HP 5890 Series II Plus Reference Manual page 212

Chromatographic Troubleshooting
Peak symptoms
3. Top (apex) of the peak is deformed:
Figure 9-3.
Detector Overload
212
Interaction with column material is a frequent cause. Silanized
support may help. An all•glasssystem may be required if metal
column tubing is the source.
Column overload with a gas sample often shows this effect; try
injecting less.
This may be a merged peak situation: Running at lower (30 C)
oven temperature will increase resolution, perhaps enough to
reveal merged peaks.
Low inlet temperature may cause this, as can poor injection
technique.
Detector overload is the probable cause: The distortion is not
easily seen on the chart but reveals itself in an integrator report.
In extreme cases, doubling amount injected causes little or no
increase in peak size.
Inject less sample, or dilute it, whichever is more convenient
(dilution is usually the best approach). Since the detector is at the
upper limit of its response, substantial dilution (100 times or
more) is needed to be well within normal operating range of the
detector.