CO2, laser infrared optothermal spectroscopy for quantitative adulteration studies in binary mixtures of extra-virgin olive oil

Optothermal window spectroscopy at CO2 laser infrared wavelengths was used to detect the extent of adulteration of extra-virgin olive oil by sunflower and safflower oils. A good linearity between the strength of optothermal signal and the concentration of each adulterating compound was found. Predicted limits of detection presently attainable by this new method are 6 (w/w) and 4.5% (w/w) for extra-virgin olive oil adulterated with safflower oil and sunflower oil, respectively, and were confirmed experimentally; the corresponding relative errors were 0.3 and 0.18%. Interference effects are comparable to those encountered in other spectroscopic methods at the same wavelength.