Comparison of the crystallinity of imipenem samples by X-ray diffraction of amorphous material

The intensity of X-rays diffracted by amorphous material in samples of the beta-lactam antibiotic imipenem [(5R,6S)-3-[[2-(formimidoyl-amino)ethyl]thio]-6-[(R)-1- hydroxyethyl]-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylic acid] was used to compare the crystallinity of the samples. The method makes use of the intensity in the X-ray powder diffraction (XRPD) pattern at a diffraction angle of 28 degrees (2 theta), at which no crystalline peaks are observed. A linear relationship (R2 = 0.9999) exists between amorphous intensity and crystallinity for synthetic mixtures of amorphous and crystalline imipenem. Sample preparation techniques ordinarily used in XRPD experiments were utilized.