Compensating for Electrode Polarization in Dielectric Spectroscopy Studies of Colloidal Suspensions: Theoretical Assessment of Existing Methods

Abstract

Dielectric spectroscopy can be used to determine the dipole moment of colloidal particles from which important interfacial electrokinetic properties, for instance their zeta potential, can be deduced. Unfortunately, dielectric spectroscopy measurements are hampered by electrode polarization (EP). In this article, we review several procedures to compensate for this effect. First EP in electrolyte solutions is described: the complex conductivity is derived as function of frequency, for two cell geometries (planar and cylindrical) with blocking electrodes. The corresponding equivalent circuit for the electrolyte solution is given for each geometry. This equivalent circuit model is extended to suspensions. The complex conductivity of a suspension, in the presence of EP, is then calculated from the impedance. Different methods for compensating for EP are critically assessed, with the help of the theoretical findings. Their limit of validity is given in terms of characteristic frequencies. We can identify with one of these frequencies the frequency range within which data uncorrected for EP may be used to assess the dipole moment of colloidal particles. In order to extract this dipole moment from the measured data, two methods are reviewed: one is based on the use of existing models for the complex conductivity of suspensions, the other is the logarithmic derivative method. An extension to multiple relaxations of the logarithmic derivative method is proposed.

Predicting the Dielectric Response of Saturated Sandstones Using a 2-electrode Measuring System

“…Electrode polarization (EP) is observed at low frequencies in a 2-electrode measurement system and arises due to ion buildup close to the surface of the electrodes, as both electrodes are considered to be blocking. This effect is associated with a characteristic frequency ω ep , which is defined as [11,14]…”

“…In this article, C s is in the range 5-540 mM, and two electrodes separations are used: d = 0.03 m and d = 0.074 m. The characteristic frequency for the EP effect is, thus, in the frequency range below 1 kHz (from Equation 8). EP complex conductivity can also be derived from the set of electrokinetic equations presented in Buck [11] and Chassagne et al [14]. The expression for EP reads…”

“…For electrolyte solutions (no porous media), ε ep = ε e . In the case of two-phase systems, such as suspensions or porous media made of electrolyte and grains, it remains to be investigated if [14], where ε b (ω) is the dielectric permittivity of the two-phase system that is connected to the bulk conductivity (Equation 1).…”

“…Electrode polarization (EP) is the most common electrode/bulk effect reported in the literature for dielectric spectroscopy measurements, which are conducted with 2electrode systems [11][12][13][14]. This phenomenon occurs due to the build-up of ions close to the surface of the electrodes (which are assumed to be perfectly blocking) at low frequencies.…”

Changes in biosynthesis of exopolysaccharide in Lactococcus lactis subspecies cremoris treated by moderate pulsed electric field treatment

“…2(A), while the pulse voltage was controlled at 8 kV/cm for 1 μs, the pulse current reached to 9.7 A, which decayed after 4 μs. In order to analyze the dielectric relaxation during the PEF treatment, 24,25) the impedance spectra for relative permittivity (ε′) and dielectric loss (ε′′) of the ferment were shown in the Fig. 2(B).…”