John, I believe that will be preserved, however did not use liquid nitrogen directly on the sample. I suggest that you put the hemolimph first in -20C freezer, and after 12h / 16h add in the nitrogen tank. I say this because you not have a control of the amount of cells present in hemolimph, and it is the cells that you need to preserve. The cell lysis may cause changes in pH, although I believe that these changes are very discreet.