I had some ants in both my home and shop. I made my own insecticide from Boric Acid, Sugar and Water. I soaked it up in cotton balls and stuck the balls in bottle caps and set them in the infested areas. It took a few days but that was almost a year ago and they never returned. You want to make it weak enough so that they live to take it back to the queen. I'm not sure whose recipe I followed but there are many on google. Here's one of them:
Boric acid powder mixed with sugar will help eliminate ant problems. Make the insecticide bait by mixing 1 part of boric acid with 9 parts of sugar. Stir the mixture into a small bowl of water until the powder is dissolved. Soak cotton balls in the liquid. Purchase small, plastic, disposal food containers to hold the bait. Punch holes in the container to allow the ants access. Place the soaked cotton balls on the inside and seal with the lid. Place the containers anywhere you suspect ant activity. The worker ants will carry the boric acid back to the queen and the entire colony will be eliminated. An article by Howard Garrett in "The Dallas Morning News" advises against using too much boric acid in the baits. Baits with more than 10 percent boric acid will make the mixture distasteful, thereby defeating its insecticide purpose.
It really worked and lasted for me.