Determination of the water content in petroleum products using terahertz transmission spectroscopy

The water content in polyglycol oils is investigated by Terahertz Time-Domain Spectroscopy (THz-TDS). These oils are able to dissolve a certain percentage of water. Changes in the absorption coefficient and refractive index are observed related to the amount of water added to the pure oils. Comparison of the experimental data with predictions based on Beer-Lambert and Lorentz-Lorenz-theory, respectively, exhibits an excellent agreement. Analyses with Fourier Transform Infrared (FTIR) Spectroscopy reveal sensitivity similar to the THz-TDS experiment. THz- TDS may offer powerful tools to quantitatively determine the water concentration in petroleum products.