There was another question few days ago on the same issue. You may wish to have a look at that. It is on the next page. But this is what I suggested there, have a go and it would work.
Try this and you would never have problem with ants. Depending upon where you live if you can get a hold of ground turmeric (Called Haldi on Indian or Pakistani shops). It is yellow color powder which is used almost in all Asian dishes. Just sprinkle a little bit where you see ants. They will never come back there again.
http://en.wikipedia.org/wiki/Turmeric