Utilization of Fourier transform-Raman spectroscopy for the study of pharmaceutical crystal forms

It is well understood that the solid state physical characterization of a drug substance is necessary for successful development and approval of a pharmaceutical product AAPS [1]. Physical analytical techniques used include: XRD, IR, DSC, TG, and NMR. Recently, Fourier transform (FT) Raman spectroscopy has become a more common technique. Complimentary to IR, FT-Raman can be used to differentiate between different crystal forms of a drug substance. FT-Raman exhibits several advantages over IR and the other physical analytical techniques. Very little sample is required with no preparation (dilution), analysis time is quick, and since water is a weak scatter (Raman spectrum of water contains three low intensity peaks), crystallization studies of drug substances from aqueous solutions can be performed. Additionally, through the use of a variable-temperature accessory, phase diagrams can be determined for crystal systems, leading to further characterization of those systems. This paper introduces the use of FT-Raman spectroscopy for pharmaceutical development activities. Specific examples will be shown for investigations of crystal forms (qualitative and quantitative) and crystallization studies.

Quantitation of cefepime.2HCl dihydrate in cefepime.2HCl monohydrate by diffuse reflectance IR and powder X-ray diffraction techniques

The identification, characterization and quantitation of crystal forms is becoming increasingly important within the pharmaceutical industry. Multi-disciplinary, physical analytical techniques are necessary for this task. In this work, diffuse reflectance mid-infrared (IR) and powder X-ray diffraction (XRD) analyses were used to identify two different hydrated forms of cefepime.2HCl, a cephalosporin. Characterization of the mono- and dihydrate forms led to separate IR and XRD quantitative assays for the determination of dihydrate content in cefepime.2HCl monohydrate bulk material. For the IR assay, a working range of 1.0-8% (w/w) was established with a minimum quantifiable level (MQL) of 1.0% (w/w) and a limit of detection (LD) of 0.3% (w/w) dihydrate in monohydrate material. The XRD assay displayed a working range of 2.5-15% (w/w) with an MQL of 2.5% (w/w) and an LD of 0.75% (w/w). Cross validation was performed between the two techniques, with a good correlation displayed for each assay as compared with the known concentrations and as compared with each other. In addition, a full evaluation of potential assay errors was made.