I want to separate plasma from mice blood and store plasma sample for long time. In which process the viability/validity of my sample will be same as fresh sample?
An anticoagulated blood separated by centrifugation and careful removal of the plasma could be stored in aliquots at -30°C or lower, with the composition of the plasma not significantly not affected by storage for a long time. This is what I know of human plasma, which I think may work for mice plasma as well.
Serum also can be used. Let blood coagulate the clot retraction increase the yield of remain serum between cells, Centrifuge and store at -20 to -30 ºC.