You should be able to tell if there's a nest in one or more of the pots - when there is, there's always black flecks of soil around the base of the pot. But if your plants otherwise look healthy,it seems unlikely there's a large ants' nest in any of them. You can check by raising the pots off the ground slightly, on pot feet or anything you've got that will achieve half an inch clearance beneath - you'll see ants coming and going under there if they are in the pots. Dusting with ant powder beneath helps to deter ants under pots. Otherwise, they'd be climbing up the sides of the pot to get back to the nest.
The point is, though, ants in themselves are not a problem. If they're on your plants, its because there's something there they like, like aphids or scale insect, and they want to harvest the honeydew. Killing all ants just in case, at a later date when the insects infest the plants, they want to harvest the honeydew is next to impossible, frankly. And you'd still have an aphid or scale problem ...And whilst ants might occasionally move an aphid or two from one branch to another on a plant, they don't march along in rows carrying aphids to infest your plants - the aphids fly in by themselves.
If you want to try, about the only thing that might make a small difference is using Nippon, from a tube - you drop some of it onto a coin or something and leave it where you know they travel. They eat the Nippon and take it back to the nest, which, in theory, kills the nest. In reality, it's unlikely to kill everything in the nest. Given you're not applying the Nippon to your plants, it doesn't matter that it contains insecticide, if you really fancy attempting mass murder! You can buy Nippon tubes on their own, or use a fancy trap with it https://www.amazon.co.uk/Nippon-Control-System-Killer-Liquid/dp/B000TAW31A, though these are really intended for indoor use.
Ants like sweet things, like honey or jam; you could try putting some in dishes that they can't climb out of afterwards, or mix the jam/honey with water in a jar and hope they find it. I've never found that particularly successful, you just get a small number of ants floating around in the water, usually along with the odd bee or three. And I suspect floating around in sugary water is no more pleasant for the ants than snacking on Nippon...