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Lamotrigine, A Very Polar Compound
USP Assay Method
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printable Application Sheet
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Note: Lamotrigine is a phenyltriazine anticonvulsant used to treat epilepsy and type I bipolar disorder. It is believed to act as a
sodium channel blocker.
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Method Conditions
| Column |
Cogent Bidentate C18™, 4µm, 100A |
| Catalog No. |
40018-15P |
| Dimensions |
4.6 x 150 mm |
| Solvents |
A: 2.7 g/L KH2PO4: triethylamine 150:1, adjusted to
pH 2.0 with H3PO4
B: acetonitrile |
| Gradient |
| time (min.) |
%B |
| 0 |
23.5 |
| 4 |
23.5 |
| 14 |
80 |
| 15 |
23.5 |
| 19 |
23.5 |
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| Injection Volume |
10 microL |
| Detection |
UV 270 nm |
| Sample |
25 mg strength tablet was ground and dissolved in 5
mL MeOH in a 100 mL volumetric flask. The flask
was diluted to mark with 0.10 M HCl. It was
sonicated and filtered with a 0.45 µm nylon filter
(MicroSolv Tech Corp). |
| Peak |
Lamotrigine |
| t0 |
1.9 min |
Discussion
The USP assay method for lamotrigine uses a relatively low pH of 2.0. These conditions may promote hydrolysis of the bonded phase in conventional
L1 columns, but the unique chemistry of the Cogent Bidentate C18™ column is very rugged and shows no loss of retention for the API, as the
five run overlay in the figure shows. The retention time %RSD for the five runs was 0.15%. In addition the peak shape was highly symmetrical.
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