Actually, aren't emoticons what you would write with characters, like this: :S
While emojis are a small picture, like 😀
Perhaps you think that because these fancy pictures didn't exist when emoticons were used? :)
Perhaps the API test is checking for Ammonium or Ammonia and Ammonium combined. I don't know what Ammonium you should be looking for-pure NH4+ I would guess, but then again, the Ammonia you added was not 100% NH3, was it?