I'm certainly not the most educated person here. Saying as much is either putting words in my mouth, or saying ill-calculated ones from your own.
I am especially not the most informed as it goes to engineering materials or materials science in general. This is a completely different field from my own (organic chemistry).
I am older than your typical grad student and have spent considerably more time in the lab doing research than most--been doing research every semester since undergrad and have been taking school half time/working to pay for it for the last 8 years. So that's 8 years in the lab thus far. I know a good amount about organic chemistry because I have a great mentor--but that doesn't make me believe I've got all the answers.
I've only claimed to have one answer in this thread, and that is the answer to what the word selectivity means. Stumping me about o-rings and what not isn't going to disprove that.
All that said, I'll do some research and see if I can come up with a good answer--because despite your insistence on trying to make me look less intelligent, you've done what I asked at least in part by moving on to a real question about the process moving forward, which is what my interest is in this thread.
As I've said earlier I will only be replying to posts of this nature from here forward.
Have you considered PTFE or HDPE O-rings? I'm not sure about their pressure load capabilities--but I know they are chemical/temp resistent.
Also I've found this:
Here are some details on the material Viton--a fluoroelastomer-- which is used.
VITON® (A) COMPOUNDS
Description: Excellent resistance to petroleum products and solvents. Very good high-temperature performance. Fluorocarbon elastomers make up the most widely
used seals in the semiconductor industry.
Limitations: Avoid polar solvents, amines, anhydrous ammonia, SKYDROL, hydrazine and hot acids.
Chemistry: Copolymer of vinylidene fluoride and hexafluoropropylene, although many more exotic versions exist for improved chemical resistance or low temperature performance.