Capillary Columns Nicholas H. Snow Department of Chemistry, Seton Hall University, 400 South Orange Avenue, South Orange, NJ

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 Diameter

Column Length

Column Length Recommendations

Stationary Phase Film Thickness Starting point: 0.25  m 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

Natural Gas

Thin Film Stationary Phase Advantages –high efficiency –lower elution temperatures –fast analysis Disadvantages –low capacity –limited trace analysis

Thin Film Separation Air Freshener

Stationary Phase Requirements Selectivity Low Bleed Rate Reproducibility

Common Stationary Phases polysiloxane gum phases

Stationary Phases polyglycol

Crosslinked Stationary Phases More stable Clean by rinsing Longer lifetimes

Carrier Gas Flow Rate

Review - Capillary Columns

Column Selection