Investigation of the quantitative properties of the quadrupole orthogonal acceleration time-of-flight mass spectrometer with electrospray ionisation using 3,4-methylenedioxymethamphetamine

This paper describes the investigation of the potential of a quadrupole orthogonal acceleration time-of-flight mass spectrometer (Q-TOF) equipped with an atmospheric pressure ionisation interface for quantitative measurements of small molecules separated by reversed phase liquid chromatography. To this end, the detection limits and linear dynamic range in particular were studied in an LC/MS/MS experiment using 3,4-methylenedioxymethamphetamine standards and 3,4-methylenedioxyethylamphetamine for internal standardisation. In a second phase, the experiment was repeated with real biological extracts (whole blood, serum, and vitreous humour). A calibration for 3,4-methylenedioxymethamphetamine and its metabolite 3,4-methylenedioxyamphetamine was prepared in each of these matrices again using 3,4-methylenedioxyethylamphetamine as internal standard. The resulting quantitative data were compared with those obtained by liquid chromatography with fluorescence detection for the same extracts. The Q-TOF results revealed excellent sensitivity and a linear dynamic range of nearly four decades (2-10 000 pg on-column, r(2) = 0.9998, 1/x weighting). Furthermore, all the calibration curves prepared in biological material were superimposable, LC/MS/MS and LC-fluorescence, and the quantitative results for actual samples compared very favourably. It was concluded that the Q-TOF achieves a linear dynamic range for quantitative LC/MS/MS work exceeding that of fluorescence detection and at much better absolute sensitivity. Copyright 1999 John Wiley & Sons, Ltd.     

The photochromic properties of indoline spirooxazine-thermoplastic polymer systems obtained by supercritical fluid impregnation

The impregnation of thermoplastic polymers (polyethylene, polypropylene, polymethyl methacrylate, and polycarbonate) with photochromic compounds from the class of indoline spirooxazines in supercritical carbon dioxide (SC-CO₂) was studied. The concentration of the photochrome and the kinetics of decolorization of its colored form depended strongly on the type of the polymer matrix and the structure of spirooxazine. The introduction of 1,3′,3′-trimethylspiro(indoline-2′,3-3H-anthraceno[2,1-b][1,4]oxazine) (SAO) into polycarbonate caused anomalous stabilization (the prolonged conservation of the excited colored form of SAO in the polymer matrix). In contrast to other photochrome-polymer pairs, after supercritical impregnation into polycarbonate, at least 10% of all SAO molecules were in the colored form, which was highly stable and did not decolorize after 150 days; the rest of the impregnated SAO molecules were localized in the matrix as individual molecules, partially colorized after matrix relaxation, or nanocrystals of characteristic sizes ∼10–20 nm. The mechanisms of the anomalous stabilization of the colored SAO form in the polycarbonate matrix are discussed. Original Russian Text ? N.N. Glagolev, A.B. Solov’eva, A.V. Kotova, V.T. Shashkova, B.I. Zapadinskii, N.L. Zaichenko, L.S. Kol’tsova, A.I. Shienok, P.S. Timashev, V.N. Bagratashvili, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 5, pp. 985–992.     

Effect of the composition and structural and size characteristics of composites based on stabilized zirconia and transition metal (Cu,Co, Ni) oxides on their catalytic properties in methane oxidation reactions

The effects of transition metal (Cu, Co, Ni) oxides and platinum-group metals (Pt, Pd, Rh) in composites based on Y(Sc)-stabilized zirconia on their catalytic properties (activity, selectivity, sulfur resistance) and service life characteristics (thermal stability, performance stability) in methane oxidation reactions have been investigated. The high activity of the composites (75–99% methane conversion at 600–800°C) correlates with the amount and mobility of surface oxygen in these materials. The promoting effect of the platinum-group metals depends on the composition of the reaction medium (on whether it corresponds to the partial or total methane oxidation and on whether it contains sulfur dioxide).     

Effect of preparation conditions on the pore structure of tricalcium phosphate and on the kinetics of its reaction with the lead ion in solution

The kinetics of the reaction of differently prepared tricalcium phosphate samples with the lead ion are considered. As distinct from mesoporous samples, samples with a mixed pore structure dominated by large and medium-sized pores are highly reactive toward the lead ion.     

Effect of parameters of a crosslinked polyacrylic matrix on the impregnation of photoactive compounds in supercritical fluids

The effect of the network density of spatially crosslinked polyacrylic transparent matrices and the conditions of their impregnation with a photochromic compound via the use of supercritical carbon dioxide on the concentration of the introduced photochromic compound of the spiroxazin family is studied. The concentration of impregnated filler in a matrix is shown to increase with increases in the interjunction distance (below a certain level) and network chain flexibility as well as with increases in the temperature and pressure of the impregnation process. Impregnation in rigid networks occurs only in surface layers, whereas, in an elastic network, impregnation occurs in the entire volume of a sample. Matrices based on oligourethanemethacrylates are characterized by a good thermodynamic affinity toward spiroxazin photochromic compounds, a fact that makes it possible to increase the concentration of photochromic compounds in the matrix up to 3 wt % under conditions of supercritical impregnation. The photochromic characteristics of an impregnated compound are shown to be preserved in samples.     

UV-radiation-induced formation of gold nanoparticles in a three-dimensional polymer matrix

The possibility of generation of a surface plasmon resonance by gold nanoparticles in a 3D network polymer matrix upon irradiation of a liquid acrylic composition containing a dissolved Au³⁺ salt is demonstrated for the first time. UV-irradiation of the solution simultaneously causes gold photoreduction to Au⁰ and acrylate photopolymerization. The possibility of preparing transparent colorless films that, when heated or exposed to light, give rise to a visible-spectrum absorption band belonging to a plasmon resonance of metal nanoparticles is demonstrated. The intensity and position of the plasmon resonance band depend on the parameters of the 3D polymer network, chemical structure of the oligomer, type of the support, and conditions of formation of Au⁰ particles. The formation of reduced gold nanoparticles responsible for the plasmon resonance band occurs more effectively in low-density networks with a large interchain length and containing oligomer block capable of complexation with the metal. The formation of nanoparticles is affected by the chlorine-containing products of the reduction of the gold salt.     

Synthesis of the N,S-acetals of diacyl- and alkoxycarbonyl(acyl)ketenes with β-dicarbonyl compounds,organic thiocyanates,and nickel(2+) complexes

An effective method is proposed for the production of the N,S-acetals of diacylketenes and acyl(alkoxycarbonyl)ketenes, based on the addition of methylene-active-diketones and-ketoesters to alkyl and aryl thiocyanates catalyzed by Ni(2+) acetylacetonate. Methods are indicated for the synthetic utilization of diacetylketene N,S-acetals and include their conversion to ketene aminals, chelation with boron compounds, and deacylation of derivatives of monoacetylketene with methanol in the presence of Co(2+) acetate.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2600–2605, November, 1991.     

Deironing of Water with Natural Carbonate-containing Tripoli

The possibility of using natural carbonate-containing tripoli for water deironing was studied. Factors are considered determining the efficiency of tripoli in Fe(III) absorption.     

Reactions of triethylborate with amines

Russian Chemical Bulletin -