Question

How does the column diameter and film thickness affect the capacity of a GC column. List a circumstance where you would want a thick film and another where you would want a thin film.

Answer 1

Increased diameter means more stationary phase, even with the same thickness, for greater sample capacity. It also means reduced resolving power and greater bleed.

Stationary phase thickness (μm) directly affects retention, resolution, and elution temperature for each sample component. Thickness will primarily affect the retentive character and capacity of a column. Increasing film thickness will cause a substantial increase in the retention of a solute.

Use thin film columns for high boiling solutes such as petroleum waxes, triglycerides, steroids, etc.

Use thick film columns for very volatile solutes such as gases, low boiling solvents and purgeables.