Retention Gaps
Key features
The retention gap technique in combination with on-column injection allows to concentrate a large sample volume in the capillary column.
Choice of the retention gap depends on the solvent used: the looded zone after injection should be between 20-30 cm/μL
Me-Sil retention gap: only for use with n-hexane and diethyl ether
Phe-Sil retention gap: for all solvents except methanol and water
CW retention gap: for all solvents and especially for methanol and water
Temperature
Max. Temp. 250 °C (CW retention gaps).
Max. Temp. 320 °C (Me-Sil and Phe-Sil retention gaps)
Note:
Calculation example: length of flooded zone ~ 20-30 cm/μL, retention gap 10 m x 0.32 mm ID, capillary column: 25 m x 0.32 mm ID, max. injection volume ~ 30-50 μL
A retention gap must be inert without any noticeable retention: Me-Sil retention gaps are more inert than Phe-Sil, while Phe-Sil is less susceptible to contamination
Retention gaps can also be used as transfer lines or pre-columns (contamination capacity about 5-10 μg).