You have not stated how you made the butylbromide. I take it the product is in a solvent?
If you made the product using a PBr3 bromination of butyl alcohol then a small scale work up is to pour the mixture onto iced water and extract with a solvent. The aqueuos phase will become very acidic (phosphoric acid and HBr) and some of this acidity transfers to the aqueous phase. The washing with bicarbonate will then remove the acid from the aqueous phase. It will also remove traces of bromine (slight yellow colour) in the product as well. Bromine can be a by-product of the reaction.
If you use NaOH some of the butyl bromide will be converted to butyl alcohol.