Bi-frequency-based microwave liquid sensor for multiple solutes quantification in aqueous solution

This paper presents a technique able to detect and quantify two different solutes in aqueous solution thanks to a single shot microwave measurements of a resonant liquid sensor at two different frequencies. The principle of operation is based on isosbestic characteristics of the sensor relatively to the two considered solutes. The solutes quantification requires a calibration phase. Extracted concentration from measurements leads to root mean square error (RMSE) of only few g/L of solute (3.2 g/L for glucose and 1.7 g/L for sodium chloride). The technique then reveals the potential richness of the spectral signatures from microwave sensor for indentifying and quantifying complex liquids.