High Sensitivity Detection of Liquids in Gasoline Admixtures with THz Time-Domain Spectrometers

This paper presents low detection limit (ppm level) measurements of admixtures dissolved in gasoline liquid samples using Terahertz Time-Domain Spectroscopy (THz-TDS). Contrary to the methods which are based on spectroscopic measurements we found that the pulse delay is an adequate parameter to detect water or alcohol admixtures in gasoline. The method is validated for water and isopropanol admixtures in gasoline with a precision of down to 250 ppm in case of water.