Semautomated method for the analysis of chlorpheniramine maleate tablets: collaborative study.

A semautomated method for the analysis of chlorpheniramine maleate tablets, which is based on the USP XIX general assay for salts of organic nitrogenous bases, was collaboratively studied by 6 laboratories. Collaborators were supplied with 4 composites from 4 manufacturers. In the method, the active ingredient is dissolved in dilute HCl, sampled, made basic with dilute NaOH, and extracted with isooctane. The isooctane phase is resampled and the drug is re-extracted into dilute HCl. The absorbance of the acidic aqueous solution is measured at 265 nm. The Associate Referee assayed the collaborative samples to compare the semiautomated and USP XIX methods, and found close agreement in the results from the 2 methods. In the collaborative study of the semiautomated method, there was excellent agreement of the results obtained by the collaborators. The coefficients of variation ranged from 0.46 to 2.24%. The method has been adopted as official first action.