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Forced Degradation of Atorvastatin (LC-MS)
Separation of API from its lactone degradation product
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printable Application Sheet
Tablet Stock Solution: A 40 mg strength tablet was ground and added to a 100 mL volumetric flask. A 50 mL portion of solvent B was added
to the flask. The solution was vortexed 5 min, sonicated 5 min, and diluted to mark with solvent A. It was then filtered through a 0.45 µm
nylon membrane (MicroSolv Technology Corp. Eatontown, NJ, USA).
Degraded Tablet Stock Solution: A 40 mg strength tablet was ground and added to a 100 mL volumetric flask. A 50 mL portion of solvent B
was added to the flask. It was then vortexed 5 min, sonicated 5 min, and diluted to mark with 3 M HCl. It was then filtered through a 0.45 #181;m
nylon membrane (MicroSolv Technology Corp. Eatontown, NJ, USA).
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Method Conditions
| Column |
Cogent Bidentate C18™, 4µm, 100A |
| Catalog No. |
40018-05P-2 |
| Dimensions |
2.1 x 50 mm |
| Solvents |
A: 50% DI water/ 50% methanol/ 10 mM ammonium acetate
B: 90% acetonitrile / 10% DI water / 10 mM ammonium acetate.
Both solutions were vacuum filtered through a 0.45 µm nylon filter (MicroSolv Technology Corp. Eatontown, NJ,
USA). |
| Gradient |
| time (min.) |
%B |
| 0 |
30 |
| 10 |
100 |
| 12 |
30 |
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| Flow rate |
0.4 mL/min |
| Detection |
ESI – POS - Agilent 6210 MSD TOF mass spectrometer |
| Sample |
Figure A: 10 µL tablet stock diluted with 990 µL 50:50 A:B.
Figure B and C: 10 µL degraded tablet stock diluted with 990 µL 50:50 A:B. |
| Peaks |
1. Atorvastatin, 2. Atorvastatin lactone |
Discussion
Atorvastatin is separated from its main degradation product using a Bidentate C18 column and a simple linear reversed phase gradient. With the use of
LC-MS, the identity of the degradant can be confirmed from its m/z value. The degradation is an intramolecular Fischer esterification, which is
catalyzed under acidic conditions. Figure A shows the extracted ion chromatogram (EIC) corresponding to atorvastatin for the non-degraded extract.
Figures B and C show the EICs of atorvastatin and the lactone degradant respectively for the acid-degraded extract. The atorvastatin lactone peak
observed in Figure C was found to be absent in the non-degraded extract. The method shows good retention of both compounds past the void volume (0.4
min) as well as excellent peak symmetry.
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