Determined by liquid chromatography.

Reference solution (a). A 0.004 per cent w/v solution of ondansetron reference standard in 0.01 M hydrochloric acid.

Reference solution(b). A 0.014 per cent w/v solution of 3[Dimethylamino methyl]-1,2,3,9-tetrahdro-9-methyl-H-carbazol-4-one-RS (ondansetron impurity A reference standard) in 0.01 M HCl.

Reference solution(c). Transfer 8.0ml each of reference solution (a) and (b) to 50ml volumetric flask and dilute to volume with 0.01 M HCl.

Test solution: Weigh and powder 20 tablets. Disperse a quantity of powder containing about 40mg of ondansetron with about 60ml of 0.01 M hydrochloric with the aid of ultrasound for about 10 minutes and dilute 100.0ml. Filter through polypropylene membrane of 0.45 µm pore size. Discard first few ml of the filtrate. Dilute 1.0ml of the solution to 10.0ml with 0.01 M HCl.

           Chromatographic system:

  • A stainless steel column 25cm X4.6mm, packed with nitrile group bonded to porous silica (5µm)
  • Mobile Phase: a mixture of 52 volumes of 0.272 per cent w/v solution of monobasic potassium phosphate, adjusted to pH 5.4 with 1M sodium hydroxide and 48 volumes of acetonitrile,
  • Flow rate: 1.5ml per minute,
  • Spectrophotometer set at 216nm,
  • Injection volume: 10µl

The relative retention time with reference to ondansetron for ondansertron impurity A is about 1.1.

Inject reference solution (c). The test is not valid unless the resolution between the peaks due to ondansetron and ondansetron impurity A is not less than 1.5 and tailing factor is not more than 2.0 for ondansetron peak.

Inject reference solution(a) and the test solution.

Calculate the content of Ondansetron the tablet.

  Alternative Method: By UV Spectrophotometer

Reference Solution: Weigh 30mg of reference standard of Ondansetron HCl in 50ml of volumetric flask. Add 10ml of 0.1 M HCl into it and sonicate to dissolve. Dilute 1ml of this solution to 50ml with same solvent.

Test Solution: Weigh and powder 20 tablets. Weight sample equivalent to 5mg of Ondansetron in 100ml volumetric flask add 10ml 1.0 M HCl into it and sonicate to dissolve the test sample. Make up to mark with 0.1M HCl. Filter and dilute5ml of this solution to 25ml in same solvent.

            Check Absorbance of test as well as reference standard at 310nm in UV Spectrophotometer.

Calculate the content of Ondansetron.

Formula for calculation:

Absorbance of TEST       STD wt. (mg)             1                 100                25                   Potency

—————————-X——————–X———X—————-X———X——————X Avg. Wt.

Absorbance of STD            50                               50        Test wt (mg)      5                     100

           Acceptance criteria: 90.0%-110.0%

HPLC Method