Nasal spray with midazolam, due to limited availability of preservatives, can I use cnk 1756238 (phosphate buffer for Xylometazoline)?

For a child I have to make a nasal spray with midazolam, I found in the question box a prestsel, but Nipagine is no longer in trade, like a proposal for a preservative in trade. Or should I possibly use phosphate buffer for xylometazoline?