Effect of heat exchange capillary length on retention time

[SamNas]

What is the effect of length of heat exchange capillary on retention time

[bunnahabhain]

Depends a lot on column dimensions and flow rate.
If you go from 3 uL to 12 uL you will have little to no effect on a 250x4.6 mm column with flow rate 2 mL/min but noticeable effect on a 50x2 mm column with 0.2 mL/min.

[SamNas]

Will RT increase or decrease if length of heat exchange capillary is increased?

[bunnahabhain]

Increased lenght means increased extra column volume, therefore it will also increase the RT.

[lmh]

I suppose what SamNas might also be hinting at is whether the actual temperature-pre-equilibration will be affected by the length of the heat-exchange capillary, and what that will do to retention times.

I have no idea, but at 2mL/min the time spent by solvent in a 3uL capillary is less than a tenth of a second, so I suppose it's possible the solvent isn't going to be fully equilibrated?