Broadband Determination of Biodiesel Content in Petroleum Diesel Blends by Terahertz Time Domain Spectroscopy

The biodiesel content in petroleum diesel-biodiesel blends is determined using broadband terahertz time-domain spectroscopy. We model the spectra of the blend components based on the nonpolar characteristics of the samples. The biodiesel content in diesel is determined from the coefficients that best fit the measured spectra to the optimal linear combination of the model for each individual component (pure diesel and pure biodiesel). This method proves to be valid for real-time applications. A simpler approach based on the maximum observed dispersion is also demonstrated to be a distinctive characteristic of a given blend.