ascorbic-acid and triethanolamine

Cysteine and triethanolamine capped CdTe nanoparticles have been synthesized using a simple aqueous solution based method. This method involves the reaction of tellurium powder with sodium borohydride (NaBH(4)) in water to produce telluride ions (Te(2-)), followed by the simultaneous addition of an aqueous solution of cadmium chloride or other cadmium source (acetate, carbonate and nitrate) and solution of L-cysteine ethyl ester hydrochloride or triethanolamine. The effect of capping agent on the size, structure and morphology of the as-synthesized nanoparticles was investigated. The particles were characterized using optical spectroscopy, transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy.

Topics: Ascorbic Acid; Borohydrides; Cadmium; Cadmium Compounds; Cysteine; Ethanolamines; Indicators and Reagents; Luminescence; Microscopy, Electron, Transmission; Nanoparticles; Particle Size; Spectrophotometry, Ultraviolet; Spectroscopy, Fourier Transform Infrared; Tellurium; X-Ray Diffraction

In this study, the effect of complex formation with triethanolamine (TEA) alone and in combination with hydroxypropyl-beta-cyclodextrin (HP-beta-CD) on the photostability of ascorbic acid was evaluated for exposure to artificial and diffuse daylight. The first-order rate constants for the photodegradation reactions were determined. The data obtained showed that these complexes strongly reduced the photodegradation process with an 11- and 35-fold increase in the photostability of ascorbic acid, depending of the ligand concentration and the irradiation source. The multicomponent complex gave a significantly better stabilization for exposure to light than TEA alone. Due to the fact that the complexation extended the exposure of ascorbic acid to light (without molecular changes), UV spectrophotometric and reversed phase high performance liquid chromatographic (HPLC) methods were developed for the quantitative determination of the vitamin in pure form and in pharmaceutical preparations. These methods were statistically validated, all the validation parameters were found to be within the acceptance range. These results demonstrate that the proposed methods are suitable for the quality control of ascorbic acid, providing simple, rapid, precise, accurate and convenient approaches for routine analysis of bulk drug and pharmaceutical formulations.

Topics: 2-Hydroxypropyl-beta-cyclodextrin; Ascorbic Acid; beta-Cyclodextrins; Chromatography, High Pressure Liquid; Drug Stability; Ethanolamines; Light; Spectrophotometry, Ultraviolet

Complexation between ascorbic acid, hydroxypropyl-beta-cyclodextrin (HP-beta-CD) and triethanolamine (TEA), separately and in combination, was studied in solution and solid state. The freeze-drying method was used to prepare solid complexes, while physical mixtures being obtained by simple blending. These complexes were characterized in the solid state using differential scanning calorimetry (DSC) and infrared spectroscopy (IR). Nuclear magnetic resonance spectroscopy ((1)H and (13)C NMR) was used in aqueous solutions to obtain information about the mode of interaction. The degradation rate of each complex in solution was determined, and the stability constant of the complexes and the degradation rate of the ascorbic acid within the complexes were obtained. NMR studies provided clear evidence of partial inclusion into the HP-beta-CD cavity, but the stability constant value was very small indicating a weak host-guest interaction. The influence of complexation on the degradation rate of ascorbic acid was evaluated, and the data obtained showed a pronounced enhancement of aqueous stability with the TEA association complex, while this effect was lower with the HP-beta-CD inclusion complex. NMR experiments showed evidence of the formation of aggregates.

Topics: 2-Hydroxypropyl-beta-cyclodextrin; Ascorbic Acid; beta-Cyclodextrins; Calorimetry, Differential Scanning; Drug Interactions; Drug Stability; Ethanolamines; Freeze Drying; Magnetic Resonance Spectroscopy; Solubility; Spectroscopy, Fourier Transform Infrared