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Amoxicillin
Orthogonal retention method to USP assay
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printable Application Sheet
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Notes: Amoxicillin is a beta-lactam antibiotic used to treat a variety of bacterial infections. Its mechanism of action is by inhibition of the
synthesis of bacterial cell walls.
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Method Conditions
| Column |
Cogent Diamond Hydride™, 4µm, 100A |
| Catalog No. |
70000-7.5P |
| Dimensions |
4.6 x 75 mm |
| Solvents |
| A: | DI water + 10 mM amonium acetate |
| B: | 90% Acetonitrile/ 10% DI water/ 10 mM ammonium acetate |
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| Gradient |
| time (min.) |
%B |
| 0 |
100 |
| 4 |
90 |
| 5 |
100 |
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| Injection Vol. |
2 microL |
| Flow rate |
1.0 mL/min. |
| Detection |
UV 230 nm |
| Sample |
Stock Solution: 1 mg/mL amoxicillin trihydrate USP RS in 50/50 A/B diluent.
Working Solution: A 100 µL aliquot of the stock was diluted to 0.1 mg/mL using 900 µL 50/50 A/B diluent. |
| Peak |
Amoxicillin |
| t0 |
0.95 min. |
Discussion
The USP assay method for amoxicillin is performed in reversed phase. Analysis by an orthogonal retention mode is very useful and can be readily done by
aqueous normal phase (ANP) using solvents common to both retention modes. A benefit of the ANP method is the more symmetrical peak shape obtained.
This is important for compounds such as amoxicillin that can give poor peak shapes in reversed phase.
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