Related Experiment Video
Updated: Jul 20, 2025

Ultrafast Time-resolved Near-IR Stimulated Raman Measurements of Functional π-conjugate Systems
Published on: February 10, 2020
Low-Frequency Raman Spectroscopy: An Exceptional Tool for Exploring Metastability Driven States Induced by
Yannick Guinet1, Laurent Paccou1, Alain Hédoux1
1UMR 8207-UMET-Unité Matériaux et Transformations, Univ. Lille, CNRS, INRAE, Centrale Lille, F-59000 Lille, France.
Abstract:
The use of low-frequency Raman spectroscopy (LFRS; ω < 150 cm-1) is booming in the pharmaceutical industry. Specific processing of spectra is required to use the wealth of information contained in this spectral region. Spectra processing and the use of LFRS for analyzing phase transformations in molecular materials are detailed herein from investigations on the devitrification of ibuprofen. LFRS was used to analyze the dehydration mechanism of two hydrates (theophylline and caffeine) of the xanthine family. Two mechanisms of solid-state transformation in theophylline were determined depending on the relative humidity (RH) and temperature. At room temperature and 1% RH, dehydration is driven by the diffusion mechanism, while under high RH (>30%), kinetic laws are typical of nucleation and growth mechanism. By increasing the RH, various metastability driven crystalline forms were obtained mimicking successive intermediate states between hydrate form and anhydrous form achieved under high RH. In contrast, the dehydration kinetics of caffeine hydrate under various RH levels can be described by only one master curve corresponding to a nucleation mechanism. Various metastability driven states were achieved depending on the RH, which can be described as intermediate between forms I and II of anhydrous caffeine.
More Related Videos
10:59Label-Free Imaging of Lipid Storage Dynamics in Caenorhabditis elegans using Stimulated Raman Scattering Microscopy
Published on: May 28, 2021
12:08Rapid Antimicrobial Susceptibility Testing by Stimulated Raman Scattering Imaging of Deuterium Incorporation in a Single Bacterium
Published on: February 14, 2022
Related Concept Videos
Raman Spectroscopy: Overview
However, a small fraction of the scattered light exhibits a frequency shift due to the exchange of energy between the incident photons and...
Raman Spectroscopy Instrumentation: Overview
The monochromatic laser source, typically using visible or near-infrared radiation, generates a highly focused beam of light. This light interacts with the molecules of the sample, scattering some of the light. Liquid and gaseous samples are usually tested in ordinary glass capillaries, while solids can be analyzed as powders packed in capillaries or as potassium...
¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
¹H NMR of Labile Protons: Deuterium (²H) Substitution
IR and UV–Vis Spectroscopy of Aldehydes and Ketones
¹H NMR of Labile Protons: Temporal Resolution
The –OH proton in alcohols typically appears in the range of δ 2 to 5 ppm but can vary depending on the specific...