Relationship between dehydration energy and particle size reduction energy during dehydration of Beclomethasone Dipropinate and Norfloxacin

Abstract

Dehydration of beclomethasone propionate monohydrate (BDM) with isothermal differential scanning calorimetry (IDSC) was performed and the particle size of BDM was markedly decreased from 328 to a range of 30 to 60 micron. At the temperatures of 65, 60 and 55 0 C, the apparent particle size reduction energy of 17.83 to 29.23 J/g was appropriate. This range of energy, however, was not suitable to reduce the particle size at 70 0 C which needed up to 48.57 j/g. IDSC of BDM showed similar dehydration energy at 55, 60, 65 and 70 0 C. thus, the energy consumption for complete dehydration was independent of the temperature range used. Crystalline water of BDM was linearly decreased with dehydration time whereas at 70 0 C. the dehydration pattern showed initial delay in water loss and immediately followed by rapid dehydration. Dehydration energy and particle size determination revealed that the particle size of BDM was reduced to minimum while crystalline water was still present. Thus, more energy was needed to completely remove the remaining water from their crystal lattice. The initial stage of isothermal dehydration affected the final particle size of BDM while the later stage dealt with the solid state transformation of remaining BDM to BD without any change in particle size. The hydrogen bonds of BDM found to be a weak type hydrogen bond and the low value of the coefficients of packing (Kchan) supported an ease of size reduction during isothermal dehydration. four stoichiometric norfloxacin (NF) hydrates (dihydrate, hemipentahydrate, trihydrate, pentahydrate) and one disordered NF state, were generated by various methods and characterized. X-ray powder diffraction (XRPD) patterns of all NF hydrates exhibited crystalline structures. NF hydrates transformed to anhydrous NG from A after gentle heating at 60 0 C for 48 hours except dihydrate and trihydrate where mixture in XRPD patterns between anhydrous NF from a and former structures existed. Desiccation of NF hydrates at 0% RH for 7 days resulted in only partial removal of water molecules from the hydrated structures. The hydrated transitional phase and the disordered NF state were obtained from the incomplete dehydration of NF Hydrates after thermal treatment and desiccation of penthydrate NF, respectively. Anhydrous NF from a and NF hydrates transformed to pentahydrate NF when exposed to high moisture environment except dihydrate. in conclusion, surrounding moisture levels, temperatures and the duration of exposure strongly influenced the interconversion pathways and stoichiometry of anhydrous NF and its hydrates. unlike BDM, NF hydrates did not show significant particle size reduction after dehydration due to the very compact structures and by high Kchan value obtained for dihydrate NF. Thus, NF hydrates were physically very stable and less likely to collapse after dehydration. Dehydration energy of lower stoichiometric hydrate (hemipentahydrate NF) was lower than higher hydrates (trihydrate NF and pentahydrate NF) due to the number, position and strength of hydrogen bonding between crystalline water and NF moiety in crystal lattice structure. The total dehydration energy for every NF hydrates were temperature independent and found to be much higher than the value obtained for BDM despite the calculation methods used.