Validated Spectrophotometric Method for Determination of Escitalopram Through Study of Charge Transfer and Ion Pair Complexation

Two simple and sensitive spectrophotometric methods were developed and validated for quantitative determination of escitalopram(Esc). The first method is based on the formation of charge-transfer complexes between the drug as n-donor and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), 7,7,8,8-tetracyanoquinodimethane (TCNQ), tetracyanoethylene (TCNE) and p -chloranilic acid ( p -CA) as I€ -acceptors to give highly colored complex species. The products exhibit absorption maxima at 456, 841, 413 and 518 nm in acetonitrile for DDQ, TCNQ, TCNE and p -CA, respectively. Beer’s law was obeyed in the range of 8.28–373.00 I¼g mL -1 . Moreover Kinetic spectrophotometry was adopted for analysis of Esc with TCNE, using initial rate and fixed time methods. The second method is based on the formation of yellow ion-pair complexes between escitalopram and four sulphonphthalein acid dyes, namely; bromocresol purple (BCP), bromophenol blue (BPB), bromocresol blue (BCB), and bromocresol green (BCG) in chloroform. The formed complexes are measured at 407, 413, 415 and 416 nm for BCP, BPB, BCB and BCG, respectively. Under the optimum reaction conditions, linear relationships with good correlation coefficients (0.9996 - 0.9999) are found between absorbance of the formed complexes and concentrations of escitalopram in the range of 2.07–41.44 I¼g mL -1 . Spectral characteristics and stability constants of the formed ion associates are discussed in terms of the nature of donor and acceptor molecular structures. The molar absorptivities and association constants for the colored complexes were evaluated using the Benesi-Hildebrand equation. The proposed methods were successfully applied for determination of the drug in tablets with good accuracy and precision. Â