Boston University 2006:making antibiotic stocks


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Use the following protocol to produce 5 1mL aliquots of stock solution of your desired antibiotic. Use a 1:1000 dilution to reach a working concentration from the stock (i.e. take 5uL from the Amp stock and add to 5mL of LB broth to produce 100ug/mL Amp + LB broth).


  • Powder of given antibiotic
  • dH20 and/or 100% ethanol
  • 5mL Falcon tube(s)
  • 5 1.5mL microcentrifuge tubes (per 5mL falcon tube)


Common antibiotic stock & working concentrations
Antibiotic Abrv. Working Stock Notes Color Code
Ampicillin Amp 100 ug/mL 100 mg/mL orange
Chloramphenicol Chm 30 ug/mL 30 mg/mL in 100% ethanol green
Kanamycin Kan 50 ug/mL 50 mg/mL red
Tetracycline HCL Tet 50 ug/mL 50 mg/mL in 100% ethanol yellow

These directions are not correct yet. Antibiotic stocks based on dH20 should to be filter-sterilized prior to use.

  1. add less than 5mL of dH20 to the 5mL falcon tube(s).
  2. multiply the mg of antibiotic listed in the stock column by 5 and add it to the dH20 in the falcon tube.
  3. dilute the solution to 5mL.
  4. filter sterilize if not using an antibiotic that is dissolved in ethanol.
    1. inst. on how to filter sterilize.
  5. using a P1000, pipette 5 1mL aliquots from the falcon tube into 5 microcentrifuge tubes; store at -20C.


  • Store all the aliquots at -20C.
  • Tet is light-sensative, so be sure to prevent exposure (i.e. wrap it in tinfoil or keep it in a dark box)
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