Temperature-induced crystallization and compactibility of spray dried composite particles composed of amorphous lactose and various types of water-soluble polymer

The purpose of this study was to investigate the temperature-induced crystallization and the compactibility of the composite particles containing amorphous lactose and various types of polymers. The composite particles were prepared by spray-drying an aqueous solution of lactose and various types of gel forming water-soluble polymers at various formulating ratios. The stabilizing effect of hydroxypropylcellulose (HPC) and polyvinyl pyrrolidone (PVP) on amorphous lactose in the composite particles was smaller than that of sodium alginate in comparing at the same formulating ratios. The difference in the stability of amorphous lactose in the composite particles was attributed to the difference in the glass transition temperature (Tg) of the composite particles caused by the polymers formulated. The tensile strength of compacted spray-dried composite particles containing the polymers was higher than commercial lactose for direct tabletting (DCL21). The tensile strength of the composite particles was increased with an increase in water content in the particles. The difference in compactibility of the composite particles containing the different amount of polymer and water could be explained by the difference in Tg of the particles.     

A hydrogen-bonding receptor that binds cationic monosaccharides with high affinity in methanol

A dicarboxylate host (1) binds cationic monosaccharides such as D-glucosamine HCl (2), D-galactosamine-HCl (3), and D-mannosamine-HCl (4) with high affinity (K1 = 8.0 x 10(4)-2.0 x 10(5) M(-1)) in methanol. In circular dichroism (CD) spectroscopy a positive exciton-coupling band was observed near 290 nm; this indicates that the saccharides are recognized by multiple point interactions. Since the corresponding neutral monosaccharides are not significantly bound, one may conclude that complex formation is primarily due to the electrostatic interaction between NH3+ in the guest and one carboxylate in the host and secondarily due to hydrogen-bonding interactions of OH groups with the other carboxylate and/or nitrogen bases. Molar ratio plots and Job plots indicate that host 1 and cationic monosaccharide guests form CD-active, pseudo-cyclic 1:1 complexes at low guest concentration followed by the formation of CD-silent, acyclic 1:2 1-saccharide complexes at high guest concentration. The possible binding modes are discussed in detail on the basis of molecular mechanics calculations and chemical shift changes in 1H NMR spectra. The results of competition experiments with several cationic reference compounds bearing fewer OH groups than 2-4 are consistent with the proposed binding model. Thus, the present study is a rare example of saccharide recognition in a protic solvent, where in general, hydrogen-bonding interactions are rarely useful because of strong solvation energy. These are apparently the strongest saccharide complexes involving noncovalent interactions between host and guest. We believe that the findings are significant as a milestone toward development of new saccharide recognition systems ultimately useful in aqueous solution.     

VISUAL PIGMENTS—10. SPECTROSCOPY AND PHOTOPHYSICAL DYNAMICS OF RETINOL AND RETINYL ETHER

Abstract— The absorption and emission spectra, lifetimes and quantum yields of all-trans retinol have been examined as a function of solvent and temperature. In addition, the spectroscopy of retinyl ether and 2 other polyene alcohols have been determined. Based on the results obtained, we conclude that the singlet excited state of retinol and retinyl cther is of a forbidden character and of the type loosely called ¹A^-_g. Retinol forms a dimer in an alkane solvent when cooling from 298 to 77 K. A general structure for the dimer is proposed.     

Determination of237Np in environmental samples using inductively coupled plasma mass spectrometry

Ammonium uranates (AU) obtained by the addition of aqueous NH₄ OH to a solution of UO₂ (NO₃)₂ or the equilibrium reaction of UO₃ · 2H₂ O with the vapour over concentrated NH₄ OH have been studied by X-ray diffraction (XRD) analysis, diffuse reflectance Fourier transform infrared spectrometry (DR-FTIR) and chemical analysis. Ammonia can be present as either NH₃ or NH ₄ ⁺ . For precipitates obtained at a pH of 3.7, ammonia in the form of NH₃ is predominant. For ammonium uranate obtained by reaction over concentrated NH₄OH, most of the ammonia is bonded as NH ₄ ⁺ . The reaction mechanism and structures of the products are also discussed.     

Enantiomeric purity determination of malic acid in apple juices by multi-beam circular dichroism detection

A multi-beam circular dichroism (CD) detector which is easily constructed by inserting inexpensive optics into a conventional photo-diode array detector has an advantage of simultaneous detection of the absorbance and CD. The enantiomeric purity determination of malic acid in beverages was performed by this detection system. Malic acid when complexed with Cu(II) was found to have an absorbance maximum at around 750 nm. The L-malic acid-Cu(II) complex showed a positive Cotton effect in its absorbance band and its anisotropy factor (delta epsilon/epsilon) was relatively large at about 1/170. This complex was retained on a reversed-phase column with the addition of racemic 2-hydroxy-3-methylbutyric acid to the mobile phase as the ligand. A plot of the relative peak areas between the CD and the absorption (delta abs/abs) versus optical purity showed good linearity with a correlation coefficient of 0.999, and the precision expressed as the relative standard deviation of the errors from the regression line was +/-2.7% (2sigma). The accuracy of the proposed method was assessed by capillary electrophoresis. Eight commercially available juice products were analyzed using this method. Five of them were thought to be adulterated with synthetic malic acid.     

A characteristic effect of pressure on inclusion complexation of phenothiazine dyes with p-sulfonatocalix[6]arene in a room-temperature ionic liquid

The inclusion complexation of p-sulfonatocalix[6]arene (Calix-S6) with three kinds of phenothiazine dyes was studied spectrophotometrically in a mixture of a room-temperature ionic liquid [bmim]BF₄ (1-butyl-3-methylimidazolium tetrafluoroborate) and ethanol. We have determined the association constants of Calix-S6 with phenothiazine dyes under external static pressure up to 767 bar in the [bmim]BF₄-ethanol and alcohol-water mixtures. With increasing external pressure, the inclusion equilibrium in the alcohol-water mixtures was shifted to the dissociation side. Conversely, the inclusion equilibrium of methylene blue (MB) and azure A (AA) in the ionic liquid mixture was shifted to the association side. From the analysis of the pressure effects, the reaction volumes ΔV for inclusion complexation were estimated as −7 to 9 cm³ mol⁻¹ in the [bmim]BF₄-ethanol mixture and 20–32 cm³ mol⁻¹ in the alcohol-water mixtures. Based on the results, we have suggested that there is a competing complexation between the included dye and [bmim]BF₄ molecules in the ionic liquid.