GC
GC Column Selection Guide for Routine Analysis — Analytical Instrument Guide
How stationary phase, film thickness and column dimensions affect separation - and how to pick a sensible starting point.
Choosing a GC column is a trade-off between resolution, analysis time and column lifetime. Here's a practical starting point for routine methods.
Stationary phase
- Non-polar (100% dimethylpolysiloxane): general-purpose, good for hydrocarbons and non-polar compounds.
- Slightly polar (5% phenyl): the most common general-purpose phase, works well for a wide range of routine methods.
- Polar (polyethylene glycol / wax): better for alcohols, free fatty acids and other polar analytes.
If you're developing a new method and unsure, a 5%-phenyl column is a reasonable default starting point.
Column dimensions
- Length: longer columns (30m+) give better resolution but longer run times. 30m is a common default for routine work; 15m columns suit fast screening methods.
- Internal diameter: narrower bore (0.25mm) gives better resolution and efficiency; wider bore (0.32mm) tolerates more sample and is more forgiving for routine, high-throughput labs.
- Film thickness: thicker films (1-5μm) suit volatile analytes and give more capacity; thinner films (0.1-0.25μm) suit less volatile, higher-boiling compounds and give sharper peaks.
Practical tips
1. Match the column to the method reference where one exists (pharmacopeial and regulatory methods usually specify phase and dimensions). 2. Keep a spare, pre-conditioned column of your primary method's type on hand - column failure mid-batch is one of the most common causes of unplanned downtime. 3. Track injections against the column's rated lifetime, especially for dirty matrices - proactive replacement is cheaper than a failed batch.
Need a column for a specific method? Send us the method reference or your current column part number and we'll match a compatible replacement.