非水体系毛细管电泳-紫外检测法测定苯甲酸和苯甲醛

建立了用非水相体系高效毛细管电泳-紫外检测法同时测定苯甲酸和苯甲醛的新方法，考察了运行电压、非水相介质和电解质等因素的影响，在25℃下，以V（乙腈）：V（碳酸丙烯酯）=1：1的混合液为溶剂，缓冲体系中含15mmol／L十六烷基三甲基溴化铵体积分数1％乙酸，重力进样30S，运行电压20kV，毛细管总长45cm有效长度30cm，φ75μm，检测波长285nm。苯甲酸线性范围为5～40μg／mL，线性方程为：Y=13．473ρ＋13．336，相关系数r=0．9985，检出限为0．92μg／mL，RSD为3．8％。苯甲醛的线性范围75～1125μg／mL线性方程为：Y=5．2449ρ＋564．01，相关系数r=0．9997，检出限为15．60μg／mL，RSD为3．5％。已用于经空气氧化后的苯甲醛中苯甲酸和苯甲醛的测定。     

Basicity of 2-phenyl-5-R-1,3,4-oxadiazoles

We have studied the basicity of 2-phenyl-5-R-1,3,4-oxadiazoles (R = H, Me, CH₂Ph, t-Bu, CH₂Cl, CCl₃, CF₃) in aqueous sulfuric acid solutions. These compounds are weak organic bases (pK_BH ⁺ is −1.8 to −5.2). The values of pK_BH ⁺ determined on the H₀ and X acidity function scales agree well with each other. The substituent at the 5 position has a substantial effect on the basicity of the 1,3,4-oxadiazole ring. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 748–756, May, 2006.     

Selective degradation of lignin and elimination of HO radicals in pulps by O<Subscript>3</Subscript> and UV laser flash irradiation

HO^. radical is an aggressive reagent to abstract hydrogen from diverse substitutes and lead them to degradation, however, in reaction of active oxygen species with lignins, complex phenolic polymers, in dispersed lignocellulose such as pulp for environment-benign delignification, HO^. radicals should be eliminated as more as possible to prevent cellulose from unfavorably concomitant degradation. A reaction system of O₃ is constructed under UV laser flash irradiation, and HO^. radicals are controlled efficiently by it. A new mechanism is proposed, for the first time, that O^. radicals generated from reaction of O₃ with UV laser flash irradiation might be the contributor to scavenge HO^. radicals.     

The Influence of Sulfate‐Doping on the Nature of V Sites in VOx/TiO2 Catalysts

EPR, UV/Vis and FTIR spectroscopy as well as thermal analysis (TA/MS) were applied to study the influence of sulfate species present in the anatase support on the specific nature of VO_x species in supported VO_x/TiO₂ catalysts. Those sulfate species modify the local structure of the supported vanadyl species and lead to the formation of two types of VO²⁺ sites instead of only one type being formed on sulfate‐free anatase. EPR and FTIR spectroscopic measurements revealed that a part of the VO²⁺ species are directly bound to the surface sulfate species. By TA/MS it was found that SO₂ is released at lower temperature from VO_x/TiO₂ in comparison to the vanadium‐free support. The direct bonding between sulfate and VO_x species stabilizes the latter on the surface of VO_x/TiO₂ resulting in three effects: 1) a higher V site dispersion in comparison to sulfate‐free TiO₂, 2) a better resistance of surface vanadyls against diffusion into the bulk of the support and 3) a much faster reoxidation of reduced V sites than observed on sulfate‐free TiO₂.     

The Diels-Alder reaction between substituted 6,6-dimethyl-2-vinylnorpinenes and maleic anhydride

Cycloaddition of substituted 6,6-dimethyl-2-vinylnorpinenes with maleic anhydride occursvia the attack of a dienophile on diene from the less hindered side of the bicyclic fragment. IR, UV, CD, and¹H NMR spectra of adducts have been studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1546–1548, August, 1995.The authors are grateful to I. E. Ismaev for recording several¹H NMR spectra.     

The self-organization properties of <Emphasis Type="Italic">n</Emphasis>-dodecylammonium α-glutamate/<Emphasis Type="Italic">n</Emphasis>-C<Subscript>5</Subscript>H<Subscript>11</Subscript>OH/water system

A biocompatible surfactant-n-dodecylammonium α-glutamate (GDA) with biodegradable and biocompatible properties was synthesized, and the phase behavior and the structural properties of GDA/n-pentanol/water system was studied by small-angle X-ray diffraction, electron spin resonance, and freeze-fracture transmission electron microscopy (FF-TEM). In the ternary phase diagram of GDA/n-pentanol/water system, there exist three isotropic regions—O/W, bicontinuous, and W/O structures, and two anisotropic regions—hexagonal liquid crystal (HEX), and lamellar liquid crystal (LLC) regions. UV irradiation causes the decrease in the interlayer space, d, of lamellar liquid crystal and in the radius, r, of column aggregates of hexagonal liquid crystal, but it has little effect on the structure of O/W and W/O microemulsions.     

Synthesis of metal/polymer nanocomposite by UV-radiation curing

Nanocomposite polymers containing bismuth nanoparticles (2 wt%) have been obtained by photopolymerization of acrylic resins. The bismuth nanoparticles have been synthesized by reduction of BiCl₃ with t-BuONa activated sodium hydride. In situ t-BuONa stabilization protects the metallic particles against aggregation. Transmission electron microscopy (TEM) analysis has shown that the bismuth nanoparticles are well dispersed in the acrylic resin. The curing process was followed quantitatively by infrared spectroscopy through the decrease upon UV exposure of the IR bands characteristic of the functional groups. The bismuth nanoparticles were found to have no detrimental effect on the photopolymerization kinetics. Dynamic mechanical analysis (DMA) has shown that the viscoelastic properties of the nanocomposite photopolymer are significantly modified in comparison with corresponding UV-cured polymer. The addition of metal nanoparticles was found to greatly reduce the gloss of UV-cured coatings.     

Sequential injection analysis for benzophenone-4 and phenylbenzimidazole sulphonic acid in sunscreen sprays by solid-phase extraction coupled with ultraviolet spectrometry

A sequential injection UV method was developed to determine benzophenone-4 (BZ4) and phenylbenzimidazole sulphonic acid (PBS) simultaneously, these being the most commonly used UV-filters in aqueous formulations used as sunscreen sprays. The selective elution of both was performed by on-line solid-phase extraction, by retention on a SAX microcolumn and separation by varying the pH of elution. The sensitivity obtained was 0.042±0.001 ml μg⁻¹ for PBS and 0.0159±0.0003 ml μg⁻¹ for BZ4. The limit of detection was 1.6 μg ml⁻¹ for PBS and 0.6 μg ml⁻¹ for BZ4. The R.S.D. of the results was 1-6% for PBS and 1-12% for BZ4. The method was validated using commercial sunscreen formulations with concentrations determined by a liquid chromatographic procedure. The two procedures gave comparable results. Automation of the method means the amount of reagents used and residues generated are decreased. The system allows the required analysis sequence to be programmed using suitable software.     

Migration of Ethylene Terephthalate Oligomers from Roasting Bags into Olive Oil

Summary A high-performance liquid-chromatographic method with UV detection (HPLC–UV) has been developed for quantification of ethylene terephthalate oligomers in olive oil, from which they were extracted with acetonitrile. Oligomers, from monomers (M₁) to pentamers (M₅), were jointly and/or individually identified by liquid chromatography with mass spectrometry (electron-impact mass spectrometry (EIMS) low- and high-resolution) and were quantified by HPLC–UV using an acetonitrile solution of the major oligomer (the trimer M₃) as standard. For M₃ recovery was 98.9%, the detection limit was 60 g L^–2, and method precision was 2.03% (RSD). Migration of oligomers M₁–M₅ into 50 mL olive oil sealed in each of two brands of 10 cm × 10 cm poly(ethylene terephthalate) roasting bag was evaluated under two sets of conditions that approached but remained below the limit at which the bag material became physically deformed – heating for 7 min at 850 W in a microwave oven, or for 60 min at 200 °C in a conventional oven. Total migration was approximately 2.7 mg dm^–2 under the former conditions and 3.5–4.1 mg dm^–2 under the latter.Presented at the International Symposium on Separation and Characteristics of Natural and Synthetic Macromolecules, Amsterdam, The Netherlands, February 5–7, 2003