Metrohm 871 Advanced Bioscan - Manual (Page 24)

3 Basic principles
871 Advanced Bioscan / Instructions for Use 8.871.1003
16
3 Basic principles
3.1 Introduction
can be operated as an amperometric de-
s are oxidized or re-
.
easured.
Scan mode Current-potential curves are recorded in order to de-
termine the optimum parameters for amperometric
e.
• nt potentials are applied cyclically to
the electrode sur-
face from any adhering reaction products and reac-
this is the
used with the 871
is
described in detail in Section 3.2.
3.2 Measuring
Amperometric detection takes place with a flowing current and there-
ion of the analyte. The course of a chemi-
er to obtain optimum measuring conditions (e.g.
stable baseline or reproducible signals) it is necessary to take the fol-
l
working electrode
(oxidation and reduction) are influenced by the tem-
nt temperature is a neces-
sary precondition for obtaining a stable baseline
cible signals. For the determination of
s (30 °C – 35 °C)
w cell should not
r time period.
• pH so
has a direct influence on the electrochemical reac-
tions at the working electrode. pH alterations cause
The 871 Advanced Bioscan
tector in three different working modes:
• DC mode A constant potential is applied to the working elec-
trode. The analyte substance
duced according to their electrochemical properties
The current that is produced is m
•
detection (DC and Pulse). This is done by passing a
solution that contains only the substance of interest
through the measuring cell and recording a current-
potential curv
Pulse mode Three differe
the working electrode. This frees
tivates it for the next measurement. As
operating mode that is primarily
Advanced Bioscan for carbohydrate analysis it
conditions
fore with a chemical convers
cal reaction depends directly on various physical parameters, among
other things. In ord
owing points into consideration:
• Temperature The reactions occurring at the
perature. However, this applies not only to the con-
version of the analyte, but also for interfering reac-
tions that produce the background current. This is
the reason why a consta
and reprodu
carbohydrates, lower temperature
are suitable. Furthermore, the flo
be operated above 45 °C over a longe
Just like the temperature, the pH of the eluent al