Ants in the kitchen are a colony problem, not an individual ant problem. Killing the ants you see does nothing. You have to eliminate the colony.
Clean every counter and put all food in sealed containers. Place Terro bait stations directly on the ant trails — along baseboards, near the sink, wherever ants are congregating.
Leave the ants alone when they're feeding on the bait. They need to carry the liquid back to the colony. Killing them at the bait station defeats the entire purpose.
Spray all countertops with vinegar and wipe clean. Once the infestation is gone, seal cracks and gaps where ants were entering with caulk.
Terro bait typically eliminates a colony within 24-72 hours. More ants initially means it's working.