Assembly and characterization of an optical fiber probe for use in a portable Raman spectrometer

This study describes the assembly and testing of an optical fiber Raman probe for use in a portable spectrometer using a 785 nm laser. The Raman probe was tested on edible vegetable oils (extra virgin olive, canola, sunflower, corn, and soybean), with the distal end of the probe immersed in each sample. The spectra of a dipyrone tablet and a mothball were also obtained. The silica peaks were subtracted by taking a spectrum with the probe tip immersed in water. The spectra of the samples exhibited characteristic peaks from vibrations of unsaturated fatty acids between 900 and 1800 cm⁻¹, as well as characteristic peaks of silica from 600 to 1200 cm⁻¹. The spectra of the samples after subtraction of the silica spectrum (probe in water) showed characteristic peaks without alterations in position or relative intensities compared without the probe. Exploratory analysis by principal component analysis was able to identify peaks of the constituent fatty acids in the oils and associate them with the oil type. A classification model based on partial least squares regression allowed for the classification of oil spectra with an accuracy of 77%. This study demonstrated the feasibility of coupling a probe to a portable Raman spectrometer with the goal of monitoring and controlling industrial processes.