Because of the similarity of nifedipine and dihydronifedipine structure, it is very difficult to assay each compound in the mixture of two ones. I only find one difference between two compounds. That is oxidation - reduction ability. So can I use it for determination? If yes, which reagents should I use?
Dissolve 0.1300 g in a mixture of 25 ml of 2-methyl-2-propanol R and 25 ml of perchloric acid solution R. Titrate with 0.1 M cerium sulphate using 0.1 ml of ferroin R as indicator, until the pink colour disappears. Titrate slowly towards the end of the titration. Carry out a blank titration.
1 ml of 0.1 M cerium sulphate is equivalent to 17.32 mg of C17H18N2O6.
Dear Nguyen,
Have you thought of using HPLC coupled to an electrochemical detector?
These are very simple methods and extremely economical to operate.
The nitro group is amenable to negative potential work at the picogram level eg at the pendant drop mercury electrode (as pioneered by John BF Lloyd in the UK eg J. Forensic Science, 1990, 35(4) 956-959).
The dihydropyridine ring may be amenable to positive potential solid electrode electrochemical detection which is much easier to operate as long as you apply some clean up to your samples before analysis. (To keep the electrode surface from contamination).
I know this technique has been used for many years in forensic's for morphine determination in blood. (Author was Mike White in J. Chrmoatography).(latest Wen-Jinn Liaw, J Chromatography B, 1998, 714, (2), 237-245.)
The HPLC techniques are usually easily operated in a pharmaceutical type environment ,and if you are lucky, are so reproducible that the internal standard method is not required.
Detectors are I believe commercially available.
Hope this is helpful,
Kind regards,
Dr John
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