Assay :
Weigh and powder 20 tablets. Carry out the method for liquid chromatography, using the following solutions.
(1) Add 58 mL of methanol to a quantity of the powder containing 5 mg of Prednisolone, shake for 10 minutes, add sufficient water to produce 100 mL, mix and filter.
(2) Prepare solution (2) in the same manner as solution (1) but add 10 mL of a 0.075% w/v solution of dexamethasone (internal standard) in methanol and 48 mL of methanol in place of the 58 mL of methanol.
(3) 0.005% w/v of prednisolone ws and 0.0075% w/v of dexamethasone (internal standard) in a mixture of 58 volumes of methanol and 42 volumes of water.
CHROMATOGRAPHIC CONDITIONS
(a) Use a stainless steel column (20 cm × 4.6 mm) packed with octadecylsilyl silica gel for chromatography (5 µm) (Spherisorb ODS 1 is suitable).
(b) Use isocratic elution and the mobile phase described below.
(c) Use a flow rate of 1 mL per minute.
(d) Use an ambient column temperature.
(e) Use a detection wavelength of 254 nm.
(f) Inject 20 µL of each solution.
MOBILE PHASE
42 volumes of water and 58 volumes of methanol.
SYSTEM SUITABILITY
The assay is not valid unless, in the chromatogram obtained with solution (3), the resolution factor between the peaks due to prednisolone and dexamethasone is greater than 2.5 and the column efficiency, determined using the peak due to prednisolone, is greater than 15,000 theoretical plates per metre.
DETERMINATION OF CONTENT
Calculate the content of C21H28O5 in the tablets using the declared content of C21H28O5 in prednisolone ws.
Calculation :
