Looking for suggestions as to the origin of single
broad peak occuring occasionally during analysis of plasma extracts for catechol amines by ECD.
Our system includes a degassor and uses the ESA extraction column, eluant and mobile phase. The eluants are prepared for HPLC by centrifugal filtration.
The interference is not clearly a substance since it usually is not present in a second passage. The deflection in the pattern is broad relative to the catechol peaks and variable in amount of disturbance though less so in time of emergence.

Has someone experience which would point to either the sample handling or injector as a source of this error.

If your chromatographic run is isocratic, the broad peak is a late eluter from a previous injection. Once you see it, try timing your injections to prove the point, then move the injection cycle so it elutes between runs.