Spectrophotometric Study on Determination of Aripiprazole in Tablets by Charge-Transfer and Ion-Pair Complexation Reactions with Some Acceptors

Two accurate, simple and sensitive spectrophotometric methods have been described for the assay of aripiprazole either in bulk substances or in tablets. The first method was based on the charge-transfer reaction of the drug as an nelectron donor with either 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) as π-acceptor or iodine (I₂) as σ-acceptor to give highly colored complexes. The absorbance of products was measured at 457 nm in acetonitrile and 364 nm in 1,2-dichloroethane for DDQ and I₂ methods, respectively. The second method was based on the formation of ion-pair complexes with the acidic sulphonephthalein dyes bromocresol green (BCG) and bromocresol purple (BCP). The color absorbance was measured at 413 and 400 nm in 1,2-dichloroethane for BCG and BCP, respectively. Under the optimum reaction conditions, Beer's law was obeyed with good correlation coefficients (r= 0.9997-0.9999) in the concentration ranges 10-120, 2-28, 2-24 and 2-20 μg mL^-1 of drug for DDQ, I₂, BCG and BCP methods, respectively. Spectral characteristics and stability constants of the formed ion associates are discussed in terms of the nature of donor and acceptor molecular structures. The proposed methods were successfully applied for determination of the drug in tablets with good accuracy and precision.