(Ph. Eur. 11.6 update)
Action and use
Beta-adrenoceptor antagonist.
DEFINITION
Betaxolol Eye Drops, Solution are a sterile solution of Betaxolol Hydrochloride in Purified Water.
The eye drops comply with the requirements stated under Eye Preparations and with the following requirements.
Content of betaxolol, C18H29NO3
90.0 to 110.0% of the stated amount.
IDENTIFICATION
A. Carry out the method for thin-layer chromatography, Appendix III A, using the following solutions.
(1) Dilute the eye drops with water to produce a solution containing the equivalent of 0.1% w/v of betaxolol. Shake 1 mL of the solution with 4 mL of water, 0.1 mL of 13.5M ammonia and 2 mL of chloroform, centrifuge and use the chloroform layer.
(2) Prepare solution (2) in the same manner as solution (1) but using a 0.1% w/v solution of betaxolol hydrochloride BPCRS in place of the eye drops.
(3) A mixture of equal volumes of solution (1) and solution (2).
CHROMATOGRAPHIC CONDITIONS
(a) Use as the coating silica gel (Merck silica gel 60 plates are suitable).
(b) Use the mobile phase as described below.
(c) Apply 5 μL of each solution.
(d) Develop the plate to 15 cm.
(e) After removal of the plate, dry in air, spray with a solution prepared by dissolving 5 g of iodine and 10 g of potassium iodide in sufficient water to produce 100 mL and mixing 20 mL of the resulting solution with 30 mL of water and 50 mL of 2M acetic acid. Examine the plate immediately; spots due to betaxolol appear brown.
MOBILE PHASE
30 volumes of a solution prepared by diluting 1 volume of 13.5M ammonia to 50 volumes with propan-2-ol immediately before use and 70 volumes of chloroform.
SYSTEM SUITABILITY
The test is not valid unless the chromatogram obtained with solution (3) shows a single, compact spot.
CONFIRMATION
The principal spot in the chromatogram obtained with solution (1) corresponds in position and colour to that in the chromatogram obtained with solution (2).
B. In the Assay, the chromatogram obtained with solution (1) shows a principal peak with the same retention time as the principal peak in the chromatogram obtained with solution (2).
TESTS
Acidity or alkalinity
pH, 6.0 to 7.8, Appendix V L.
Related substances
Carry out the method for liquid chromatography, Appendix III D, using the following solutions in the mobile phase.
(1) Dilute a suitable volume of the eye drops to produce a solution containing the equivalent of 0.02% w/v of betaxolol.
(2) Dilute 1 volume of solution (1) to 100 volumes.
CHROMATOGRAPHIC CONDITIONS
(a) Use a stainless steel column (25 cm × 4.6 mm) packed with octadecylsilyl silica gel for chromatography (10 μm) (Spherisorb ODS-2 is suitable).
(b) Use isocratic elution and the mobile phase described below.
(c) Use a flow rate of 1.5 mL per minute.
(d) Use an ambient column temperature.
(e) Use a detection wavelength of 220 nm.
(f) Inject 20 μL of each solution.
MOBILE PHASE
Dissolve 3 g of sodium dodecyl sulfate in 450 mL of the following solution. 45 volumes of a buffer solution prepared as described below and 55 volumes of acetonitrile. To prepare the buffer solution add 5 mL of orthophosphoric acid to 990 mL of water, adjust the pH to 3.0 with 2M ammonia and add sufficient water to produce 1000 mL.
SYSTEM SUITABILITY
The test is not valid unless, in the chromatogram obtained with solution (2), the column efficiency, determined on the peak due to betaxolol is at least 8000 theoretical plates per metre and the symmetry factor of the principal peak is not more than 2.5.
LIMITS
In the chromatogram obtained with solution (1):
the area of any secondary peak is not greater than the area of the principal peak in the chromatogram obtained with solution (2) (1%);
the area of not more than one secondary peak is greater than 0.3 times the area of the principal peak in the chromatogram obtained with solution (2) (0.3%).
ASSAY
Carry out the method for liquid chromatography, Appendix III D, using the following solutions in the mobile phase.
(1) Dilute the eye drops to produce a solution containing the equivalent of 0.01% w/v of betaxolol.
(2) 0.012% w/v of betaxolol hydrochloride BPCRS.
CHROMATOGRAPHIC CONDITIONS
(a) Use a stainless steel column (25 cm × 4.6 mm) packed with octadecylsilyl silica gel for chromatography (10 μm) (Spherisorb ODS-2 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 220 nm.
(f) Inject 10 μL of each solution.
MOBILE PHASE
45 volumes of acetonitrile and 55 volumes of water containing 0.71% w/v of anhydrous disodium hydrogen orthophosphate and 0.91% w/v of dimethylamine hydrochloride, adjusted to pH 3.0 with orthophosphoric acid.
DETERMINATION OF CONTENT
Calculate the content of C18H29NO3 in the eye drops using the declared content of C18H29NO3 in betaxolol hydrochloride BPCRS.
STORAGE
Betaxolol Eye Drops, Solution should be protected from light.
LABELLING
The quantity of active ingredient is stated in terms of the equivalent amount of betaxolol.
