ISQ User Guide - Write Frame of Mind

Investigating Baseline Issues
Table 2. Troubleshooting Baseline Issues in Your Data
Behavior Cause Characteristic Remedy
Drifting
Irregular Shape
General
Falling
Rising
Rising baseline when
oven temperature is high
Peak areas are not linear
with concentration
Chromatographic peak is
wrong shape
S-shaped
8 Troubleshooting
Investigating Baseline Issues
Stationary phase has
accumulated in column
Replace the column or cut off the end of the column.
Chromatographic baseline is high Replace the column or cut off the end of the column.
Carrier gas pressure is too low
Carrier gas flow is drifting
Impurities have accumulated in
column
Replace the carrier gas cylinder or increase the
pressure. Make sure the vacuum compensation is on.
Check the carrier gas tank and Digital Carrier
Controller (DCC).
Check impurity levels in your gas. Use the correct gas
purity and filter. Check your septum and replace, if
necessary.
Carrier gas leak in the system
Perform a leak test and tighten the connections to the
carrier gas line.
Column is baking out Wait for the column to stabilize.
Impurities have accumulated in
column
Check impurity levels in the gas source. Use correct
gas purity.
Column is contaminated Recondition or replace the column.
Surface activity or poor sample
preparation
GC column has oxygen or is
damaged, injector port problems
Excessive column bleed at high
oven temperatures
Oxygen contamination is
decomposing the stationary phase
Verify your standards and sample preparation
method.
Trim or change the column.
Change the liner.
Change the column stationary phase.
Reduce the column temperature.
Bake out the column.
Install a high-temperature column.
Install oxygen filters in carrier gas line.
Check pneumatic and inlet systems for leaks.
Use correct gas purity with low oxygen content.
Thermo Scientific ISQ User Guide 91