A: It meets the requirements of Identificationtest Cunder Hypromellose.

B: Heat 5mLof Ophthalmic Solution in a test tube over a low flame:the warm solution turns cloudy but clears upon chilling.

Standard preparation— Dissolve a suitable quantity of USP Hydroxypropyl Methylcellulose RS,accurately weighed,in water,and dilute quantitatively with water to obtain a solution having a known concentration of about 100µg per mL.

Assay preparation— Dilute an accurately measured volume of Ophthalmic Solution quantitatively with water to obtain a solution having an equivalent concentration of about 100µg of hypromellose per mL.

Procedure— Pipet 2mLeach of the Standard preparation,the Assay preparation,and water to provide a blank,into separate,glass-stoppered test tubes.To each tube add 5.0mLof diphenylamine solution (prepared by dissolving 3.75g of colorless diphenylamine crystals in 150mLof glacial acetic acid and diluting the solution with 90mLof hydrochloric acid),mix,and immediately insert the tubes into an oil bath at 105to 110for 30minutes,the temperature being kept uniform within 0.1during heating.Remove the tubes,and place them in an ice-water bath for 10minutes or until thoroughly cool.At room temperature and using a suitable spectrophotometer,concomitantly determine the absorbances of the solutions from the Standard preparationand the Assay preparationat 635nm,using the water solution as the blank.Calculate the quantity,in mg,of hypromellose in each mLof the Ophthalmic Solution taken by the formula: in which Cis the concentration,in µg per mL,of USP Hydroxypropyl Methylcellulose RSin the Standard preparation;Vis the volume,in mL,of Ophthalmic Solution taken;dis the dilution fold of Vused to obtain the Assay preparation;and AUand ASare the absorbances of the solutions from the Assay preparationand the Standard preparation,respectively.