Electrochemical Detection - Waterborne Pathogens: Detection Methods and Applications - page 139

function of the applied solicitation giving access to the electrochemical
impedance of the system. In such conditions, any type of perturbing signal
(i.e. sine wave, step, etc. …) gives the same information. The advantage of
nonsteady-state conditions (i.e. variation of the amplitude or frequency of
the solicitation) is their capability to separate the contributions of the vari-
ous phenomena in the overall response of the system. Finally, distinction
can be made between static (i.e. no charge flow) and dynamic (i.e. charge
flow) conditions.
Historically, many electroanalytical techniques have been developed,
and it may be difficult to understand their specificity for the newcomer in
this field. However, they can be classified in four main categories: potenti-
ometry, voltammetry, coulometry and impedancemetry. 7 These techniques
use two, three, or four electrodes depending on the specific measure-
ment conditions. The material of the electrode has to be chosen carefully
because it has a direct effect on the electrochemical reactions at the inter-
face. Potentiometric measurement is a static technique and is discussed in
Section 6.2 . The three other techniques are dynamic and can be carried out
either in steady or nonsteady-state conditions. In voltammetry (see Section
6.3 ), the current is measured as a function of a fixed or variable potential.
In coulometry (see Section 6.4 ), the current is measured as a function of
time. In impedancemetry (see Section 6.5 ), the current is measured as a
function of voltage frequency. In parallel to these four main electrochemi-
cal techniques, the biosensing community is showing a growing interest
toward dielectrophoresis (see Section 6.6 ). This technique uses two, four,
or eight electrodes to build a 3D, static or dynamic, and nonuniform map
of the electric field within the sample. The interaction of the electric field
with the particle dipole induces a linear or rotational displacement that
can be used to characterize the particle. Scaling down of the electrodes is
a very active research field driven by the recent progress of miniaturiza-
tion technologies. However, the isomorphic reduction of the dimension of
the electrode has a direct effect on the relative importance of the various
physical phenomena that can be electrochemically monitored as discussed
in Section 6.7 . Section 6.8 gives a review of the literature of how the
above techniques have been applied to pathogen detection, in particular
waterborne pathogens, and what are the current developments that would
definitely impact electrochemical techniques in the near future. The chap-
ter is briefly summarized in Section 6.9 and is concluded with perspectives
on the potential use of these electrochemical technologies in waterborne
pathogen detection.