粉煤灰与几种酸固相反应特性的表面分析

用扫描电镜．能量色散谱研究了粉煤灰与酸的固相反应过程中表面形貌和化学组成变化特性。室温下粉煤灰分别与HCI、HNO3、H2SO4、HCIO4固相反应后，表面产生直径20—200nm的结晶颗粒或晶柱。反应生成的水溶物结晶体的扫描电镜图像分别呈手指状、龟背形、蛛蛛状、蝙蝠态，分别为氯化铝铁混晶、硝酸铝铁混晶、硫酸铝铁混晶和高氯酸铝铁混晶。粉煤灰是硅、铝、铁等元素的氧化物聚集体，铁铝等氧化物主要分布在颗粒表面，氧化硅主要分布在颗粒内层。用少量酸进行固相反应这些氧化物聚集体可相互剥离，用H2SO4处理粉煤灰优先将铁铝氧化物转化成可溶性硫酸盐。     

The use of glass capillary columns for the analysis of polar natural products

Two published procedures for glass capillary column production are applied to produce capillaries for chromatography of polar natural compounds. Soda lime glass capillaries, after leaching with aqueous HCL, are either treated with colloidal silicic acid or with barium carbonate and coated with either Silar 7CP or SE 52. A test mixture as well as polar carbohydrate and peptide mixtures are chromatographed on the different columns and their chromatographic properties are evaluated. Combined capillary gas chromatography-electron impact and chemical ionization mass spectrometry are used for identification of the peptide sequence.     

Benefits of X-Ray Spectrum Simulation at low Energies

 There are particular benefits in spectrum simulation for the interpretation of characteristic X-ray peaks below about 2 keV in energy, where peak overlaps, a sloping background and changing detector efficiency make it difficult to measure true peak intensities. Despite these difficulties, we have shown that a useful accuracy of simulation is possible without major revision of the existing theory, allowing the electron microprobe user to compare on-line a measured spectrum with one synthesised from an assumed sample composition. As part of a wider study, we have used a database of X-ray spectra from 150 samples of known composition to confirm the accuracy of simulation over the energy range from 0.28–1.9 keV, finding an RMS error of better than 8%. The database included 181 Kα, Lα and Mα peaks from elements of atomic number 6–77, excited by beam voltages from 5–30 kV. Central to the method is the use of the ratio of (Peak Intensity)/(Total Background Intensity), which allows spectra to be compared from instruments of differing collection efficiency, thereby easing the collection of data over a wide range of conditions. Examples are given to illustrate the use of the simulator in helping to choose the best conditions for analysis, and as an aid in interpreting the spectra so obtained. Both modes of operation are iterative in nature and require a fast and accurate simulator that is easy to use. Further development will be guided by experience in its use.     

Single-crystal 2H NMR of deuterated 1,10-decanedicarboxylic acid included in hydrogenated urea channels

The intergrowth of 1,10-decanedicarboxylic acid and urea give infinite hydrogen-bonded chains of the guest included in the hexagonal urea host. A deuterium high-resolution solid-state NMR study of the selectively deuterated intergrowth compound 1,10-decanedicarboxylic acid/hydrogenated urea at variable temperature in the range 90 < or = T < or = 300 K was performed on a single crystal. The analysis of the second moment as a function of temperature is shown to be compatible with the known phase transition occurring near T(c) = 203 K. Moreover, the spectra indicate that the orientational disorder is strong, and is compared to an axial uniform disorder. For this purpose, the general equation for the second moment of a system with uniform two-dimensional axial orientational disorder is given, and a method to take into account the non-uniform excitation of the pulse sequence is proposed.     

The use of TG-FTIR technique for the assessment of hydrogen bromide emissions in the combustion of BFRs

The TG-FTIR technique was used in the present study to investigate the thermal degradation behaviour of materials containing brominated flame retardants under fire conditions. Time-temperature profiles and oxygen concentrations typical of selected fire scenarios were reproduced in the thermogravimetric analyzer, while the characterization of the gaseous products generated was performed by the simultaneous FTIR analysis. FTIR analysis combined with the use of specific calibration procedures allowed the quantitative estimation of the gaseous products evolved as a function of experimental conditions. The results obtained allowed the straightforward assessment and the comparison of the quantities of hydrogen bromide formed in the oxidation and thermal degradation of pure brominated flame retardants and of flame retarded materials of industrial interest. Hydrogen bromide yields resulted dependent on the experimental conditions used, such as oxygen concentration and heating rate. Although TG-FTIR experiments only provide a representation of the actual heterogeneous combustion products in real fire conditions, the coupled TG-FTIR technique proved to be a straightforward experimental methodology allowing one to obtain reference data on the nature and quantities of the macropollutants generated in a fire. This revised version was published online in July 2006 with corrections to the Cover Date.     

Monitoring nitrite with optical sensing films

A new, low-cost nitrite sensor was developed by immobilizing a direct indicator dye in an optical sensing film for food and environmental monitoring. This sensor was fabricated by binding Safranine O to a cellulose acetate film that had previously been subjected to an exhaustive base hydrolysis. The membrane has good durability (>12 months) and a short response time (<8 s). Nitrite can be determined for the range of 0.005-2.00 μg ml⁻¹ with 3δ detection limits of 0.001 μg ml⁻¹. The method is easy to perform and uses acetylcellulose as a carrier. The reagents used for the activity of the cellulose support are inexpensive, non-toxic and widely available.     

1,3-Dipolar cycloaddition in the synthesis of pyrazolyl-substituted nitronyl nitroxides

A new approach to the synthesis of polyfunctional pyrazolyl-substituted nitronyl nitroxides was developed based on the presynthesized pyrazole derivatives prepared by 1,3-dipolar cycloaddition. The structures of the resulting mono-and biradicals were confirmed by X-ray diffraction. Dedicated to Academician A. L. Buchachenko on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2105–2116, September, 2005.     

Conformational analysis 29: Preparation and1H and13C NMR,FTIR, MS,and crystallographic conformational and configurational study of 3-Oxo-1,3-oxathiane and its monomethyl derivatives

3-Oxo-1,3-oxathiane (1) and its monomethyl derivatives were prepared by oxidation of the corresponding 1,3-oxathianes. The structural analysis was carried out by¹H and¹³C NMR, FTIR, and mass spectrometry. At 298 K compound1 was a 1 1 (at 173 K a 3 1) mixture of the SO(ax) and SO(eq) chair forms. The major oxidation products of methyl 1,3-oxathianes attained exclusively the SO(ax), Me(eq) chair forms except that of the 5-methyl derivative, which consisted of 7% of the SO(eq), Me(ax) chair conformation in CDCl₃ solution. The minor products of oxidation existed in anancomeric SO(eq), Me(eq) chair conformations. The oxidation of 2-methyl- 1,3-oxathiane, however, led to 3,3-dioxo derivative (6) in addition to thetrans [SO(eq)] monoxide. The crystal structures of6 andtrans-3-oxo-5-methyl-1,3-oxathiane were solved by X-ray diffractometry.