If the Background Current (BGC) is too high, possible reasons include the following:
If the separation column and/or precolumn are new, please wash the columns with clean analytical mobile phase overnight.
Please check the pH of the mobile phase. Do not dip a pH probe into the bottle. Take some of the mobile phase in a small vial and use the pH probe to check the pH.
A reagent in the mobile phase is not suitable or the ultrapure water has been contaminated. Amuza recommends specific brands for specific reagents, especially for methanol, SDS and SOS as they have been tested in-house. See application manual of your using application for the recommended chemicals.
If methanol is not suitable for ECD, the problem is not significant at the beginning of usage but the BGC gets lower and sensitivity diminishes over time .
If the mobile phase is too old, please replace with fresh mobile phase.
The precolumn/separation column is contaminated. Consider washing the column as outlined in the column manual.
The reference electrode is old. We recommend replacing once a year.
The working electrode is covered by contamination. Try wiping gently with acetone.
If the graphite electrode was applied under a methanol-rich condition, it could be permanently damaged. The graphite electrode can handle a methanol level up to 30% or acetonitrile up to 10% in the mobile phase..
The mobile phase was not shaken well before being set up on the HPLC.
The mobile phase that was used for the previous analysis still remains in the degasser. Use a syringe to aspirate solution from the drain valve of the pump so that the old mobile phase flows out. Disconnect the column and wash the line using clean mobile phase or ultrapure water.
Please double check applied voltage as this can easily be overlooked, especially if there has been any change in application or accidental change to setting.