What do you want?Captain Ivantsov
A short bio, that was being omitted from final version of S.T.A.L.K.E.R.: Shadow of Chernobyl game describes him as follows: 
Shadow of Chernobyl
Captain Ivanstov is stationed at Duty's main base in the Rostok factory area. Ivanstov does not seem to be of any quest-wise significance as he only delivers the quote above when talking to him. Because of this it is most likely that he is only in the base as a guard.
Behind the scenes
- In Shadow of Chernobyl's unused scripts, Ivanstov was originally supposed to be the one to induct the player into Duty if one chooses to join them, as mentioned in his dialogue.