Simultaneous semiautomated assay of pyrrobutamine phosphate, cyclopentamine hydrochloride, and methapyrilene hydrochloride in pharmaceutical mixtures.

Antihistamine preparations containing methapyrilene hydrochloride, pyrrobutamine phosphate, and cyclopentamine hydrochloride were assayed by introducing an aqueous sample solution into the appropriate automated system. Methapyrilene hydrochloride was determined by UV spectrophotometry. Pyrrobutamine phosphate was extracted as an ion-pair and quantitated colorimetrically by forming the bromcresol purple acid-dye complex. Cyclopentamine hydrochloride was determined colorimetrically by using the copper dithiocarbamate reaction for secondary amines.