The effects of extra-column volume on 50 and 150 mm columns in 2.1 and 4.6 mm internal diameters were made using a range of capillary tubing volumes installed between the autosampler and column. The results showed that, in using short columns, increases in tubing volume will reduce the column separation efficiency, while increases in tubing volume will have little effect on the separation efficiency of the long column, which is consistent with the results of other scholars.
Agilent Technologies presents a study comparing the effects of extra-column volume on 50 and 150 mm HPLC columns with internal diameters of 2.1 mm and 4.6 mm. The research utilized red (0.12 mm id), green (0.17 mm id), and blue (0.25 mm id) capillary tubing installed between the autosampler and column to measure efficiency changes.
The results indicate that decreases in efficiency range from 1% to 31%, depending on the tubing volume and column dimensions. Larger decreases are observed with 2.1-mm ID columns, whereas 4.6-mm ID columns appear nearly immune to extra-column volume effects. The study concludes that minimizing extra-column volume is essential for achieving best results, particularly when using small-volume columns.
The document recommends using capillary tubing with a 0.12 mm inside diameter.
A detector cell volume of 2 pL or less is recommended.
A significant decrease in efficiency is noted at 7 pL.