Problem in the analysis of sodium valproate
Posted: Sat Mar 26, 2005 6:15 pm
Dear members of this forum,
I need your opinions in order to solve an analytical problem. I am working with the dissolution test of sodium valproate tablets and my problem is chromatographic purely not the dissolution method.
In the test, the solution test is 0.002 % w/v, the volume injected is 50 uL, the wavelength of measuring is 220 nm and the solvent is buffer pH 6.8 (the mobile phase is 60 % buffer pH 6.8 and 40 % acetonitrile). In this conditions the area was very small and I have to change the conditions in order to increase the area and I reach about 300 mAu*min with a symmetry factor of about 0.75 when the European pharmacopoeia limit is 0.8.
The conditions of working was 100 uL, 210 nm and the concentration was 200 mg/L. In my opinion the fronting is owing to a high concentration injected but the drug had a very low absorbance. The initial test is a British pharmacopoeia method which I had to change. I worked with a diluent less strong than the mobile phase which minimize the overlad (buffer pH 6.
. The original column uBondapack C18 and I worked with Lichrospher C18 but the particle size is 5 um in both columns.
I will appreciate your opinions in order to get better results, Thanks in advance for your help,
Diego
I need your opinions in order to solve an analytical problem. I am working with the dissolution test of sodium valproate tablets and my problem is chromatographic purely not the dissolution method.
In the test, the solution test is 0.002 % w/v, the volume injected is 50 uL, the wavelength of measuring is 220 nm and the solvent is buffer pH 6.8 (the mobile phase is 60 % buffer pH 6.8 and 40 % acetonitrile). In this conditions the area was very small and I have to change the conditions in order to increase the area and I reach about 300 mAu*min with a symmetry factor of about 0.75 when the European pharmacopoeia limit is 0.8.
The conditions of working was 100 uL, 210 nm and the concentration was 200 mg/L. In my opinion the fronting is owing to a high concentration injected but the drug had a very low absorbance. The initial test is a British pharmacopoeia method which I had to change. I worked with a diluent less strong than the mobile phase which minimize the overlad (buffer pH 6.
. The original column uBondapack C18 and I worked with Lichrospher C18 but the particle size is 5 um in both columns.I will appreciate your opinions in order to get better results, Thanks in advance for your help,
Diego