Electrical Impedance Spectroscopy (EIS) characterization of saline solutions with a low-cost portable measurement system

Electrical Impedance Spectroscopy (EIS), a powerful technique used for wide range of applications, is usually carried out by means of benchtop instrumentation (LCR meters and ìmpedance analyzers), not suited for in-the-field measurements performed outside a laboratory. In this paper a new portable electronic system for EIS on liquid and semi-liquid media is presented that is capable to produce an electrical fingerprint of the sample under investigation. The proposed system was used for the characterization of four different saline solutions (NaCl, Na2CO3, K2HPO4and CuSO4). A multi-frequency approach, based on the measurement of maximum value of the impedance imaginary component and its corresponding frequency, was tested for the first time to discriminate different saline solutions. The results show that the proposed method is capable to discriminate the different solutions and to measure the concentration (R2= 0.9965) independently of the type of saline solution.