Metrohm 757 VA Computrace - Manual (Page 180)

8 Troubleshooting
757 VA Computrace – Software
170
No peak found
With all types of electrodes:
1. The peak is only displaced: adjust the half-wave potential and
recalculate the results.
2. The sample concentration is too low: increase the sample
volume or the amount of sample.
3. Are the Start potential and End potential correct?
4. Electrolyte solution too old: make up a new one. Its working
life with organic additives may be as short as 1 day or less.
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 (inverse voltammetry) instead of DME or SMDE.
With
HMDE:
1. Has the complex former been forgotten? (adsorptive voltam-
metry).
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
needle. If necessary, change capillary or replace sealing nee-
dle (see Hardware Manual).
With
RDE/SSE:
1. The background current is too high: repolish 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.