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Updated: Jun 18, 2026

Resolving Water, Proteins, and Lipids from In Vivo Confocal Raman Spectra of Stratum Corneum through a Chemometric Approach

Resolving Water, Proteins, and Lipids from In Vivo Confocal Raman Spectra of Stratum Corneum through a Chemometric Approach

Published on: September 26, 2019

On optical depth profiling using confocal Raman spectroscopy.

N A Freebody¹, A S Vaughan, A M Macdonald

¹School of Electronics and Computer Science, University of Southampton, Highfield, Southampton SO17 1BJ, UK.

Analytical and Bioanalytical Chemistry

|November 17, 2009

Summary

This summary is machine-generated.

Confocal Raman spectroscopy depth profiling is better explained by photon scattering from an extended illuminated volume, not ray optics. Surface flatness is crucial for accurate depth profiling in materials, more so than refractive index matching.

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Area of Science:

Analytical Chemistry
Materials Science
Spectroscopy

Background:

Confocal Raman spectroscopy depth profiling was historically modeled using geometrical optics, leading to inaccuracies in understanding material profiles.
Previous attempts to refine Raman spectroscopy techniques failed to fully explain observed depth profiles and spectral characteristics.

Purpose of the Study:

To provide evidence for a photon scattering model over a ray optics approach for confocal Raman spectroscopy.
To develop a numerical model that accurately explains depth profiling in transparent and semicrystalline materials.

Main Methods:

Developed a numerical model incorporating surface refraction, bulk scattering attenuation, Raman scattering efficiency, and surface roughness.
Investigated the influence of surface flatness and refractive index matching on depth profiling accuracy.

Main Results:

The photon scattering model successfully explains depth profiling, including spectra from laminated samples and measurements above the focal point.
Surface roughness and flatness significantly impact depth profile accuracy, often more than refractive index matching with immersion oil.
Oil immersion objectives do not guarantee sampling only at the focal point due to scattering effects.

Conclusions:

A photon scattering model provides a more accurate understanding of confocal Raman spectroscopy depth profiling than traditional geometrical optics.
Surface preparation, specifically achieving flatness, is critical for high-quality Raman depth profiling of transparent and semicrystalline materials.
The findings challenge conventional assumptions about sample preparation requirements for Raman spectroscopy.