I think that what you have is not titanium tetraisopropoxide but titanium oxide resulting from the hydrolysis of the tetraisopropoxide. I suggest using a NaOH hot solution for cleaning.

Thank You for answer! I will try it.

One more question - what concentration of NaOH should it be?

Need to be pretty high, something like 10M.

I started already with 2M. But I will see after weekend, and maybe I will have to enhance it :) Thanks again!

You can use ultrasound batch to improve it. But as you can see it is pretty dificult.

try chromic acid. sonicate after adding chromic acid and leave it undisturbed for a week

I have got some film coating inside a quartz tube due to atomic layer deposition of TiO2 usinf tiitanium isopropoxide and H2O. Which cleaning method is good and what chemical.plsssss help.