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Fexofenadine
Simple Isocratic Assay Method without Amine Additives
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printable Application Sheet
Notes:
Fexofenadine is marketed under the trade name Allegra®, but generic versions are also available. In January 2011, the Food and Drug
Administration approved over-the-counter sales of the drug without a prescription. It is a widely selling antihistamine used for treatment
of hay fever and other allergies. Because it does not cross the blood-brain barrier, it causes less drowsiness than first generation
antihistamines.
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Method Conditions
| Column |
Cogent Phenyl Hydride™, 4µm, 100A |
| Catalog No. |
69020-7.5P |
| Dimensions |
4.6 x 75 mm |
| Mobile Phase |
62% DI water/ 38% Acetonitrile/ 0.1% TFA |
| Temperature |
35° C |
| Flow rate |
1.0 mL/min |
| Injection Volume |
5 µL |
| Sample |
Stock Solution: 180 mg strength Allegra® tablet was ground and added to a 100 mL volumetric flask. It was diluted with the
mobile phase and vortexed 5 min. A portion was filtered with a 0.45 micron nylon syringe filter (MicroSolv Tech Corp).
Working Solution: A 100 µL aliquot of the stock was diluted with 900 µL of the mobile phase. |
| Peaks |
Fexofenadine |
| Detection |
UV 220 nm |
| t0 |
0.87 min |
Discussion
Fexofenadine is well-suited for retention with the Phenyl Hydride column since it has a number of aromatic moieties. Also, the tertiary amine can cause
peak tailing issues with type B silica-based L11 columns if an amine additive is not used in the mobile phase. The USP assay method for fexofenadine
tablets uses triethylamine for this reason. Here, excellent peak shapes are observed from the five-run overlay shown in the figure using only
triflouroacetic acid as the mobile phase additive.
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