Not trying to pry anything proprietary from you but have you ever noticed, because you collected the condensed NOx separately, that the distillate contains some gold?
Before I just started to return the condensate to the reactor with gravity, I did a lot of testing using a multi-ratio Corad distilling head. (constant reflux ratio head)
Besides being costly these heads allowed me to take off specific fractions based on the reflux ratio. This is what it looked like.
View attachment 64220
Ironically I learned about this head from Gajda's book on gold refining (quite possibly the worst book ever written on the subject) The image above is from his book.
I did find different reflux fractions did contain different values, but in the long run, I was in the refining business to maximize the returns not to siphon off values. So I just used a straight connection to return all of the condensate to the reaction.
Again, not trying to pry, but I am a nerd and I do notice stuff!