THE INFLUENCE OF ELECTRODE POLARIZATION ON DIELECTRIC SPECTRA, WITH SPECIAL REFERENCE TO CAPACITIVE BIOMASS MEASUREMENTS - (II) REDUCTION IN THE CONTRIBUTION OF ELECTRODE POLARIZATION TO DIELECTRIC SPECTRA USING A 2-FREQUENCY METHOD

Electrode polarisation can interfere significantly with the measuremen t of the dielectric properties of biological systems, and in particula r with the dielectric estimation of microbial biomass. We showed in th e previous paper of this pair [C.L. Davey, D.B. Kell, The influence of electrode polarisation on dielectric spectra, with special reference to capacitive biomass measurements: I. Quantifying the effects on elec trode polarisation of factors likely to occur during fermentations, Bi oelectrochem. Bioenerg., 1998] that electrode polarisation can be mode lled by a power law and that the parameters of this model can be simpl y modified to give reliable and intuitive measures of the magnitude (C -L(P)) and rate of fall of polarisation with increasing frequency ((h) f). Importantly and surprisingly, although the (h)f value remained con stant. A highly useful consequence of this magnitude of electrode pola risation can change it was found that the constancy of (h)f for a give n instrument is that one can exploit it directly to eliminate electrod e polarisation from biological capacitance (or permittivity) spectra u sing the simple two-frequency method developed in this paper. (C) 1998 Elsevier Science S.A. All rights reserved.