The polymorphism of azlocillin sodium (AZ) has not been discussed suff
iciently in the literature. The results of infrared (TR)spectroscopy,
thermal analysis (combined thermogravimetry TG and differential analys
is DTA), and scanning electron microscopy (SEM) confirm that recrystal
lization of lyophilized azlocillin sodium from simple solvent acetonit
rile causes polymorphic transformation. The new polymorph obtained by
us has a crystalline form.