Chemical identification using an impedance sensor based on dispersive charge transport

Impedance spectroscopy has been used to identify analytes in semiconducting metallophthalocyanine thin films. Above a critical concentration, the magnitudes of the high frequency conductivity changes are invariant with concentration but distinct for different analytes and can be used for analyte identification. The analyte-induced ac conductivity changes above $5kHz$ have been converted to frequency shifts in a circuit resonance and used to differentiate methanol, ethanol, and isopropanol vapors in a nitrogen carrier gas. The analyte-induced changes in the conductivity are consistent with analyte-induced changes in the charge relaxation times.