Preparation of stock solutions.


H2O 1ml5ml10ml
  • filter sterilization; or preparation from the sterile water and the sterile powder;
  • store at -20oC in small quantities (about 10 freezing-thawing cycles);
  • instead of H2O it is possible to use 50% glycerol. The advantage - solution is liquid at -20oC.
  • some laboratories use 96% (or 50%) EtOH for ampicillin solubilization. There are two advantages in this method: (i) solution is liquid at -20oC, (ii) the solution is self sterilizing. But the disadvantage it very serious: ethanol is a weak catalyst of b-lactam ring disruption. So, solution is unstable.