Related Experiment Video
Updated: Jun 30, 2026
11:07
Visualizing and Quantifying Pharmaceutical Compounds within Skin using Coherent Raman Scattering Imaging
Published on: November 24, 2021
Near-infrared spectroscopy for cocrystal screening. A comparative study with Raman spectroscopy
Morten Allesø1, Sitaram Velaga, Amjad Alhalaweh
1Department of Pharmaceutics and Analytical Chemistry, University of Copenhagen, Copenhagen, Denmark.
Analytical Chemistry
|September 19, 2008
Summary
Near-infrared (NIR) spectroscopy shows promise for cocrystal screening but requires reference mixtures for analysis. Raman spectroscopy offers more direct interpretation for solid-state analysis of cocrystals.
Area of Science:
- Solid-state chemistry
- Analytical chemistry
- Materials science
Background:
- Near-infrared (NIR) spectroscopy is a rapid, noninvasive technique for solid-state analysis.
- Its application in polymorph screening has been recently established.
- Cocrystal screening is crucial for developing new solid forms of active pharmaceutical ingredients.
Purpose of the Study:
- To evaluate the analytical potential of NIR spectroscopy for cocrystal screening.
- To compare NIR spectroscopy with Raman spectroscopy for cocrystal analysis.
- To investigate the formation of indomethacin cocrystals with saccharin and l-aspartic acid.
Main Methods:
- Cocrystal screening using NIR and Raman spectroscopy.
- Preparation of cocrystals via liquid-assisted cogrinding and solution crystallization.
- Analysis of spectral data using principal component analysis (PCA) for NIR spectra.
Main Results:
- NIR spectroscopy, combined with PCA, successfully identified cocrystal formation when reference mixtures were included.
- Raman spectroscopy provided direct and detailed information on cocrystal formation and polymorphic transitions.
- Liquid-assisted cogrinding and solution methods yielded a stable IND-SAC cocrystal, while l-aspartic acid resulted in a polymorphic mixture with indomethacin.
Conclusions:
- NIR spectroscopy can be applied to cocrystal screening, but its effectiveness is contingent on the availability of comprehensive reference mixtures.
- Raman spectroscopy offers a more straightforward interpretation for cocrystal analysis due to its higher spectral resolution.
- The study highlights the complementary roles of NIR and Raman spectroscopy in solid-state characterization and cocrystal development.
Related Concept Videos
01:20Raman Spectroscopy: Overview
The underlying principle of Raman spectroscopy is based on the interaction between light and matter, specifically molecules' inelastic scattering of photons. When a monochromatic beam of light, typically from a laser source, interacts with a sample, most scattered light has the same frequency as the incident light. This is known as Rayleigh scattering.
However, a small fraction of the scattered light exhibits a frequency shift due to the exchange of energy between the incident photons and the...
However, a small fraction of the scattered light exhibits a frequency shift due to the exchange of energy between the incident photons and the...
01:26Raman Spectroscopy Instrumentation: Overview
A conventional Raman spectrophotometer includes a laser source, a sample holding system, a wavelength selector, and a detector.
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...
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...
01:24IR Spectroscopy: Molecular Vibration Overview
When Infrared (IR) radiation passes through a covalently bonded molecule, the bonds transition from lower to higher vibrational levels. The fundamental vibrational motions that result in infrared absorption can be classified as stretching or bending vibrations.
Stretching vibrations are vibrational motions that occur along the bond line, changing the bond length or distance between two bonded atoms. They are further distinguished as symmetric or asymmetric. In symmetric stretching, the...
Stretching vibrations are vibrational motions that occur along the bond line, changing the bond length or distance between two bonded atoms. They are further distinguished as symmetric or asymmetric. In symmetric stretching, the...
01:28IR and UV–Vis Spectroscopy of Carboxylic Acids
In IR spectroscopy of carboxylic acids, the C=O bond shows a characteristic band between 1710 and 1760 cm⁻¹, and the O–H bond exhibits a broad band between 2500 and 3300 cm⁻¹.
However, the stretching absorptions for the C=O bond vary depending on the structure of carboxylic acids. The C=O bond of the free carboxylic acids shows a higher stretching frequency, 1760 cm−1, while H-bonded carboxylic acids (dimers) exhibit stretching absorptions at a lower frequency, 1710 cm−1. The C=O bond of the...
However, the stretching absorptions for the C=O bond vary depending on the structure of carboxylic acids. The C=O bond of the free carboxylic acids shows a higher stretching frequency, 1760 cm−1, while H-bonded carboxylic acids (dimers) exhibit stretching absorptions at a lower frequency, 1710 cm−1. The C=O bond of the...
01:16IR Spectroscopy: Hooke's Law Approximation of Molecular Vibration
A covalently bonded heteronuclear diatomic molecule can be modeled as two vibrating masses connected by a spring. The vibrational frequency of the bond can be expressed using an equation derived from Hooke's law, which describes how the force applied to stretch or compress a spring is proportional to the displacement of the spring. In this case, the atoms behave like masses, and the bond acts like a spring.
According to Hooke's law, the vibrational frequency is directly proportional to the...
According to Hooke's law, the vibrational frequency is directly proportional to the...
01:11Applications of IR Spectroscopy: Overview
The non-destructive nature and ability to provide valuable chemical information make IR spectroscopy a versatile technique with broad applications in various scientific and industrial fields. IR spectroscopy is commonly used to identify and characterize organic and inorganic compounds. It provides information about the functional groups present in a molecule and the bonding between atoms. This helps in the structural elucidation of compounds during organic synthesis, pharmaceutical research,...