Technical barriers to trade, unfortunately even the most robust agreement is never going to completely eliminate these things, because there's no limit to the imagination in terms of being able to create these things. Also, sometimes it becomes the case of who's going to blink first. The degree to which someone will push against the technical barrier is based on the size of the opportunity that's being lost.
Really, in a trade negotiation, you just negotiate as hard as you can. You try to keep as many things on the table as long as you can. You try to find out what you can trade in return for it.
This is going to be tough because it's an emerging economy, but what you can do is you can put provisions into the agreement that any type of barrier that comes to light has to be based on sound science that's recognized by an impartial arbitrator, or panel, or something of that nature. You can actually build this into the dispute resolution mechanism, if you wish.