Effects of dose rate, absorbed dose and H₂O₂ concentration on molecular weight of alginate degraded by gamma ray Co-60 irradiation

Aqueous solutions of alginate (4%) with or without hydrogen peroxide (H2O2) were irradiated at dose ranges of 0-20 kGy by gamma Co-60 rays. Influences of the radiation scission on the molecular weight (Mw, Mn) of alginate samples were determined by gel permeation chromatography (GPC). The results showed that Mw and Mn values of alginate were significantly decreased with increasing dose. Mw and Mn of alginate reduced from 776.460 g/mol (Mw0) and 280.250 g/mol (Mn0) to 107.097 g/mol and 64.226 g/mol after irradiation at 5 kGy, and continuously decreased to 31.413 g/mol and 49.594 g/mol at dose of 20 kGy. The Mw of 9.794 g/mol (oligoalginate) was obtained with the solution irradiated at 20 kGy in the presence of H₂O₂ (2%). The influence of the dose rate on the molecular weight (Mw, Mn) of alginate irradiated at 20 kGy was also investigated. The results showed that Mw and Mn values were decreased with the decrease of dose rate. In addition, the polydispersion Index (Mw/Mn) was decreased with increasing dose as well. (author)