Abstract
The proposed method for combinations of antihistamines with phenylephrine.HCl uses three columns, HC1, NaOH, and H2SO4. Chlorpheniramine and codeine are removed from the columns with a chloroform solution of triethylamine. The chloroform eluates are evaporated and the residues taken up in dilute HCl. They are determined spectrophotometrically by comparison with the appropriate standard solutions. The phenylephrine is acetylated on the column with a chloroform solution of acetic anhydride. The acetylphenylephrine is then eluted with chloroform, and the solvent is evaporated and saponified with alcoholic-KOH. The reformed phenylephrine can then be determined spectrophotometrically in either an acid or alkaline aqueous solution and compared to the appropriate standard solution. The results of eight collaborators and the Associate Referee give the following average recoveries in the assay of an authentic elixir: codeine, 100.3%; phenylephrine.HCl, 97.4%; and chlorpheniramine maleate, 102.5%. The method was adopted as official, first action.
UHPLC assay and impurity methods for diphenhydramine and phenylephrine hydrochloride oral solution