We are analyzing CO2 after reacting carbonates with 105% phosphoric acid
at 75 degrees for 15 minutes.

Would like some advice with the following basic issues:

1. We currently use boro-silicate rxn tubes, with screw piston type top
and Apiezon grease in between.  I recently replaced the o-rings on the
pistons with nitrile o-rings, but am having problems keeping atm from
slowly leaking in at times; any suggestions on optimal o-ring material?

2. To isolate sample from acid during evacuation, we place our samples in
a small plastic cap made of polypropelene; is there a more appropriate
choice than polypropelene?

Thank you for any suggestions.