Capillary Columns

1
Capillary Columns

• Nicholas H. Snow
• Department of Chemistry, Seton Hall University,
  400 South Orange Avenue, South Orange, NJ 07079
• snownich_at_shu.edu

2
Capillary/Open Tubular Column
3
WCOT - Wall Coated Open Tubular
4
Capillary Column Dimensions
5
Other Types of Capillary Columns
6
Tubing Material

• Stainless Steel
• reactive
• Glass
• can be made inert
• difficult to handle
• Fused Silica
• flexible
• most inert
• most popular

7
Fused Silica Surface

• Contains 0.1 -OH groups
• Very inert
• Uniform chemical surface

8
Fused Silica

• High tensile strength
• Flexible
• Sheath of polyimide
• Very inert

9
Capillary vs. Packed
10
Packed Column - ECD
11
Capillary Column - ECD
12
Important Column Parameters
13
Column Diameter
14
Column Length
15
Column Length Recommendations
16
Stationary Phase Film Thickness

• Starting point 0.25mm
• Compromise resolution and capacity
• Practical operating temperatures
• Speed or resolution

17
Thick Film Stationary Phase

• Advantages
• increased retention for volatiles
• increased capacity
• Disadvantages
• less efficient
• higher temperatures
• higher bleed

18
Natural Gas
19
Thin Film Stationary Phase

• Advantages
• high efficiency
• lower elution temperatures
• fast analysis
• Disadvantages
• low capacity
• limited trace analysis

20
Thin Film SeparationAir Freshener
21
Stationary Phase Requirements

• Selectivity
• Low Bleed Rate
• Reproducibility

22
Common Stationary Phasespolysiloxane gum phases
23
Stationary Phasespolyglycol
24
Crosslinked Stationary Phases

• More stable
• Clean by rinsing
• Longer lifetimes

25
Carrier Gas Flow Rate
26
Review - Capillary Columns
27
Review - Capillary Columns
28
Column Selection