Characterization and quantification of amorphous content in some selected parenteral cephalosporins by calorimetric method

Abstract

Amorphous content of a crystalline drug affects its physical and chemical properties as well as its performance. Consequently it is important to assess the extent of amorphous contents in pharmaceuticals. The present study utilizes the technique of solution calorimetry to quantify the percentage of crystallinity in samples of varying amorphous content in cefazolin sodium monohydrate, ceftriaxone sodium, cefotaxime sodium and cefoperazone sodium. Enthalpy of solution of 100% crystalline and amorphous drugs as well as their physical mixtures over the range 0-100 mass/mass% amorphous content were determined. As expected it has been found that amorphous forms have significantly higher energy than the corresponding crystalline form for all the drugs. Enthalpy of solution (ΔsolH), an extensive thermodynamic property can provide a precise and unambiguous measure of the relative crystallinity provided amorphous and crystalline standards are appropriately chosen. A good correlation has been found between ?solH and the amorphous contents of the drugs.