Attenuated Total Reflection (ATR) spectroscopic imaging has been employed to great effect to study the compaction and dissolution of pharmaceutical formulations. It has many advantageous capabilities suited for the study of pharmaceutical formulations compared to other imaging approaches, due to the high levels of chemical and spatial specificity that can be achieved along with relatively fast acquisition times. It is now becoming a very important tool in the development and testing of oral dosage formulations.
Working in the mid-infrared region is particularly useful when studying pharmaceuticals, as in this frequency range, especially in the fingerprint region; it is comparatively simple to distinguish the individual components. This region of the spectrum also provides a great deal of information concerning the crystalline state of a compound, any intermolecular interactions that might be present and the occurrence of any polymorphic transitions.
The focal place array (FPA) detector employed in FTIR imaging facilitates the gathering of both spectral and spatial information about a sample simultaneously. The capability of determining the locations and molecular states of the various components of a sample is very important as these properties have a direct effect on the efficacy of a tablet in the body. ATR-FTIR spectroscopic imaging can be performed in both micro and macro modes. Micro ATR-FTIR imaging provides a high spatial resolution (e.g. see Anal Chem 2003). Macro ATR-FTIR imaging without the use of an IR microscope facilitates the imaging of greater fields of view and opens a range of possibilities for studying large areas or whole tablets e.g. see Macromolecules 2003).
ATR in macro mode is suited to the study of oral dosage formulations as little sample preparation is required and due to the small depth of penetration of the radiation into the medium it is feasible to work with aqueous samples. The rapid acquisition time means that study of dynamic systems is possible, hence facilitating studies of the dissolution of pharmaceutical tablets in-situ, producing time resolved images of the dissolution of the polymer and drugs in the sample. (see our review article Applications of Fourier transform infrared spectroscopic imaging to tablet dissolution and drug release Expert Option on Drug Delivery (2013) 10(9),1207-1221 (doi).
We collaborate with major pharmaceutrical companies in this area, such as Pfizer, GlaxoSmithKline, Bristol Myers Squibb, Abbott, AbbVie, Merck Sharp & Dohme, Daiichi-Sankyo and other companies (see our Industrial Outreach section and corresponding joint articles with these companies). Our most recent article entitled "Recent advances in the applications of vibrational spectroscopic imaging and mapping to pharmaceutical formulations" Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2018) (doi) which reviews recent developments in this field.
More information with ket references can be found in these pages: