occurs in these solvents. These mechanistic differences are explained in terms of hydrogen-bonding interactions between the carboxylic group in the aromatic ring and the amino group of furosemide. Furthermore, direct generation of C2(1δg) by furosemide was detected. Quantum yields of 0.047 ± 0.003 and 0.078 ± 0.004 were determined in acetonitrile and benzene, respectively. This last result may be related, at least partially, to the photodynamic effects of this diuretic drug.