Metrohm 746 VA Trace Analyzer - Manual (Page 540)

7.4 Troubleshooting
746 VA Trace Analyzer / 747 VA Stand
7-41
• Enter a new half-wave potential in the instrument and recalculate the results.
• Electrolyte solution too old: make up a new one. Its working life with organic
additives may be as short as 1 day or less.
No peak found
• The peak is only displaced: adjust the half-wave potential and recalculate.
• The background current is too high: repolish the electrode.
• The sample concentration is too low: increase sample volume.
• The deposition time under MEAS in "OP.SEQUENCE" in the inverse voltam-
metry is too short: increase the time.
• Electrolyte solution too old: make up a new one. Its working life with organic
additives may be as short as 1 day or less.
Peak is in the highest µ A range
• The sample volume is too large: reduce the volume. Carry out the analysis
again.
• The background current is too high: repolish the electrode.
• The deposition time is too long: reduce the time.
• Is the deposition potential correct?
Double peak
• Check RDE and polish if necessary (see section 3.5).
• If organic components are present: carry out a UV digestion or other suitable
sample preparation.
• Electrolyte solution too old: make up a new one. Its working life with organic
additives may be as short as 1 day or less.
• Try another measurement mode like AC1. If one substance is reversible and
the second one irreversible, only the reversible substance is detected by
AC1.
Standard addition peaks displaced
• Standard solutions have been made too acidic.
• Buffering capacity of the electrolyte is not sufficient: increase electrolyte vol-
ume.
• Electrode surface overcharged: reduce sample volume.
No addition
• Has the correct standard solution been used or is the concentration of the
solution too low: increase the volume of the standard addition or use a higher
concentration or reduce the sample amount accordingly.
• If organic components are present: carry out a UV digestion or other suitable
sample preparation.
• Concentration of the analyte too high: dilute.
• Electrolyte solution too old: make up a new one. Its working life with organic
additives may be as short as 1 day or less.