Detection of an emerging contaminant in water by dielectric properties in microwave range

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The complex relative permittivity study of samples of liberdux® syrup dissolved in distilled–deionized water is presented. It should be mentioned that excess of this syrup as pharmaceutical residual in water is considered an emerging contaminant. The study covers liberdux® concentrations from 0% v/v to 100% v/v, which were measured from 500 MHz to 20 GHz. For each sample, the parameters of the Havriliak–Negami model are presented in the range of measurement. Also, the uncertainty study was carried out to determine the sensitivity of the open coaxial probe and it was established that, for concentrations between 8% v/v and 100% v/v, it is possible to determine the concentration of liberdux® in water by the dielectric constant and the loss factor. In addition, a linear relationship was found between the concentration of liberdux® and the α parameter of the Havriliak–Negami model. The study of liberdux® concentrations was also performed with a spectrophotometer and the Beer–Lambert equation. It was established that the spectrophotometer and the open coaxial probe can be used as complements to measure concentrations, the spectrophotometer being the instrument for measuring low concentrations by absorbance, and the open coaxial probe for high concentrations by microwave permittivity.