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Valsartan/Hydrochlorothiazide (HCT)
Improved gradient method with faster equilibration
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printable Application Sheet
Comparison of Bidentate C18™ method and USP method using an ordinary C18 Column
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Bidentate C18™ |
Type B C18 |
| Total run time |
10 min |
40 min |
| Column volumes for equilibration |
1 |
>10 |
| Solvent usage per run |
10 mL |
40 mL |
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Method Conditions
| Column |
Cogent Bidentate C18™, 4µm, 100A |
| Catalog No. |
40018-75P |
| Dimensions |
4.6 x 75 mm |
| Mobile Phase |
A: DI H2O + 0.1% TFA
B: Acetonitrile + 0.1% TFA |
| Gradient |
| time (min.) |
%B |
| 0 |
10 |
| 8 |
90 |
| 9 |
10 |
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| Post Time |
1 min |
| Flow Rate |
1.0 mL/min |
| Injection Vol. |
10 µL |
| Detection |
UV 265 nm |
| Sample |
Stock Solution: A Diovan HCT® tablet containing 160 mg valsartan and 25 mg hydrochlorothiazide was ground and added to a 50
mL volumetric flask. The flask was diluted to mark with 50/50 solvent A/solvent B mixture and sonicated. A portion was then filtered
with a 0.45 micron nylon syringe filter AQ™ Brand (MicroSolv Tech Corp).
Working Solution: 100 µL of the stock solution was diluted with 900 µL of a 50/50 solvent A/solvent B mixture. |
| t0 |
1 min |
Discussion
The USP assay method for valsartan in combination with hydrochlorothiazide features a 27 minute gradient with a 13 minute reequilibration for
a total run time of 40 minutes. Because the Bidentate C18™ column is based on a TYPE-C Silica™ surface, it is much less hydrophilic
than ordinary HPLC columns and therefore equilibrates much faster when gradients are used. In this method, the run time was a quarter of the USP
method, demonstrating a substantial time and solvent savings for the analytical laboratory. Diovan® is marketed by Novartis and is under
patent protection in the U.S. until 2012.
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