To develop a non-invasive method for quantifying methanol in unopened spirit bottles using Raman spectroscopy.
Approach:
Method Development: The researchers combined wavefront shaping with wavelength modulation to read the chemical signature of liquids through the bottle.
Excitation Light Shaping: A conical beam was used to focus inside the liquid, minimizing interference from the glass.
Fluorescence Suppression: Wavelength modulation was applied to shift the excitation wavelength, allowing for the isolation of Raman peaks from the fluorescence background.
Data Analysis: Principal component analysis was employed to extract Raman features from the modulated spectra.
Key Findings:
The method improved the signal-to-noise ratio of through-bottle Raman measurements by up to 12-fold.
Wavelength modulation consistently enhanced performance across various commercial spirits.
The method was sensitive enough to detect methanol levels below the maximum tolerable concentration.
Interpretation:
Limitations:
Highly scattering containers, such as frosted glass, distorted the excitation beam and posed challenges for detection.
