What is the difference between packed and capillary columns? Or Basic about Gas Chromatography Columns.
There are mainly two type of column used in the Gas Chromatography as a stationary phase:
- Packed Column
- Capillary Column
Basic of this column as described below,
1. Packed column:
- A packed column is one that has a densely packed stationary phase made up of fine particles.
- It’s made of stainless steel or a glass tube with particle packing material within (an adsorbent material, or a support material coated or impregnated with a solid phase).
Material Used in Packed Column: Zeolites
Read: Principle of HPLC (Liquid Chromatography), Calibration of HPLC
2. Capillary column:
- Also known as WCOT (Wall Coated Open Tubular), or PLOT (Porous Layered Open Tubular).
- A capillary column is one that has a stationary phase coated on the inner surface.
- Coateing material includes:
- Methyl silicone
- Phenylmethyl
- Cyanopropyl phenol
- Trifluoropropyl
- Polyethylene glycol Methylpolysiloxane
- Trifuoropropylmethylpolysiloxane
- Bis-cyanopropyl
- Cyanopropylphenylpolysiloxane
Related: Handling of HPLC and GC Columns, Preparation and Standardization of 0.1 N Hydrochloric Acid (0.1 N HCl)
In Gas Chromatography (GC), why are Columns chosen over Packed Columns?
- Gas Chromatography Columns: Packed columns generate broad peaks and capillary columns generate sharp peaks in GC analysis.
- Capillary columns also yield taller peaks, allowing for the detection of lower concentrations (high detection sensitivity). Capillary columns have this advantage. Capillary column produce more theoretical plates (N) than a packed column.
- Capillary column can be used with mass spectrometers because of narrower ID’s.
- New era GC’s designed mostly for use with capillary columns.
- Capillary columns are used in most current methods.
Reference:
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