Metrohm 757 VA Computrace - Manual (Page 176)

8 Troubleshooting
757 VA Computrace – Software
166
Selection of VA Measurement mode
The following points should be considered by selecting the VA
measurement mode:
1.
DP (Differential Pulse) should be always the first choice. It is
the most universal and frequently used voltammetric determi-
nation method and is equally well suited for reversible and ir-
reversible systems. It offers a high sensitivity down to 10
–8
mol/L and a separation ability of 1:50'000.
2. DC (Direct Current) is the classic, simplest VA method with
limited sensitivity (down to 10
–5 mol/L) and a separation ability
of only 1:10. It is mainly used for the investigation of reversible
redox systems.
3. NP (Normal Pulse) is the classic pulse voltammetric VA
method with direct recording of the current. It is equally well
suited for irreversible and reversible systems and offers a
higher sensitivity than the DC voltammetry. The NP mode can
only be used in the exploratory mode.
4. AC1 (Alternating Current, 1 st derivative) is primarily suitable for
determinations based on reversible redox reactions and is vir-
tually completely insensitive to irreversible reactions.
5. AC2 (Alternating Current, 2 nd derivative) is also primarily suit-
able for determinations based on reversible redox reactions.
Compared with the AC1MODE measurements, an increase in
sensitivity, resolution and separation efficiency is often ob-
tained.
6. SqW (Square Wave) is primarily suitable for investigations of
reversible electrode processes and kinetic studies. It is used
particularly for sensitive stripping voltammetric determinations
at the HMDE or RDE.
7. PSA (Potentiometric Stripping Voltammetry) is mainly used to
determine substances in an organic matrix by means of mer-
cury film electrodes without prior digestion and deaeration.
Only analytes which form an amalgam can be analyzed.
8. CV (Cyclic Voltammetry) is mainly used to investigate elec-
trode processes and for kinetic studies.