If you tell them at the till when you buy it that you are taking it on a second flight the same day, they will put it in a special sealed bag with the receipt in and you will be able to bring it thru security in Dublin.
I bought liquids in a duty free in Norway and brought them thru Heathrow T1 security in the sealed bag and they didn't bat an eyelid, just read the receipt.
Look here under "What about transferring passengers?"
[broken link removed]
I dunno if Fuerteventura is technically in the EU but Norway isn't and they still had the "EU Regulation" bags and there was no problem in Heathrow