Effective gamma irradiation dose on viscosity and molecular weight reduction of chitosan

Chitosan is a potential natural blood lead chelating agent. In order to improve its chelating capability, the solubility of chitosan must be enhanced. It is an essential property which is also closely related to molecular weight and viscosity. One of the most renowned and effective methods to reduce the molecular weight and viscosity of a certain particle is irradiation. This research aims to examine the effect of Gamma 60 Co irradiation upon molecular weight and viscosity of chitosan. 80 mesh chitosan was irradiated using Gamma 60 Co with different doses (0, 50, 100, and 150 kGy). This process was carried out using gamma irradiator in the Centre of Isotopes and Radiation Application at BATAN (National Nuclear Energy Agency). Viscosity and molecular weight measurements were conducted using the viscosimetric method in the chemistry laboratory of FMIPA UNNES, while molecular weight was calculated using the Mark-Houwink equation. Results showed that the specific viscosity of chitosan decreased after the irradiation process from the initial specific viscosity of 4.98 η (0 kGy dose) to 3.28 η (50 kGy), 2.87 η (100 kGy), and 2.09 η (150 kGy). A similar trend was also found in the molecular weight of chitosan from the initial molecular weight of 2.10×10 5 kDa (0 kGy dose) to 1.25×10 5 kDa (50 kGy), 1.04×10 5 kDa (100 kGy), and 5.72 × 10 4 kDa (150 kGy). It was concluded that Gamma Co 60 irradiation decreases the viscosity and molecular weight of chitosan by the effective dose of 150 kGy.