Even if it were possible to obtain pure goldenseal root, it is not something
I'd want to put into the far reaches of my sinuses.

I used this method for a kitten that had a sinus infection and it
helped a lot.  I have
used the liguid herb on myself in a saline but it didn't help much.

I used to sometimes orally take a tincture of Goldenseal for sinus
problems, and it generally always helped.  I stopped, however, when I
read that people with pollen allergies should not use Goldenseal.  Even
though I hadn't had problems with it, I didn't want to take that risk.
I would think that irrigating with it would be even riskier for those
with pollen allergies, so I'd stay away from it if you think you have
such allergies.

It still doesn't seem like something to put up your nose, but you might
want to try using it in tincture form.