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

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.