Ampicillin 100 mg/mL (1000X) recipe
Antibiotic stock for selecting E. coli carrying amp-resistance plasmids; use 1:1000 (100 µg/mL) in media and plates.
🧮 Volume calculator
| Component | Amount | Final concentration (1X) |
|---|---|---|
| Ampicillin sodium salt | 1 g | 100 mg/mL |
| Water (distilled) | to final volume |
Steps
- Dissolve in water and bring to volume.
- Filter-sterilise through 0.22 µm. Aliquot and store at −20 °C.
- Add 1 mL per litre (1000X): 100 µg/mL final.
Good to know
- Ampicillin degrades in media, causing satellite colonies — use plates within a month.
- The more stable carbenicillin (same concentration) is a common substitute.
FAQ
What are satellite colonies?
Tiny plasmid-free colonies growing where secreted β-lactamase has destroyed the ampicillin around a real colony. Avoid over-incubation.
This is a widely used standard composition. Amounts depend on the hydrate form and purity of your reagents — check the formula weight (FW) on the bottle and follow your institution's safety rules and the manufacturers' instructions.