Synthesis of low molecular weight chitosan using hydrogen peroxide and gamma rays irradiation

Our previous researches shown that the low molecular weight chitosan had better effectiveness as plant growth promoter than the high molecular weight chitosan. We obtained the low molecular weight chitosan through the polymer degradation using gamma rays irradiation within irradiation dose of 70-100 kGy. However, this lab scale process could not be implemented for manufacturer scale due to its consuming irradiation time and thus causing high production cost. To solve this problem, we introduce one degradation process i.e., using hydrogen peroxide; as so it can reduce the irradiation dose. The parameters used in this research are hydrogen peroxide concentration from 0 to 2 M, immersing time of chitosan with hydrogen peroxide from 0 to 6 hours and chitosan irradiation dose from 0 to 30 kGy. The measurement analysis included viscosity measurement, FTIR spectrophotometry and molecular weight determination via the intrinsic viscosity method. The results of viscosity measurement on the low molecular weight chitosan showed decreasing trend with the increasing of hydrogen peroxide concentration and immersing time of chitosan with the hydrogen peroxide. The optimum hydrogen peroxide concentration and immersing time of chitosan are 2 M and 3 hours; respectively. The molecular weight determination of the low molecular weight chitosan also showed decreasing trend with the increasing irradiation dose; reached to 200 kDa at irradiation dose of 30 kGy. These results imply that the use of hydrogen peroxide is effective for the process of chitosan degradation as to obtain the expected low molecular weight. (author)