RESUMEN
The ratio of mechanical and radical effects for the ultrasonic degradation of dextranes in aqueous solutions was studied in dependence of frequency and molecular weight of the dextranes. For low ultrasound frequency (35 kHz) a stronger increase of the polymer degradation with increasing molecular weight was found as expected on the basis of the radicals present. This is due to the mechanical effects of ultrasound. Applying higher frequencies (>500 kHz) only radical reactions are responsible for the degradation. Below a molecular weight limit of 40000 the mechanical effects vanish.
Asunto(s)
Educación en Salud/métodos , Promoción de la Salud/métodos , Rol del Médico , Rol , Alemania Oriental , HumanosRESUMEN
The degradation products formed in aerated aqueous alpha-D-glucose solutions by cleavage of the carbon skeleton by ultrasound and gamma irradiation are compared. Common products present for both types of irradiation are: D-glyceraldehyde, D-glyceric acid, hydroxy-malondialdehyde, 2,3-dihydroxy-4-oxo-butanoic acid, tetrodialdose, D-arabinoic acid and D-xylose. 2,3,4-Trihydroxy-5-oxo-pentoic acid and D-arabinose could be detected only by radiolysis and evidence for the formation of 2-hydroxy-3-oxo-pentoic acid was only obtained in sonolysis. These fragmentation products are supposed to be formed by reactions of the glucose-peroxyl radicals with HO2-radicals. Based on the reactions of peroxyl radicals given in the literature, a mechanism is proposed which leads to the observed products.
Asunto(s)
Rayos gamma , Glucosa/efectos de la radiación , Radiación Ionizante , Ultrasonido , Fenómenos Químicos , Química , Glucosa/análisis , SolucionesRESUMEN
The oxidation products obtained in aerated, aqueous alpha-D-glucose solutions after irradiation with ultrasonic waves and gamma-rays were compared. Separation and identification were performed by gas chromatography/mass spectrometry and three methods for the derivatization of the products were used: (1) trimethylsilylation of the OH groups; (2) methoximation of the carbonyl groups followed by trimethylsilylation of the OH groups; (3) reduction of the carbonyl and carboxyl groups to alcohols by sodium borodeuteride, followed by trimethylsilylation of the OH groups. When using ultrasound and gamma-irradiation identical products were observed: D-glucono-1,4-lactone, D-glucono-1,5-lactone, D-arabino-hexos-2-ulose, D-ribo-hexos-3-ulose, D-xylo-hexos-4-ulose, D-xylo-hexos-5-ulose, D-glucohexodialdose and arabino-1,4-lactone. From the results it was concluded that in ultrasound and gamma-irradiation the same primary species and consecutive reactions are involved in product formation.