Highly sensitive characterization of glucose aqueous solution with low concentration: Application to broadband dielectric spectroscopy

In this paper we present the investigation results on the dielectric properties of glucose aqueous solutions over a large frequency band spanning from 2 to 18 GHz. The characterization at room temperature (25 °C) of solutions whose concentration varies from 0 to 10 mg/ml is achieved by using an interferometer based near-field microwave microscope (NFMM). The reflection coefficient measured from the evanescent microwave probe (EMP) is mixed with the signal generated from the impedance tuner and therefore recognized to be varied with the glucose concentration. A sensitivity of, at least, 0.15 dB/(mg/ml) and 0.5°/(mg/ml) is demonstrated on the entire frequency range of interest. The best sensitivity being attained for 2 GHz with a maximum value of 0.54 dB/(mg/ml) for the magnitude and 1°/(mg/ml) for the phase shift. We demonstrate that the complex permittivity retrieved from NFMM measured data is in an excellent agreement with the ones estimated by using the Debye model in the investigated frequency range.