Determined by liquid chromatography.
Solvent mixture: 40 volumes of acetonitrile, 40 volume of methanol and 20 volumes of a buffer solution prepared by dissolving 2.0 gm of ammonium dihydrogen phosphate, in 1000ml
of water, adjusted to pH 3.0 with 10 per cent w/v solution of othophosphoric acid.
Test solution: Weigh and powder 20 tablets. Weigh accurately a quantity of the powder containing about 100mg Cilnidipine, disperse in 50ml solvent mixture with the aid of ultrasound for 15 minutes and dilute to 100ml with solvent mixture and filter. Dilute 5ml of the filtration to 100ml with the solvent mixture.
Reference solution: A 0.005 per cent w/v solution of cilnidipine reference standard in the solvent mixture.
Chromatographic system:
- A stainless steel column 15cm X4.6mm, packed with octadecylsilane bonded to porous silica (5µm) ( such as YMC ODS-AM),
- Mobile phase: a mixture of 25 volumes of a buffer solution prepared by dissolving 20 g of ammonium dihydrogen phosphate in 1000ml of water, adjusted to pH 30 with dilute O.P.A. and 75 volumes of methanol
- Flow rate: 1ml per minute,
- Spectrophotometer set at 245nm,
- Injection volume: 10µl
- Column temperature: 40°
Inject the reference solution. The test is not valid unless the column efficiency is not less than 2000 theoretical plates and the tailing factor is not more than 2.0 and the relative standard deviation for replicate injections is not more than 2.0 per cent.
Inject the reference solution and the test solution.
Calculate the content of Cilnidipine in the tablets.
Alternative Method: By UV Spectrophotometer
Test Solution: Weigh and powder 20 tablets. Weight sample equivalent to 25mg of Cilnidipine 100ml volumetric flask add 20ml methanol into it and sonicate to dissolve the test sample. Make up to mark with methanol. Filter and dilute 2ml of this solution to 50ml in same solvent.
Reference Solution: Weigh 25mg of reference standard of Cilnidipine in 100ml of volumetric flask. Add 20ml methanol into it and sonicate to dissolve. Dilute 2ml of this solution to 50ml with methanol.
Check Absorbance of test as well as reference standard at about 240nm in UV Spectrophotometer.
Calculate the content of Cilnidipine in the tablets.
Formula:
Abs. of Test STD Wt.(mg) 2 100 50 Potency
—————–X————–X——-X—————X——–X———–X Average wt.
Abs. of STD 100 50 Test Wt.(mg) 2 100
Acceptance criteria: 90.0%-110.0%
