Edition: BP 2025 (Ph. Eur. 11.6 update)
DEFINITION
Sodium Cromoglicate Eye Drops are a sterile solution of Sodium Cromoglicate in Purified Water.
The eye drops comply with the requirements stated under Eye Preparations and with the following requirements.
Content of sodium cromoglicate, C23H14Na2O11
95.0 to 105.0% of the stated amount.
IDENTIFICATION
A. The light absorption, Appendix II B, in the range 230 to 400 nm of a solution of the eye drops diluted to contain 0.002% w/v of Sodium Cromoglicate exhibits two maxima at 239 and 326 nm, and a shoulder at about 260 nm.
B. To 1 mL of the eye drops add 2.5 mL of 1M sodium hydroxide and boil for 1 minute; a yellow colour is produced. Add 0.5 mL of diazobenzenesulfonic acid solution; a deep red colour is produced.
TESTS
Acidity or alkalinity
pH, 4.0 to 7.0, Appendix V L.
Related substances
Carry out the method for thin-layer chromatography, Appendix III A, using a precoated silica gel F254 plate (Merck silica ge 60 F254 plates are suitable) and a mixture of 5 volumes of glacial acetic acid, 50 volumes of ethyl acetate and 50 volumes of toluene as the mobile phase but allowing the solvent front to ascend 10 cm above the line of application. Apply separately to the plate 5 µL of each of the following solutions. For solution (1) use the eye drops, diluted, if necessary wit water, to contain 2% w/v of Sodium Cromoglicate. Solution (2) contains 0.01% w/v of 1,3-bis(2-acetyl-3-hydroxyphenoxy ) -2-propanol in dichloromethane. After removal of the plate, allow it to dry in air and examine under ultraviolet light (254 nm). Any secondary spot in the chromatogram obtained with solution (1) is not more intense than the spot in the chromatogram obtained with solution (2) (0.5%).
ASSAY
Dilute the eye drops with phosphate buffer pH 7.4 to give a solution containing 0.004% w/v of Sodium Cromoglicate and measure the absorbance of the resulting solution at the maximum at 326 nm, Appendix II B. Calculate the content of C23H14Na2O11 in the eye drops taking 164 as the value of A(1%, 1 cm) at the maximum at 326 nm.
