States of water adsorbed on perindopril crystals

The relationship between the structural state of adsorbed water, the crystal structure of the substances, and the solubility of the perindopril salt C₁₉H₃₂N₂O₅ · C₄H₁₁N in water was studied by IR spectroscopy and X-ray diffractometry. The high-frequency shift of the stretching vibrations of adsorbed water and the solubility depend on the crystal structure of the drug substance. A reversible chemical reaction occurred between the adsorbed water and the perindopril salt.