Basics of Gas Chromatography

4-2 Baseline Problems

Baseline-related problems can range from column deterioration and contamination to equipment malfunctions. The baseline anomalies were divided into five categories: drift, spikes, noise, instability, and swell. Any problems related to equipment anomalies should be checked in the instruction manual of the equipment.

Drift

Main Causes	Approach
Insufficient column conditioning	Condition the column as described in Handling of Capillary Columns.
Air (water, oxygen) contamination	If excessive drift (baseline rise due to liquid phase stripping) occurs, check the carrier gas.
Degradation of column (liquid phase)	Replace the column.
Insufficient detector equilibration	Wait until the detector stabilizes.
Detector contamination	Clean the detector.

Spikes

Main Causes	Approach
Insufficient column connection (detector side)	This may occur when the column is inserted too far. Check that the column insertion length matches the position specified in the instruction manual of the GC system.
Detector contamination	Clean the detector.
Defective signal cable	Check for contact defects or insulation defects. Replace the cable if necessary.
Faulty electrical cable or power supply	Provide a stable power supply.

Noise

Main Causes	Approach
Detector contamination	Clean the detector.
Contamination of column (liquid phase)	Condition the columns. Cut approximately 50 cm off the inlet side of the column. If there is no improvement, replace the column.
Inlet contamination	This may be caused by liner contamination from inlet septum debris or sample residue. Clean or replace the liner. Replace the inlet septum.
Improper column connection (detector side)	The column might be inserted too far. Adjust the column insertion length to the position specified in the instruction manual of the GC system.
Inadequate carrier gas flow rate	Set the flow rate as specified in the instruction manual of the GC system.
Carrier gas leak (in MS, TCD, ECD)	May be caused by air leakage. Identify and remedy the leakage areas.
Detector failure	Replace or repair any defective filaments, electron multipliers, amplifiers, boards, etc.

Instability and Wander

Main Causes	Approach
Insufficient column conditioning	Condition the column according as described in Handling of Capillary Columns.
Contamination of column (liquid phase)	Condition the columns. Cut approximately 50 cm off the inlet side of the column. If there is no improvement, replace the column.
Inlet contamination	This may be caused by liner contamination from inlet septum debris or sample residue.Clean or replace the liner. Replace the inlet septum.
Detector contamination	Clean the detector.
Detector temperature instability (of TCDs)	Check the temperature stability of the device.
Unstable carrier gas flow rate, insufficient purity	Check the flow rate and gas purity (contamination).
Inappropriate temperature environment around the equipment	Check the ambient temperature.

4-1 Distorted peak shapes

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