Raman Spectroscopy applied to polymorphism of Tamoxifene Citrate

Different strategies for a systematic study of polymorphism can be applied: XRPD, DSC, FT-IR and Raman spectroscopy. Unlike X-ray diffraction Raman microscopy, a non-destructive and non-invasive technique, can be applied to pure solids or dosage forms without any sample preparation. The ability of Raman spectroscopy to discriminate between polymorphs has been demonstrated: different crystal structures usually show intensity and frequenciey changes in the Raman spectrum particularly in the rather crowded area from ~ 500 to ~ 1700 cm-1, known as “fingerprint region” which contains the majority of the bands used to identify a particular material. The use of Raman microscopy has been demonstrated for Tamoxifen Citrate: its trans isomer is in fact well known for its endocrine activity as an antiestrogenic agent. Tamoxifen citrate exists in two polymorphic form A and B, Which were found to have a distinct micro Raman spectrum whith bands attributable to the different forms. Another possible form was found and its Raman spectrum is different from the others. Other methods for the characterization of the three forms were used: XRDP, DSC, ATR/FTIR. Because of its non-invasive character, by focusing the micro Raman laser in to a capillary tube the convertion at room temperature of a suspension in ethanol of form A to B has been observed. Finally, the sensitivity to polymorphism of Raman spectroscopy, which makes it an ideal candidate for studies of crystal forms of Pharmaceutical compounds, could be analysed.