Dielectric polarisation in folic acid: role of bound water molecules

The frequency and temperature dependence of dielectric constant and dielectric loss in the case of a vitamin, Folic acid, is studied in the range 10 kHz to 1 MHz and 275 K to 353 K. It is observed that both the dielectric constant and loss decrease initially very rapidly with frequency and appear to saturate at higher frequencies in accordance with space charge polarisation. A peak around the temperature of 313 K has marked the temperature dependence. The observed results may be attributed to bound water molecules present in the vitamin matrix. As the thermal energy is supplied some of the water molecules undergo transition from bound to free state and contribute to polarisation. Above the temperature of 313 K a diffusion process enhanced by elevated temperature becomes the dominant one and the number of water molecules contributing to polarisation decreases thereby decreasing the dielectric constant. As no relaxation phenomena has been observed the observed behaviour of dielectric loss is similarly explained.