Raman sensitivity enhancement for aqueous protein samples using a liquid-core optical-fiber cell

Area of Science:

• Analytical Chemistry
• Spectroscopy
• Materials Science

Background:

• Raman spectroscopy is a powerful technique for molecular analysis.
• Sensitivity limitations often hinder the detection of low-concentration analytes in aqueous solutions.
• Traditional Raman cells can require larger sample volumes, posing challenges for precious samples.

Purpose of the Study:

• To develop a highly sensitive Raman spectroscopy system for aqueous solutions.
• To demonstrate the efficacy of a novel liquid core optical fiber (LCOF) Raman cell.
• To assess the detection limits and spectral quality for protein analysis.

Main Methods:

• Fabrication of a liquid core optical fiber (LCOF) Raman cell using Teflon-AF.
• Utilizing the LCOF cell for Raman spectroscopy of aqueous solutions.
• Analyzing lysozyme at a concentration of 54 microM with controlled laser power and integration time.

Main Results:

• Achieved a sensitivity enhancement factor of 500 in aqueous solutions.
• Obtained a clear spectrum of 54 microM lysozyme with a signal-to-noise ratio of 31.
• Demonstrated a shot-noise-limited spectrum, free of nonrandom noise, despite low analyte intensity relative to water background.
• Highlighted the 2.4-microL sample volume as beneficial for limited sample availability.

Conclusions:

• The Teflon-AF LCOF Raman cell significantly enhances sensitivity for aqueous samples.
• High-quality Raman spectra of proteins like lysozyme can be obtained at lower concentrations.
• The LCOF cell is suitable for analyzing trace amounts of biomolecules due to its low sample volume and high sensitivity.