This paper demonstrated the quantitative detection of ethanol and acetone mixtures in complex solutions with Raman spectroscopy based on headspace gas analysis. By analyzing the volatile components in the headspace, their concentrations in liquid solutions were determined. We constructed our own Raman spectroscopy system to detect the headspace gas quantitatively over a solution in a sealed vial. The Raman spectra of the headspace gases over standard solutions were standardized for finding the concentrations of ethanol, acetone, and ethanol–acetone in mixture solutions. The results showed that the concentration of a gaseous component in the headspace gas was proportional to its ratio in the liquid solution. We obtained a linear relationship between the spectral intensity of volatile components in headspace and the concentration of the liquid solutions. Then, we analyzed the alcohol concentration in a white wine and a Chinese liquor called Fen Chiew by measuring the Raman spectra of the headspace gas over their liquids. For the river water sample, we also implemented our headspace gas detection with Raman spectra to obtain the concentration of acetone in the river sample. This work demonstrated the facilitation of headspace gas analysis by the qualitative and quantitative determination of volatile substances from liquid samples using Raman spectroscopy.
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