Whats the premium butane on the market in 2016?

I have a friend who does very low quantity, but high quality extraction in a fairly remote area where it's hard for him to get ahold of concentrate. Combusting flowers gives him all kinds of mucus but he has had very good results using BHO for his medicinal purposes. He was using puretane from a local smokeshop and he was having pretty good results, however his local shop no longer carries the brand and has converted to something called StOK. He tried a couple experiments with this new butane but has not been satisfied with the flavor or the purging time. I know there are purity reports out there for various brands of butane, but they seem to be fairly outdated, and not so professional or scientifc. What do you guys recommend for maximum terp containment and minimal purge time in 2016?

all precautions are being taken when performing this experiment. No open flames, clean glassware, outdoor extraction, and purged in a well-ventilated area for an extended period of time.

We re-distill and filter 99.5% Praxaire Instrument grade, to produce 99.995% purity. We get our Praxaire from Apis Labs in Eugene, OR; [email protected].