capillary columns
DESCRIPTION
Capillary Columns. Nicholas H. Snow Department of Chemistry, Seton Hall University, 400 South Orange Avenue, South Orange, NJ 07079 [email protected]. Capillary/Open Tubular Column. WCOT - Wall Coated Open Tubular. Capillary Column Dimensions. Other Types of Capillary Columns. - PowerPoint PPT PresentationTRANSCRIPT
Capillary Columns
Nicholas H. SnowDepartment of Chemistry, Seton Hall University,
400 South Orange Avenue, South Orange, NJ 07079
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: 0.25m• 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
Natural Gas
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
Column Selection