Development of a detection method based on dielectric spectroscopy for real-time monitoring of meta-cresol contamination in beach-sand

A microwave-based, rapid and non-destructive spectroscopic technique has been developed to monitor contamination in beach-sand. A set of in-vitro experiments were designed to test beach-sand samples contaminated with meta-cresol (m-cresol) and water with weight/weight percentages of 0–20%, using a prototype probe with a long sample holder (16   mm). The frequency range used was 10   MHz–1   GHz during the whole experiment. Air and Teflon were investigated as low-loss materials, whilst ethanol was used as a typical, frequency-dependent, polar material to further verify the technique. The real part of the relative complex permittivity was found to be very close to the theoretical and fitting very well with the Debye model. This dielectric technique showed a linear relationship between the real part of relative complex permittivity and m-cresol/water content, for a frequency range of 0.02–0.7   GHz for water and 0.02–0.2   GHz for m-cresol. The sensitivity was calculated to be 0.58% −1 and 0.12% −1 for water and m-cresol, respectively.