Xylometazoline Nasal drip without preservatives

As a result of the lack of is droplets for baby without preservative I would like to make these myself. Can I simply omit from the TMF formula Xylometazoline 0.025% The Benzalkonium but that the Isotonia remains within the right limits? I do not have a table with E-values so it cannot calculate itself. If you have such a list, you can always deliver it to me. Secondly, how long would such a solution remain good? With freshly boiled water, 1 month? Thank you very much for your reply.