We are storing plasma samples (after separatoin from whole blood) in classical 15  ml polypropylene tubes at -80 for years or 1.5 ml eppendorf tubes or as well in cryovials. With regards to the serum antibodies we haven't observed any negative effects from prolonged incubation at very low temperatures or at 4C in these tubes. For many applications you may want to make sure you use serum (defibrinated the plasma) as otherwise the undiluted plasma will tend to solidify in contact with certains plastic types. 

We keep serum in 1.5 or 2 ml eppendorf tubes at -80 degree C for cytokine analysis and at -20 degree C for immunoglobulin analysis.

I would seal them in ampules and flame the tops closed. 

Thank you all for your helpful response

Respected Debaki Ranjan Howlader , can you plz provide the reference for the same. thankyou