Measuring delay volume for fraction collector

[john123]

Does anyone have a good way to measure the delay volume for an Agilent fraction collector?

We are interested in determining the volume that gives the highest recovery for closely eluting peaks that are not baseline resolved. We have shortened the tubing as much as possible and can't really optimize the method further.

The internal Agilent methods don't work and we'd sure like to avoid a costly service call.

Thanks in advance for your insights!

[ScottHorn]

For prep scale situations, where the delay volume was around 1-2 ml, I've disconnected the tubing at the outlet of the detector and purged all liquid from it using a luer syringe full of air fitted with the appropriate adapter. I then filled a 1-3 ml luer syringe to a known volume marked on the side of the syringe, connected it to the tubing leading to the fraction collector, and pressed the plunger until I saw the first drop come out of the dispensing head. Subtract the final volume of the syringe to the initial, and Bob's your uncle.
For analytical stuff, I imagine you'd want to rely on the tolerances of the tubing being pretty tight so that you could just calculate it based on the length and diameter of the tubing plus the volume of any flow cells involved in the detection. Then again, if you're doing analytical work you're probably not using a fraction collector. Optimizing dead volume in prep scale stuff is good, but it can only get you so much when the dead volumes are small compared to column volumes. At some point I think you'll want to examine the column itself.