A Vertical Flow Method for Sensitive Raman Protein Measurement in Aqueous Solutions

Area of Science:

• Analytical Chemistry
• Spectroscopy
• Optics

Background:

• Raman scattering is inherently weak, limiting the sensitivity of Raman spectroscopy.
• Improving signal detection efficiency is crucial for broader applications of Raman spectroscopy.
• Existing methods for enhancing Raman signals can be complex or require specialized materials.

Purpose of the Study:

• To develop a simple and effective method for enhancing Raman signal detection efficiency.
• To introduce the vertical flow method as a derivative of liquid core optical fiber techniques.
• To demonstrate significant signal enhancement and improved limit of detection in Raman spectroscopy.

Main Methods:

• The vertical flow method involves flowing sample solution from a pinhole to create an air-wrapped liquid column.
• Total internal reflection at the sample-air interface confines the excitation beam and Raman signal.
• The confined Raman signal is efficiently collected as it emerges from the pinhole.

Main Results:

• Achieved Raman signal enhancement of up to 90 times compared to conventional methods.
• Demonstrated a low limit of detection (LOD) of 0.029 ± 0.003 mg mL⁻¹ for bovine serum albumin.
• Analyzed the dependence of signal enhancement on various parameters within the vertical flow method.

Conclusions:

• The vertical flow method offers a simple yet powerful approach to enhance Raman spectroscopy sensitivity.
• This technique utilizes readily available materials, making it broadly accessible.
• The method shows significant potential for sensitive detection in various analytical applications.