GC Columns

 GC Columns

Capillary columns were first used and patented by Golay in 1958/9, but were not widely used until the late 1970's, after which they have steadily grown in popularity. Today the vast majority of GC applications are developed or run using capillary columns. The selection of the correct stationary phase is one of the most critical parameters in the success of any GC method. The aims of this module include the comparison and contrast of packed and capillary columns. A revision session of of fundamental intermolecular interactions is included in order to relate the various types of interaction to retention in GC. We will explore various stationary phase types and explain the critical factors in choosing a phase. The important physical parameters of capillary GC columns and their relationship with retention, resolution and efficiency in GC separations is investigated. Column bleed and how to minimize it is introduced, and good practice for column installation and conditioning highlighted. 

At the end of this unit you will be able to recognize and explain the various interactions that occur between analytes and stationary phases in GC, select an appropriate stationary phase for various analyte and application types, select appropriate column dimensions for various application types, demonstrate a good understanding of how to manipulate column physical parameters in order to obtain good quality separations in a reasonable time frame, and explain the principles of good column handling, installation, and conditioning in a practical context.

Topics include:

Open tubular capillary columns

Comparison of packed and capillary columns

Chemistry review - analyte and stationary phase polarity

Electronegativity

Dispersive interactions

Dipole interactions

Hydrogen bonding

Stationary phases - polysiloxanes

Polysiloxane classifications

Stationary phases - polyethylene glycols

Stationary phase selection

Phase selection - dispersive phases

Phase selection - dispersive interactions and polarity

Phase selection - diople interactions and hydrogen bonding

Stationary phase selection - PLOT columns

Stationary phase selection summary

Stationary phases for packed column GC

Column dimensions- length

Column dimensions - internal diameter

Column dimensions - film thickness

Column dimensions - phase ratio

Carrier gas flow rate

Column bleed

Column installation and conditioning

Exercises in column selection