How to determine antimiony in TiO2

Can anyone tell me a method for antimony determination in titanium dioxide (by ICP-AES or AAS)?
I follwed the method dicribed in TiO2 Monograph USP, but I could not detect Antimony in TiO2.

USP TiO2 Monograph
Specification limit: < 2ppm

Please tell me good tip for the method.