A: Triturate a portion of the contents of Capsules,equivalent to about 100mg of guaifenesin,with 10mLof chloroform,filter,and evaporate 1mLof the filtrate on a watch glass.Mix the residue with 1drop of formaldehyde and a few drops of sulfuric acid:a deep cherry-red to purple color is produced.

B: The retention time of the guaifenesin peak in the chromatogram of the Assay preparationcorresponds to that of the guaifenesin peak in the chromatogram of the Standard preparationas obtained in the Assay.

Medium: water;900mL.

Apparatus 1: 100rpm.

Time: 45minutes.

Procedure— Determine the amount of C10H14O4dissolved,employing the procedure set forth in the Assay,making any necessary modifications.

Tolerances— Not less than 75%(Q)of the labeled amount of C10H14O4is dissolved in 45minutes.

Mobile phase,Benzoic acid solution,Resolution solution,Standard preparation,and Chromatographic system— Proceed as directed in the Assayunder Guaifenesin Tablets.

Assay preparation— Transfer,as completely as possible,the contents of not less than 20Capsules to a suitable tared container,and determine the average content weight per Capsule.Mix the combined contents,and transfer an accurately weighed portion,equivalent to about 200mg of guaifenesin,to a 100-mLvolumetric flask.Proceed as directed for Assay preparationin the Assayunder Guaifenesin Tablets,beginning with “add about 60mLof water.”

Procedure— Proceed as directed for Procedurein the Assayunder Guaifenesin Tablets.Calculate the quantity,in mg,of guaifenesin (C10H14O4)in the portion of Capsule contents taken by the formula: in which the terms are as defined therein.