Fluorometric Determination of Trace Amounts of Fluoride Ion Using an Expanded Porphyrin

A highly selective and sensitive method of fluorometry is described for determination of the fluoride ion at the parts per billion level via the ion-pair complex formation of the fluoride ion with an expanded prophyrin [2,23-diethyl-8,17-bis(2-ethoxycarbonylethyl)-3,7,12,13,18,22-hexamethylsapphyrin (H₃sap)]. The ion-pair complex gives out an enhanced fluorescence intensity at 680 nm on excitation at 450 nm. Since the present method is based on a direct reaction of the fluoride ion with the sappyrin, a 200-fold amount of the aluminum (III) ion [10⁻⁴M (M = mol dm⁻³)] and a 2000-fold amount of the iron(III) ion (10⁻³M) over the fluoride ion did not interfere with determination of the fluoride ion at concentrations as low as 5 × 10⁻⁷M in the presence of 1,2-diaminocyclohexane-N,N,N′,N′-teraacetic acid. The proposed method was applied to determination of the fluoride ion in various water samples (tap water, river water, rain water, underground water, and hot spring water) and satisfactory results were obtained.     

Condensed thienopyrimidines. II. Synthesis and gastric antisecretory activity of thiazole and polymethylene condensed thienopyrimidine derivatives

Thiazolo[3,2-a]thieno[3,2-d]-, [3,4-d]- and [2,3-d]pyrimidin-5-one derivatives (6, 11 and 16), and polymethylene condensed thieno[3,2-d]-, [3,4-d]- and [2,3-d]pyrimidin-5-one derivatives (19-21), in which the oxygen atom of the oxazolidine moiety in 3 was replaced by a sulfur atom or methylene groups, were synthesized and evaluated for gastric antisecretory activity in pylorus-ligated rats. The structure-activity relationships of these compounds are discussed.     

Radiation-induced copolymerizations of perfluorovinyl acetic acid and its methyl ester with α-olefin

Homopolymerizations and copolymerizations of perfluorovinyl acetic acid (FVA) and its methyl ester (MFVA) were carried out by γ radiation at a temperature of 25°C, a dose rate of 1 × 10⁶ rad/hr, and FVA/α-olefin and MFVA/α-olefin ratios of 10/90-90/10 in the monomer mixture. FVA and MFVA gave small quantities of brown and greasy low-molecular-weight homopolymers. The polymerization rates of both FVA and MFVA were extremely small, as shown by the maximum G value of monomer consumption of 12. FVA and MFVA reacted with α-olefin to form waxlike copolymers. The copolymerization rates of both FVA and MFVA with α-olefin were remarkably larger than those of the homopolymerizations, particularly with ethylene. The polymer compositions of FVA/ethylene or MFVA/ethylene was nearly 1/2 over a wide range of the monomer compositions. The Mayo–Lewis method gave negative r₁ (FVA) and r₁ (MFVA). The polymer composition curves could be well interpreted by introducing the penultimate model.     

Pre-irradiation induced grafting of styrene into crosslinked and non-crosslinked polytetrafluoroethylene films for polymer electrolyte fuel cell applications. II: Characterization of the styrene grafted films

Crosslinked and non-crosslinked polytetrafluoroethylene films (RX-PTFE and V-PTFE films, respectively) were irradiated by γ-ray and then grafted with styrene in liquid phase. Microscope FT-IR spectroscopy, TGA, solid state ¹³C CP/MAS and high resolution HS/MAS NMR spectroscopy, wide-angle X-ray diffraction (WAXD) study were used to get the structural information of the styrene grafted RX-PTFE and V-PTFE films. From microscope FT-IR spectra of the grafted RX-PTFE films, the “grafting front mechanism” was proved. TGA analysis showed that the grafted films have a small degradation step and two main degradation steps. In the ¹³C CP/MAS NMR spectra of the non-grafted films, there are no signal due to the absence of the hydrogen atom. While in the spectra of the grafted films, there are signals attributed to the polystyrene grafts. In the ¹³C HS/MAS NMR spectra of the grafted films, the relative intensity of the peaks attributed to the polystyrene grafts increased while the relative intensity of the peak attributed to PTFE matrix decreased with the increase in the DOG. From WAXD patterns, the intensity of the crystalline peak decrease with the increase in the DOG. The grafted films were sulfonated by chlorosulfonic acid and the results of highest IEC value exceeded 3.0. Those results will be reported in the near future.     

Improving the properties of the proton exchange membranes by introducing α-methylstyrene in the pre-irradiation induced graft polymerization

New proton exchange membranes (PEMs) were prepared by pre-irradiation induced grafting of α-methylstyrene (AMS)/styrene (STY)/divinylbenzene (DVB) into the crosslinked polytetrafluoroethylene (RX-PTFE) films and successively sulfonated. The new PEMs showed the improved glass transition temperature and chemical stability as compared with the PEMs prepared by pre-irradiation induced grafting of STY/DVB. The balance of the cost, grafting kinetic, thermal properties and the properties of the resulted proton exchange membrane is the key point of this work.     

Potential acting on the trapped electron

If the absorption of a trapped electron can be shown to correspond to bound—free transitions, it should be possible to calculate the potential acting on the trapped electron inversely from its absorption spectrum. In this paper we present the method of calculating the potential acting on a trapped electron from the observed absorption spectrum.     

Spectrophotometric determination of lithium ion using a water-soluble octabromoporphyrin in aqueous solution

A water-soluble porphyrin, (2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin; H(2)obtpps(4-)) was synthesized and developed for the determination of lithium ion in aqueous solution. The octabromo groups lower the basicity of the porphyrin by their electron-withdrawing effect, and enable the porphyrin to react with the lithium ion in alkaline solution to form the lithium complex along with a shift of absorption maximum: lambda max/nm (logepsilon/mol(-1) dm(3) cm(-1)) of the lithium porphyrin are 490.5 nm (5.31) and 734 nm (4.36). Sodium and potassium ions did not react with the porphyrin. The equilibrium constant for the reaction Li(+)+Hobtpps(5-)right harpoon over left harpoon[Li(obtpps)](5-)+H(+) was found to be 10(-8.80) and the conditional formation constant of the [Li(obtpps)](5-) at pH 13 is 10(4.21). The above results were applied to the determination of lithium ion in aqueous solution. The interference from transition and heavy metal ions was masked by using N,N'-1,2-ethanediylbis[N(carboxylmethy)glycinato]magnesium(II) ([Mg(edta)](2-)) solution. Absorbance at 490 nm was measured against a blank solution. A calibration graph was linear over the range of 0.007-0.7 mug cm(-3) (1x10(-6)-1x10(-4) mol dm(-3)) of lithium(I) with a correlation factor of 0.967. Lithium ion less than ppm level was determined spectrophtometrically in aqueous solution. The proposed method was applied to the determination of lithium in human serum and sea water samples.     

Main-chain scissions of poly(methyl methacrylate) induced by chlorinated nitrosobenzenes as radical generators

The spin trap agent, 2,6-di-chloronitrosobenzene (DCNB), which is decomposed into a nitrogen monoxide and a chlorinated phenyl radical on slight warming, was known to act as a radical generator through hydrogen abstraction by the chlorinated phenyl radical from an adjacent molecule. An ESR spectrum was observed at room temperature from a poly(methyl methacrylate) (PMMA)-benzene solution after the addition of DCNB followed by a warming to ca 30°C. The radical concentration increased with time. The spectrum was assigned to the spin adducts of PMMA radicals generated and trapped by DCNB. Analyses of the spectra observed from normal PMMA and partially deuterated PMMA's indicated that the majority of the PMMA radicals were the chain-scission species

and a minority were

. It was concluded that the main-chain scissions in PMMA were caused by the radicals (D), which had been primarily produced by the chlorinated phenyl radicals. These ESR data are supported by the fact that a decrease in molecular weight of PMMA was observed after addition of DCNB, and further reinforced by the fact that a molecular weight estimated from the number of the scission radicals agreed fairly well with the measured molecular weight. Similar results were obtained when both tri-chlorinated nitrosobenzene and tetra-chlorinated nitrosobenzene were used instead of DCNB.     

Reflection of electrons and photons from solids bombarded by 0.1 - to 100-MeV electrons

Electron and photon reflection ratios (in number and energy) for absorbers bombarded by electrons have been computed with the ITS Monte Carlo system version 3. Electrons of energies from 0.1 to 100 MeV have been assumed normally incident on an effectively semi-infinite absorber. The absorbers considered are elemental solids of atomic numbers from 4 to 92. The data on the electron reflection ratios agree rather well with the experimental data collected from literature except some discrepancies when the number-reflection ratio is small. For photons, the number-reflection ratio increases with increasing energy, but the energy-reflection ratio shows a maximum around 10 MeV. Empirical equations for the electron reflection ratios and the photon energy-reflection ratio are given (for electrons, graphs only).     

19F- and 1H-NMR spectra of tetrafluoroethylene–propylene copolymers

High resolution 94-MHz ¹⁹F- and 100-MHz ¹H-NMR spectra were measured on a series of tetrafluoroethylene (TFE)-propylene (P) copolymers having a range of composition (TFE/P molar ratio = 37/63–55/45) and polymerized at different temperatures (?23, 25 and 65°C). The spectra were analyzed in relation to copolymer compositions. The assignment of ¹⁹F resonance in terms of tetrads proposed previously was confirmed, and the tentative assignment of ¹H resonances was proposed in terms of triads. The spectra thus interpreted revealed the sequence distribution of the copolymers. Copolymer compositions calculated from NMR spectra and elemental analysis agreed rather well with each other. Monomer reactivity ratios were calculated from the sequence distributions and compared with those obtained from the elemental analysis. It was observed that highly alternating copolymers are obtained in this system over a wide range of monomer composition at lower temperatures and that a deviation from alternancy increases slightly with rising polymerization temperature.