Fractional frequency domain identification of NaCl–glucose solutions at physiological levels

• A general methodology to develop impedance measurements in presence of non-linear distortions is employed.
• Glucose at physiological concentrations affects the impedance significantly regarding the noise level of the measurements.
• We develop integer and fractional parametric models in the frequency domain for impedance measurements.
• We show that the fractional model allows a better mapping the glucose changes.

Electrical impedance spectroscopy (EIS) has been used to characterize different biological materials. This article exposes a methodology oriented to estimate glucose levels of a solution based on a rational fractional parametric model of the impedance data. The methodology is applied over saline–glucose solutions at five physiological glucose levels, using three sensors and five repetitions for each glucose concentration and employed sensor. The results suggest that changes in the glucose concentration produce significant changes in the impedance that should be reflected in the parametric model. The modeling procedure shows that the poles and zeros of an integer model presents a degree of correlation. However, the correlation is clearly explicit employing fractional models where the mean location of the complex zeros is highly related to the glucose content in the sample.