Recent advances in low-frequency Raman spectroscopy for pharmaceutical applications.

Low-frequency Raman (LFR) spectroscopy probes vibrational modes related to long-range order (i.e., crystallinity) that can provide unique information on the solid-state/structural characteristics among other properties. Furthermore, the recent advancements in instrumentation (most notably, narrow wavelength band filters) and data analysis has allowed to overcome some of the previous limitations of this technique. In fact, LFR spectroscopy has now enjoyed a surge in popularity with applications found in many research areas. This mini-review article provides a comprehensive summary of established and exciting new LFR applications for pharmaceutical analysis. Aspects of the underlying theory, instrumentation and data analysis (including application of chemometric and computational techniques) are also discussed in detail.