Impedance spectroscopy of solutions at physiological glucose concentrations.

Impedance spectroscopy has been proposed as possible approach for non-invasive glycaemia monitoring. However, few quantitative data are reported about impedance variations related to glucose concentration variations, especially below the MHz band. Furthermore, it is not clear whether glucose directly affects the impedance parameters or only indirectly by inducing biochemical phenomena. We investigated the impedance variations in glucose-water, glucose-sodium chloride, and glucose-blood samples, for increasing glucose values (up to 300 mg/dl). In all the frequency range (0.1-10(7) Hz) glucose-water samples showed impedance modulus increases for increasing glucose values (up to 135%). In blood and sodium chloride samples the impedance modulus showed only slight variations (2% and 1.4%), but again in wide frequency ranges. Therefore: i) glucose directly affects the impedance parameters of solutions; ii) effects are more relevant at frequencies below the MHz band; iii) the influence on the impedance is decreased in high conductivity solutions, but still clearly present.