What is the most queens that have been on the board in a grandmaster game? There are quite a few grandmaster games with 3 queens or 4 queens, but what is the highest number of queens on the board in a game between two GMs?  

I'd be interested in both the most on the board at the same time and the most total during the game.
This sounds like a job for Tim Krabbé, who presents two games with six queens: Szalanczy - Nguyen, Budapest 2009 and Anton - Franco, XXI Elgoibar Magistral 2011. I don't know how many of the participants were grandmasters.

There are some other games with 5+ queens at Chess Siberia. Of these, Miton - Benjamin, World Open Philadelphia 2005 definitely features two grandmasters.