Biology Reference
In-Depth Information
11.3 EVLS Increasing the Transducer Potential Range
It has been known that the reduction signals of nucleobases are
overlapped in a wide interval of pH by catalytic hydrogen evolution.
Mixtures of adenine (A) and cytosine (C) have been analyzed at low
concentrations by different methods, for example, by differential
pulse polarography [24] or sinusoidal voltammetry [25]. However,
these methods were not fully successful in resolution of individual
signals. The problem of mixed signals of A and C interfering with
hydrogen evolution has also been evaluated by artificial neural
networks, using linear sweep voltammetry and differential pulse
polarography results [26].
For the resolution of reduction signals of A and C in mixtures,
the EVLS functions eliminating the kinetic current component
and conserving diffusion current component were applied [27].
This approach enables extending a potential range (window) and
monitoring voltammetric signals hidden in the discharge current of
the supporting electrolyte. The essential requirements are fulfilled
by two functions: (i) the EVLS function eliminating the kinetic
current
I
k
and conserving the diffusion current
I
d
(E1) and (ii)
the function eliminating the kinetic and charging currents (
I
k
and
I
d
) simultaneously and conserving the diffusion current
I
d
(E4)
(Table. 11.1). Our results proved that EVLS is an electrochemical
method suitable for the analysis of purine and pyrimidine bases,
providing the reduction signals in the close vicinity of background
electrolyte discharge [27].
11.4 EVLS in Connection with Adsorptive Stripping
Technique
From the definition of AdSV it follows that this method is character-
ized by the nature of the accumulation process, where adsorption
plays an important role [28, 29]. In AdSV, the pre-concentration
step is not controlled by electrolysis, but it is accomplished
by analyte adsorption on the working electrode surface or by
reactions with chemically modified electrodes. From the early
1960s, this technique (in connection with dc polarography and
