elementist bosses

where is the best element bos to use sig of capture on im a lvl 16 ele/monk i just got to i just finished villany quest so whatever the closest city to there is thats where i am

Each boss uses a different spell, so asking which is the best to use your Cap. Sig. on isn't a very good question at all. Which spells are the best is a highly subjective matter. You're better off checking out which elite you want and going after the boss that has it.

http://www.xennon.co.uk/eliteskills/

If you are still in Kryta or Maguuma you might want to wait until the desert missions. I believe that is the first place you can cap an elite. If you are doing the cap quest it's really worth it to wait for the elite cap. I believe all 3 desert missions give you the same elite so it won't really matter which one you cap in. Just be sure to finish the mission first and go in again and cap after you've finished it.