Metrohm 871 Advanced Bioscan - Manual (Page 26)

3 Basic principles
871 Advanced Bioscan / Instructions for Use 8.871.1003
18
3.3.1 Optimization of the PAD parameters
When adapting the method parameters the preset paramete
initially be used. Descriptions of various applications are availa
rs should
ble from
Metrohm AG in the form of Application Works and Application Notes.
These can be obtained from your local Metrohm agency or on the Inter-
etrohm.com net under www.m .
The potential profile shown in Figure 5 must always be matched to the
1, t2 and t3 and the measuring
bas
Measuring int
The measuring pot stigated.
mization then you
reason the 871 Adv
cord the correspon
As each change in
cur at the working
is defined as t1 –
ground current and should therefore be selected so that it is not too
small. In practice a
The measuring inte
The available value
Regeneration interval (E2, E3, t2 and t3)
e required for the regeneration of the
electrode surface are primarily determined by the material of the work-
For example, –800 mV at 0.2 s or –150 mV at 0.4 s can be selected for
Measuring fre
In pulsed amperom
vals (t1 + t2 + t3)
reciprocal of this c
frequency.
analyte under investigation. 7 parameters must be taken into account:
potentials E1, E2 and E3, time intervals t
time ts. Some ic conditions are preset; this makes configuration
easier. These are described below.
erval (E1, t1 and ts)
ential depends on the substance being inve
If no data is available in the literature that can initially be used for opti-
can determine these parameters yourself. For this
anced Bioscan provides the scan mode. How to re-
ding voltammograms is described in Section 3.4.
potential can cause a higher charging current to oc-
electrode, the current measurement itself is only
started when the signal has stabilized itself to a large extent. This time
ts (see Figure 5). It influences the level of the back-
time of 0.1 to 0.4 s is frequently used.
rval ts is selectable with the 871 Advanced Bioscan.
s depend on t1.
The potentials E2 and E3 which ar
ing electrode.
With the gold electrode the oxide layer is formed at E2 > +200 mV
(Ag/AgCl) under alkaline conditions. Higher potentials accelerate oxide
formation, therefore in practice E2 = +750 mV and t2 = 0.2 s are often
selected.
E3 and t3.
quency
etric detection the total of the three individual inter-
represents the duration of one measuring cycle. The
ycle duration (in seconds) gives the possible pulse