Light-scattering detection with a fluorimetric detector in high-performance liquid chromatography

Non-fluorescence compounds were detected by a fluorescence detector based on scattering light. The fluorescence detector was used without any modification, and the scattering light was observed at the wavelength twice as long as the excitation wavelength. Actually the wavelength of the observed scattering light was the same as that of the excitation light. The maximum signal was achieved at around 280 nm. The signal was increased with increasing molecular weight or size of analytes. Colloidal silica with nanometer sizes, ethylene glycol oligomers, saccharides and cyclodextrins could be visualized by the present detection method. The detection limit at S/N=3 for colloidal silica with 78 nm was 39 pg for 20-microL injection.     

γ-Irradiated Ni-hesperidin nanocomposite for selective trace-level sensing of sulfide ions

Journal of Radioanalytical and Nuclear Chemistry - Synthesis of 5-(4-aminophenyl)-10,15,20-triphenyl porphyrin (B) was performed using the Lindsey method and characterized by 1H NMR. Cu-porphyrin...     

Light-scattering and turbidimetric detection of silica colloids in size-exclusion chromatography

Silica colloids were separated by size-exclusion chromatography and monitored by fluorimetric and UV detection. In the former means of detection, silica colloids were visualized by light-scattering. The signal intensity based on the light scattering increased with increasing size of the silica colloids. The maximum intensity was observed at excitation wavelengths around 270–290nm. In UV detection, silica colloids were visualized based on turbidimetry, and the signal intensity also increased with increasing size of the silica colloids and with decreasing detection wavelength. The signal intensities for both light-scattering and turbidimetric detection were a linear function of the concentration of the silica colloids. The detection limit at S/N = 3 for 78-nm colloids was 0.06 ppm for light-scattering detection whereas the LOD was 2.3 ppm for UV detection. Effects of mobile phase conditions and flow rate on resolution and peak shape were examined. Use of phosphate buffer allowed the separation of silica colloids of different sizes in size-exclusion chromatography.     

Synthesis and biological activity of 3,5-diacetyl-2,6-dimethylpyridine derivatives

Chemistry of Heterocyclic Compounds - Aldol-crotonic condensation reactions of 3,5-diacetyl-2,6-dimethylpyridine with various aldehydes were used to synthesize bisazachalcone derivatives, which...     

Efficient Photooxidation of Aryl(hetaryl)pyrazolines by Benzoquinone

Photooxidation of aryl(hetaryl)pyrazolines in the presence of benzoquinone has been studied in organic solvents. This reaction occurs at high rate to provide the corresponding pyrazole in a good yield. The effects of the solvent, pyrazoline structure and oxygen provide definite information on the reaction pathway. It appears that radical species are intermediates in the photooxidation of aryl(hetaryl)pyrazolines in the presence of benzoquinone. A comparison of the new results with the photooxidation of aryl(hetaryl)pyrazolines in the presence of perchloroalkanes is also discussed.     

Multicomponent synthesis of unsymmetrical 5-nitropyridines

Chemistry of Heterocyclic Compounds - Reaction of 2-nitroacetophenone, furfurol, β-dicarbonyl compounds, and ammonium acetate led to 3-substituted...     

Structure of diisopropylammonium dicitratoborate and crystallochemical features of alkylammonium complexes with boric and citric acids

Single crystals of diisopropylammonium dicitratoborate of the formula (C₃H₇)₂NH₂[(C₆H₆O₇)₂B] (I) were prepared and characterized by X-ray diffraction. The crystals are monoclinic, space group C2/c, a = 15.9978(5) Å, b = 11.0805(4) Å, c = 13.1872(4) Å, α = 90°, β = 103.34(1)°, γ = 90°, Z = 8, V = 2274.5 (1) Å ³, Z = 8, ρ_calc = 1.440 g/cm³, 2237 reflections with I > 2σ(I); R1 = 0.0408. Structure I is built from complex spiran-type dicitratoborate anions and diisopropylammonium cations. In the crystal packing, the anions and the cations form staggered stacks linked by a system of hydrogen bonds involving three independent contacts O(N)-H...O. X-ray diffraction data for structure I were compared with those for complexes of boric and citric acids with ammonium and alkylammonium cations.     

Effects of preparation temperature on the conductivity of polypyrrole conducting polymer

An attempt has heen made to investigate the effect of temperature on the conductivity of polypyrrole conducting polymer films prepared by an electrochemical method in an aqueous medium using camphor sulfonate as the dopant. The polymer was grown from aqueous solutions employing a range of temperatures (l–60°C). It was found that with increase in temperature the conductivity decreased and the optimum temperature was found to be between 10 and 30°C. The results showthatthe polymer formed at low temperature has higher conductivity and is stronger than that formed at higher temperatures. Characterization by X-ray scattering shows that interlayer distance, d_Bragg (?), increases with increasing temperature. The morphology of the films formed was studied by using a scanning electron microscope (SEM). The changes in conductivity and physical appearance were interpreted as being due to compactness in the molecular packing and formation ofαβ linkages in the film.