Starsan and Sour Ferments

[absynthe]

I've started to notice that many of my sour beers will not create a pelicle
until I take my first sample with a sanitized wine thief. I've started to suspect
that the Starsan is introducing O2 to the beer.

Am I wrong? Is there something in Starsan that will cause a pelicle to form?

Is there an alternative sanitizing solution? At lease for sour beers?

Thanks!

 

[Bensiff]

Perhaps it is the opening of the fermenter and the slight draw of air caused by removing some of the liquid volume that is introducing oxygen.