If the best crystalline form of a drug is not well evaluated and selected for development, crystalline changes may occur in the late clinical stage, resulting in huge economic losses due to delayed marketing of the drug, and even more serious losses if the drug is forced to be withdrawn from the market due to crystalline changes after marketing. The bond lengths and bond angles of certain chemical bonds in different crystalline drug molecules will be different, resulting in different vibrational-rotational jump energy levels, and some main features of their corresponding infrared spectra, such as absorption band frequencies, peak shapes, peak positions and peak intensities, will also be different, so infrared spectroscopy can be used for the study of drug polymorphs. Commonly used sample preparation methods for IR spectroscopy include KBr compression, paraffin paste, diffuse reflection and attenuated total reflection (ATR). Considering that grinding may lead to the change of drug crystalline shape, paraffin oil paste method or diffuse reflection infrared Fourier variation spectroscopy (DRIFT) is mostly used for the determination of drug crystalline shape by infrared spectroscopy.
Fig.1 NIR spectra of calibration samples used for calibration model development. (A) Raw average spectra, (B) SNV and 1st derivative pretreated spectra. (Liew, 2010)
Infrared spectroscopy is simple and fast, however, for some drugs with different crystalline forms and the same or little difference in infrared spectra, it is difficult to distinguish the infrared spectra, and sometimes the difference in the spectra may be due to the lack of sample purity, the size of the crystals, the transfer of crystals in the grinding process, etc., resulting in deviations in the analytical results. This is when other methods are needed to jointly determine the crystalline form of the sample at the same time. Our skilled scientists at CD Formulation use state-of-the-art infrared (IR), near infrared (NIR) and Raman spectrometers for solid state analysis. These techniques provide methods for qualitative characterization of different solid forms and for quantifying the composition of solid forms in a drug substance or product.
CD Formulation can provide infrared spectroscopy services for a wide range of drugs in our compliant laboratory equipped with state-of-the-art analytical instrumentation. Our scientists provide proven analytical process development and validation services and work as an integrated team to provide solutions that make your project a success.
If you have a requirement about our services, please contact us by phone or email, our colleagues will reply to you within three working days.