The effect of gamma rays upon L-proline and 4-hydroxy-L-proline. A thermochemical study

The differential scanning calorimetric (DSC)-thermogravimetry (TG) techniques have been employed in order to investigate the thermal behavior of two amino acids, namely: L-proline and 4-hydroxy-L-proline gamma irradiated. The results were compared with similar ones for the same non-irradiated compounds. The samples were irradiated at room temperature with gamma radiations using a Cs-137 source. The exposure doses ranged between 0.63 kGy- 10 kGy. The phase transition points (melting) and decomposition processes occurring by heating were put in evidence from DSC thermograms in the temperature range between ambient to 500 degrees C. The effects of gamma rays on thermal parameters and their variation as a function of dose were analyzed. The measurements have shown that after L-proline and 4-hydroxy-L-proline irradiation, the values of the melting/decomposition temperatures, enthalpies, heat capacities, weight loss and purity decrease. The GC-MS technique was used to identify the yields of the molecular products of the irradiation, and Fourier transformed infrared (FTIR) method to highlight the functional groups and hydrogen bonds and their modification related to irradiation.