Application of spectral-focusing-CARS microscopy to pharmaceutical sample analysis

J G Porquez,A D Slepkov

doi:10.1063/1.5027273

Abstract

We implement spectral-focusing-CARS hyperspectroscopy to characterize pharmaceutical samples. The use of a dynamically-power-tuned supercontinuum seeding method combined with epi-detection of the CARS signals allows for broadband hyperspectroscopy and rapid single vibrational frequency imaging with microsecond pixel dwell times. The broad hyperspectral capabilities spanning about 3000 cm-1 of vibrational information allow for facile discrimination between ibuprofen, common polymorphs of acetaminophen, and starchy binders. Application of 3-D hyperspectral imaging on bare tablet forms reveals surface-bound processing of low-dose drugs such as cetirizine.

Highlights

Coherent anti-Stokes Raman scattering (CARS) is a non-linear optical process involving the generation of anti-Stokes photons by frequency mixing of laser light—the pump, probe and Stokes— in a non-linear material
A mixture of acetaminophen and ibuprofen along with their excipients are indistinguishable when observed under normal light illumination, with vibrational contrast, CARS imaging based on characteristic peak signatures from these pharmaceutical drugs can help discriminate between drug components
Spectral-focusing CARS microscopy using a spectrally-surfed photonic crystal fiber (PCF) supercontinuum Stokes has been applied to chemical mapping and 3-D imaging of pharmaceutical drug tablets

Summary

Introduction

Coherent anti-Stokes Raman scattering (CARS) is a non-linear optical process involving the generation of anti-Stokes photons by frequency mixing of laser light—the pump, probe and Stokes— in a non-linear material. Application of spectral-focusing-CARS microscopy to pharmaceutical sample analysis

Results

Conclusion