Physico-chemical characterisation of a new polymorph of caffeine

Caffeine is a widely used drug substance. Two polymorphic forms and one hydrate of caffeine are known. Thanks to scanning transitiometry, the curves pressure versus temperature, P = f(T), of the caffeine were plotted. A (temperature, pressure) unary phase diagram was deduced. It confirms the existence of a new polymorph of caffeine at low pressure synthesized by sublimation. Its identification and its physico-chemical properties were determined using a variety of experimental methods: X-ray powder diffraction, differential scanning calorimeter, thermogravimetric analysis, thermally stimulated current and electrochemical impedance.