Three simple, sensitive and accurate spectrophotometric methods have been developed for the determination of dextromethorphan hydrobromide (DEX) and ketamine hydrochloride (KET) in dosage forms. These methods are based on the formation of ion-pair complexes with bromocresol green (BCG), bromocresol purple (BCP), and bromophenol blue (BPB) in acidic medium. The coloured ion-pair products are measured at 419, 409 and 417 nm for DEX and at 417, 408 and 416 nm for KET using BCG, BCP and BPB, respectively. Beer’s law was obeyed in the range of 2.0-22 μg mL-1 for DEX and 2.0-16 μg mL-1 for KET. The composition of the ion-pair was established by continuous variation and molar ratio methods. The proposed methods were applied successfully for the determination of DEX and KET in dosage forms applying the standard addition technique and compared statistically with the official methods. The molar absorptivity, Sandell sensitivity, detection and quantification limits were also calculated.
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