Vibrational imaging of tablets by epi-detected stimulated Raman scattering microscopy

Abstract

Proper chemical imaging tools are critical to the pharmaceutical industry due to growing regulatory demand for intermediate and end-product content uniformity testing. Herein we demonstrate stimulated Raman scattering (SRS) imaging of active pharmaceutical ingredient (API) and four excipients within tablets. Tablets from six manufactures were imaged with a speed of 53 s per frame of 512 × 512 pixels (i.e., 200 μs per pixel) and a lateral spatial resolution as high as 0.62 μm. The SRS chemical imaging was compared to confocal Raman mapping and coherent anti-Stokes Raman scattering (CARS) chemical imaging in terms of speed and chemical selectivity. The acquisition speed of SRS imaging is ca. 10⁴ times faster than confocal Raman mapping and SRS technique showed superior to CARS chemical selectivity for studied samples. Our data demonstrate the potential of SRS microscopy in high-speed screening of pharmaceutical solid dosage forms.