Two HILIC questions

[meow]

1) If I run 90 or 95% AcN over a HILIC column, and then inject a short plug of pure AcN without water / buffer, will this short plug destroy the HILIC hydration layer? Say I run at 200 uL/min at 90% AcN and I inject 20uL pure AcN.

2) Similarly, if I inject pure 0.1% formic acid in water (with the goal of eluting everything. Don't ask why, I have my reasons) will this 1) permanently impact the HILIC phase, and 2) how long will I have to run 90% AcN to restore HILIC behaviour?

Thanks
-meow

[Andy Alpert]

1) It won't destroy (= strip away) the hydration layer. That layer is tenaciously held; you'd have to run in 100% ACN for some time to leach it all away. That said, you might perturb it enough to affect the reproducibility of retention times for several minutes.

2) 1) No (but please state which HILIC column you're using); 2) Between 35 and 50 minutes if you want to reestablish the reproducibility of retention times of early-eluting solutes.