Capillary Columns
Nicholas H. Snow
Department of Chemistry, Seton Hall University, 400 South Orange Avenue, South Orange, NJ
07079
snownich@shu.edu
Capillary/Open Tubular Column
WCOT - Wall Coated Open Tubular
Capillary Column Dimensions
Other Types of Capillary Columns
Tubing Material
• Stainless Steel– reactive
• Glass– can be made inert– difficult to handle
• Fused Silica– flexible– most inert– most popular
Fused Silica Surface
• Contains 0.1% -OH groups
• Very inert• Uniform chemical
surface
Fused Silica
• High tensile strength• Flexible• Sheath of polyimide• Very inert
Capillary vs. Packed
Packed Column - ECD
Capillary Column - ECD
Important Column Parameters
Column Length Recommendations
Stationary Phase Film Thickness
• Starting point: 0.25m• Compromise: resolution and
capacity• Practical operating
temperatures• Speed or resolution
Thick Film Stationary Phase
• Advantages– increased retention for
volatiles
– increased capacity
• Disadvantages– less efficient
– higher temperatures
– higher bleed
Thin Film Stationary Phase
• Advantages– high efficiency
– lower elution temperatures
– fast analysis
• Disadvantages– low capacity
– limited trace analysis
Thin Film SeparationAir Freshener
Stationary Phase Requirements
• Selectivity
• Low Bleed Rate
• Reproducibility
Common Stationary Phasespolysiloxane gum phases
Stationary Phasespolyglycol
Crosslinked Stationary Phases
• More stable• Clean by rinsing• Longer lifetimes
Carrier Gas Flow Rate
Review - Capillary Columns
Review - Capillary Columns