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This proof of concept study demonstrates the application of transmission Raman spectroscopy (TRS) to the non-invasive and non-destructive quantification of low levels (0.62-1.32% w/w) of an active pharmaceutical ingredient's polymorphic forms in a pharmaceutical formulation. Partial least squares calibration models were validated with independent validation samples resulting in prediction RMSEP values of 0.03-0.05% w/w and a limit of detection of 0.1-0.2% w/w. The study further demonstrates the ability of TRS to quantify all tablet constituents in one single measurement. By analysis of degraded stability samples, sole transformation between polymorphic forms was observed while excipient levels remained constant. Additionally, a beam enhancer device was used to enhance laser coupling to the sample, which allowed comparable prediction performance at 60 times faster rates (0.2s) than in standard mode.

Original publication





Journal of pharmaceutical and biomedical analysis

Publication Date





35 - 45


Cobalt Light Systems Ltd., Milton Park, Abingdon, OX14 4SD, UK. Electronic address:


Pharmaceutical Preparations, Dosage Forms, Calibration, Spectrum Analysis, Raman, Least-Squares Analysis, Chemistry, Pharmaceutical, Models, Theoretical, Limit of Detection