Flow injection–Fourier transform infrared spectrometric determination of oil and greases: preliminary microwave-assisted extraction studies

Abstract

A flow injection–Fourier transform infrared method has been developed for the determination of oil and greases previously dissolved or extracted in CCl₄. The use of the area under the FTIR absorbance spectra, from 3058 to 2780 cm^–1, corrected for a baseline established between 3200 and 2700 cm^–1, provides a sensitive and precise means for the determination of oils of different types, the only requirement being the use of standards of the same type as the samples. Using a 300 µl injection volume and a carrier flow rate of 1.5 ml min^–1, a sampling frequency of 60 h^–1 can be obtained, with a limit of detection of 1 µg ml^–1 and an RSD of the measurements between 0.5 and 4%. Preliminary results for the microwave-assisted extraction of aqueous samples with CCl₄ in a PTFE reactor provided quantitative recoveries for mineral oil, edible oil, gasoline and petroleum when an irradiation time of 6 min and an exit power of 420 W were employed.