Introduction to the Agilent 7100 Capillary Electrophoresis System

Troubleshooting and Diagnostics 6
CE Problem Solving
Blocked Replenishment Needle
If you are using the replenishment function of the Agilent CE instrument,
buffer may precipitate inside the replenishment needle. To avoid this, put a
vial filled with water or buffer (to a height of 1.8 cm) in vial position 49. Vial
position 49 is the home position of the replenishment lift. The vial will be
picked up by the lift and brought to the replenishment needle. The needle will
dip into the water, thus preventing the buffer from precipitating. (see
“Preparing Vials for Buffer and Sample” on page 115, Vial position 49)
Leakage Current
Leakage current is indicated by a yellow bar in the current part of the energy
status display in the CE diagram. Only high leakage current will lead to this.
An instrument curve allows you to monitor current leakage even at low values
from the ChemStation.
Leakage current means that the current at the inlet electrode is different from
the one at the outlet electrode and thus a current flows outside the capillary.
A certain leakage current must be regarded as acceptable, since it is not
avoidable due to technical reasons.
It can be caused by:
• A broken capillary
• An empty inject vial
• An air bubble in injection vial/or run buffer vials
• An air bubble in capillary
• A contaminated insulation plate
• A high humidity level
• A conductive capillary surface
If you find a broken capillary in the alignment interface, use an ultrasonic
bath to clean the interface and remove quartz residues.
Agilent 7100 Capillary Electrophoresis System User Manual 165