Use the following API endpoint (at least in v5):
You can query 100 channels at a time, so break your list up accordingly. Remember that it is 2-3 minutes behind when streams actually go live as it is cached data. Do not constantly poll the endpoint though, put a pause between each query.
If wanting to use the New Twitch API:
Again, limited to 100 channels at a time. Rate limits are enforced here so be sure that you are following the rate limit guidelines depending upon the type of authentication you are using.