A9393 Sigma-Aldrich


anhydrous, 96.0-102.0% (anhydrous basis)

Synonym: D-(−)-α-Aminobenzylpenicillin

  • CAS Number 69-53-4

  • Empirical Formula (Hill Notation) C16H19N3O4S

  • Molecular Weight 349.40

  •  Beilstein/REAXYS Number 1090925

  •  EC Number 200-709-7

  •  MDL number MFCD00005175

  •  PubChem Substance ID 24891442

  •  NACRES NA.85



Related Categories A - K, Antibacterial, Antibiotics, Antibiotics A to Z, Antibiotics by Application,
assay   96.0-102.0% (anhydrous basis)
form   solid
pKa (25 °C)   2.5 (COOH)
  7.3 (NH2)
mp   208 °C (dec.) (lit.)
Mode of action   cell wall synthesis | interferes
antibiotic activity spectrum   Gram-negative bacteria
  Gram-positive bacteria
storage temp.   2-8°C


General description

Chemical structure: ß-lactam


Ampicillin has been used to study antibiotic resistance and penetration limitations, the synergy between multiple antibiotics, certain bloodstream infections, and has been used to develop PCR assays to detect resistance genes in cerebrospinal fluid.

Biochem/physiol Actions

β-lactams are inactivated by β-lactamases and for this reason ampicillin is used with a β-lactamase inhibitor.

Mode of Action: Ampicillin is a semisynthetic penicillin and a ß-lactam antibiotic that inhibits bacterial cell-wall synthesis by inactivating transpeptidases on the inner surface of the bacterial cell membrane.

Mode of Resistance: Administration with ß-lactamase cleaves the ß-lactam ring of Ampicillin and inactivates it.

Antimicrobial Spectrum: Effective against both Gram-positive (similar to benzylpenicillin) and Gram-negative bacteria (similar to tetracyclines and chloramphenicol.


This product has been reported stable as supplied at 25°C at 43% and 81% relative humidity for six weeks. Additional studies have shown that the stability of Ampicillin in solution is a function of pH, temperature and the identity of the buffer. It′s activity is quickly lost when stored above pH 7. Optimal storage conditions are suggested as 2-8°C, and pH 3.8-5 where its activity was retained at 90%+ for a week.

Preparation Note

Ampicillin is reported as slightly soluble in water, practically insoluble in alcohol, chloroform, ether and fixed oils but soluble in dilute acids or bases. The solution should not be autoclaved; a stock solution should be sterilized through filtration and stored frozen, where it will be stable for months.

Other Notes

Store under argon. Keep container tightly closed in a dry and well-ventilated place, hygroscopic.

Safety & Documentation

Safety Information

Signal word 
Hazard statements 
Precautionary statements 
Personal Protective Equipment 
NONH for all modes of transport
WGK Germany 


Certificate of Analysis (COA)

Please Enter a Lot Number

Certificate of Origin (COO)

Please Enter a Lot Number

Frequently Asked Questions

Which document(s) contains shelf-life or expiration date information for a given product?
If available for a given product, the recommended re-test date or the expiration date can be found on the Certificate of Analysis.
IsAmpicillin product stable in solution?
We recommend using freshly prepared solutions. A concentrated solution of sodium ampicillin in water (approximately 330 mg/mL) may be expected to lose about 10% potency in 20 hours at -20°C.
How do I useAmpicllin in agar plates?
For plates, add ampicillin to autoclaved media cooled to 48°C, to a final concentration of 35-50 μg/mL. Pour the plates, and allow them to cool completely. Plates may be stored at 2-8°C for up to only 1-2 weeks before use.
How do I get lot-specific information or a Certificate of Analysis?
The lot specific COA document can be found by entering the lot number above under the "Documents" section.
What is the solubility of Product A9393, Ampicillin?
The solubility of ampicillin is tested at 50 mg/mL in 1M ammonium hydroxide. Additional solubility information can be found on the product information sheet (under Documents, above).
Which Ampicillin product has higher water solubility, Product A9393 or Product A9518?
Product No. A9518 (Ampicillin, sodium salt) is soluble at 50 mg/mL in water.
How do I find price and availability?
There are several ways to find pricing and availability for our products.Once you log onto our website, you will find the price and availability displayed on the product detail page.You can contact any of our Customer Sales and Service offices to receive a quote. USA customers: 1-800-325-3010 orview local office numbers.
What is the Department of Transportation shipping information for this product?
Transportation information can be found in Section 14 of the product's (M)SDS.To access the shipping information for this material, use the link on the product detail page for the product.
My question is not addressed here, how can I contact Technical Service for assistance?
Ask a Scientist here.
Show more questions
Protocols & Articles
Peer-Reviewed Papers


Related Products

related product

Product #


Add to Cart

08168 Timestrip Plus 8 °C

Technical Service:

Our team of scientists has experience in all areas of research including Life Science, Material Science, Chemical Synthesis, Chromatography, Analytical and many others.

Bulk Ordering & Pricing:

Need larger quantities for your development, manufacturing or research applications?