Microwave dielectrometer application to antibiotic concentration control in water solution

Subject and Purpose. This study focuses on the original waveguide-differential dielectrometer designed for complex permittivity measurements of high-loss liquids in the microwave range towards the determination of pharmaceutical ingredient concentrations in water solutions at room temperature. The suitability of the device and effectiveness of the dielectrometry method are tested on such pharmaceutical ingredients as lincomycin and levofloxacin over a wide range of concentrations. Methods and Methodology. The main idea of the method consists in that the complex propagation coefficients of the HE11 wave are obtained from the amplitude and phase shift differences acquired by the wave after it has passed through the two measuring cells of the waveguide-differential dielectrometer. Results. We have shown that the proposed dielectometry method allows a real-time determination of pharmaceutical ingredient concentrations in water solution by measuring the wave attenuation and phase shift differences. We have found that unless concentrations of pharmaceutical ingredients are low, few free water molecules in water solution are bound to the pharmaceutical ingredients. The number of free water molecules in solution decreases as the concentration of pharmaceutical ingredients rises. Conclusion. The current study confirms that the dielectometry method and the device developed provide effective determination of pharmaceutical ingredient concentrations in water solutions.