pH7.4Sodium phosphate buffer— Prepare as directed in the Assayunder Cromolyn Sodium.

Assay preparation— Remove and accurately weigh the contents of not fewer than 20capsules of Cromolyn Sodium Inhalation Powder,and transfer the combined contents to a 250-mLvolumetric flask.Dissolve in 100mLof water,dilute with water to volume,and mix.Transfer an aliquot of this solution,equivalent to 8mg of cromolyn sodium,to a 250-mLvolumetric flask,add 1mLof pH7.4Sodium phosphate buffer,dilute with water to volume,and mix.

Standard preparation— Dissolve a suitable quantity of USP Cromolyn Sodium RS,previously dried in vacuum at 105to constant weight and accurately weighed,in water to obtain a solution having a known concentration of about 350µg per mL.Transfer 10mLof this solution to a 100-mLvolumetric flask,add 1mLof pH7.4Sodium phosphate buffer,dilute with water to volume,and mix.The final concentration is about 35µg per mL.

Procedure— Concomitantly determine the absorbances of the Standard preparationand the Assay preparationin 1-cm cells at the wavelength of maximum absorbance at about 326nm,with a suitable spectrophotometer,using a solution of pH7.4Sodium phosphate buffer(1in 250)as the blank.Calculate the quantity,in mg,of cromolyn sodium (C23H14Na2O11)in the aliquot taken by the formula: in which Cis the concentration,in µg per mL,of USP Cromolyn Sodium RSin the Standard preparation;and AUand ASare the absorbances of the Assay preparationand the Standard preparation,respectively.