Metrohm 797 VA Computrace - Manual (Page 273)

9.5 General rules for VA trace analysis
797 VA Computrace – Software
261
1. DP (Differential Pulse) should always be the first choice. It is
the most universal and frequently used voltammetric determi-
nation method and is equally well suited for reversible and irre-
versible 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 limi-
ted sensitivity (down to 10 -5 mol/L) and a separation ability of
only 1:10. It is mainly used in teaching labs, for the clarification
of reduction/oxidation processes and for stripping voltammetry.
In determination mode DC can only be used with stationary
electrodes (HMDE, RDE).
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, 1st harmonic) is primarily suitable for
determinations based on reversible redox reactions and is virtu-
ally completely insensitive to irreversible reactions.
5. AC2 (Alternating Current, 2 nd harmonic) also primarily suitable
for determinations based on reversible redox reactions. Compa-
red with the AC1 measurements, an increase in sensitivity, re-
solution and separation efficiency is often obtained.
Note: To measure in the AC2 mode, choose AC – Alternating
Current Voltammetry as Mode in the WORKING METHOD SPECI-
FICATION window, click and check the checkbox
2nd harmonic on the Voltammetric tab of the EDIT WORKING
METHOD PARAMETERS window.
6. SqW (Square Wave) is primarily suitable for investigations of
reversible electrode processes and kinetic studies. It is used par-
ticularly for sensitive stripping voltammetric determinations at
the HMDE or RDE.
7. PSA (Potentiometric Stripping Analysis) is mainly used to de-
termine metal traces in aqueous solutions contaminated with
organic matter by means of mercury film electrodes without
prior digestion. Only analytes that form an amalgam can be
analyzed.
8. CCPSA ( Constant Current Potentiometric Stripping Analysis) is
mainly used to determine substances in aqueous solutions con-
taminated with organic matter using mercury film electrodes or
rotating precious metal electrodes without prior digestion.
9. CV (Cyclic Voltammetry) is mainly used to investigate electrode
processes and for kinetic studies.
10. CVS ( Cyclic Voltammetric Stripping) is mainly used for the de-
termination of organic additives in electroplating electrolytes.