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Improved Quinine Impurity Method
Separation from dihydroquinine without ion-pair agents
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printable Application Sheet
Notes:
Quinine is an alkaloid found naturally in the bark of cinchona trees. It has been known for hundreds of years as an antimalarial agent
and a muscle relaxant. The Quechua inhabitants of Peru would grind the bark of cinchona trees and mix it with sweetened water to reduce
shivering in cold temperatures. Jesuits in Peru brought the bark to Europe where it was widely used to treat malaria and became known as
“Jesuit’s bark.”
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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 |
A: DI H2O/ 0.1% TFA
B: Acetonitrile/ 0.1% TFA |
| Gradient |
| time (min.) |
%B |
| 0 |
10 |
| 6 |
30 |
| 7 |
10 |
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| Post Time |
1 min. |
| Temperature |
40° C |
| Flow rate |
1.0 mL/min |
| Injection Volume |
10 µL |
| Sample |
Stock Solution: 1.0 mg quinine (90% by label claim) was dissolved in 1 mL 50% solvent A/50% solvent B mixture.
Working Solution: A 100 µL aliquot of the stock was diluted with 900 µL of 50% solvent A/50% solvent B mixture. |
| Peaks |
1. Minor impurity
2. Quinine (API)
3. Dihydroquinine (main impurity) |
| Detection |
UV 235 nm |
| t0 |
0.9 min |
Discussion
The USP method for quinine sulfate requires a resolution of not less than 1.2 from its main impurity, dihydroquinine. In the USP method, the ion
pair agents methanesulfonic acid and diethylamine are used in the mobile phase. Ion pair agents are often needed to reduce peak tailing of basic
analytes such as quinine when conventional type B silica-based HPLC columns are used. In this method, quinine is separated from its main impurity
with a resolution of 2.6 using only 0.1% TFA in the mobile phase. Using the Phenyl Hydride&153; column, excellent peak shapes were obtained for
both analytes. In addition, the method equilibrates rapidly with only 1 minute post time after the gradient and the column shows extended
lifetimes.
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