# Extra Column Dispersion - GC Capillary Columns > Page 10

# GC Capillary Columns

The maximum permissible extra column dispersion for a GC capillary column must be corrected for the compressibility of the mobile phase and the alternative geometry of the tube,

Thus, for a GC capillary tube, equation (3) becomes

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and equation (4) becomes

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In a similar manner, the maximum sample volume that can be placed on a GC capillary column, assuming half the permissible extra column dispersion is allotted to sample volume, follows directly from equation (6) which becomes