Metrohm 797 VA Computrace - Manual (Page 278)

9 Troubleshooting
797 VA Computrace – Software
266
5. Are organic components present? Carry out a UV digestion or
other suitable sample preparation.
With DME/SMDE:
1.
The concentration of the ion to be determined is too low: use
HMDE (
stripping voltammetry) instead of DME or SMDE.
With HMDE:
1. Has the complexing agent been forgotten? (adsorptive strip-
ping voltammetry).
2. The Deposition time in the inverse voltammetry is too short: in-
crease the time on the Voltammetric tab of the EDIT WORKING
METHOD PARAMETERS window.
3. No Hg drops at the capillary: check MME. Adjust sealing nee-
dle. If necessary, change capillary
and replace sealing needle
(see Hardware Manual).
With RDE/SSE:
1. The background current is too high: try to improve the back-
ground current by electrochemical conditioning. If, necessary,
repolish the electrode. Polishing is only recommended, if elec-
trochemical treatment does not improve the performance of
the electrode
2. The Deposition time in the inverse voltammetry is too short: in-
crease the time on the Voltammetric tab of the EDIT WORKING
METHOD PARAMETERS window.
Peak is in the highest μA range
With all types of electrodes:
1. The concentration of the ion to be determined is too high: re-
duce the sample volume and carry out the analysis again.
With HMDE:
1. The
Deposition time is too long: Reduce the time.
2. If necessary use a SMDE or DME electrode instead of HMDE.
With RDE/SSE:
1. The background current is too high: repolish the electrode.
2. The
Deposition time is too long: reduce the time.
3. Is the Deposition potential correct?
Double peak
With all types of electrodes:
1. Organic components interfere with the analysis: carry out a UV
digestion or other suitable sample preparation.
2. Electrolyte solution too old: make up a new one. Its working
life with organic additives may be as short as 1 day or less.