Determined by liquid chromatography.
Test solution: Weigh and powder 20 tablets. Shake a quantity of the powder containing 20mg of terbinafine with 50ml of the mobile phase and mix with the aid of ultrasound for 20 minutes, dilute to 100ml with the mobile phase and filter.
Reference solution: A 0.022 per cent w/v solution of terbinafine HCl reference solution in the mobile phase.
Chromatographic system:
- A stainless steel column 15cm X 3.9mm, packed with octaysilane bonded to porous silica(5µm),
- Mobile phase: 60 volumes of a buffer solution prepared by dissolving 0.85g of monobasic potassium phosphate and 1.0 g of sodium 1-decanesulfonate in 1000ml of water and adjusted to pH 3.0 with O.P.A. and 40 volumes of acetonitrile,
- Flow rate: 1.8ml per minute,
- Spectrophotometer set at 220nm,
- Injection volume: 5µl
Inject the reference solution. The test is not valid unless 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 Terbinafine in the tablets.
Alternative Method: By UV Spectrophotometer
Test Solution: Weigh and powder 20 tablets. Weight sample equivalent to 50mg of Terbinafine 100ml volumetric flask add 20ml methanol into it and sonicate to dissolve the test sample. Make up to mark with 0.1M HCl. Filter and dilute 1ml of this solution to 50ml in 0.1 M HCl.
Reference Solution: Weigh 50mg of reference standard of Terbinafine HCl in 100ml of volumetric flask. Add 20ml methanol into it and sonicate to dissolve. Make up to mark with 0.1M HCl. Dilute 1ml of this solution to 50ml with 0.1 M HCl.
Check Absorbance of test as well as reference standard at about 283nm in UV Spectrophotometer.
Calculate the content of Terbinafine in the tablets.
Formula:
Area of Test STD Wt. (mg) 1 100 50 Potency
—————–X——————-X———X—————X———-X————–X Average wt.
Area of STD 100 50 Test Wt. (mg) 1 100
Acceptance criteria: 90.0%-110.0%
