Estimation of the two sample preparation techniques for infrared spectroscopic identification of Cefamandole nafate in solid state

The European Pharmacopoeia (Ph.Eur.) monograph for Cefamandole Nafate (CFN) and the revised monograph prescribe the identification of the antibiotic in solid state by infrared (IR) absorption spectrophotometry using potassium bromide (KBr) disc technique. But, this technique may cause unwanted solid-solid transformations in the crystalline structure of the beta-lactam antibiotic CFN. The latter is a drug with proven polymorphism/pseudopolymorphism. In this context we have examined the suitability of the two techniques (KBr disc and Nujol mull) for IR spectral analyses to identify the antibiotic CFN in solid state. The results of our examinations show that KBr disc technique alters the crystalline state of CFN during the preparation of its KBr disc samples by the tribomechanical treatments (grinding and compression pressure). On the contrary, the Nujol mull technique does not cause such transformations and it is estimated as a better, more suitable technique to be employed for identification of CFN. For a greater precision, in solving the possible difficulties due to the KBr disc technique a second record of IR spectra is necessary to be provided by the Nujol mull technique with use of an internal standard (the stretching vibration of vC = 0 of the condensed beta-lactam cycle).