ABSTRACT
Simple and sensitive spectrophotometric methods were described for the determination of two drugs; namely, mianserin and risperidone, with n-donating groups. The methods were based mainly on charge transfer complexation reactions, with two acceptors 2,3-dichloro-5,6-dicyano benzoquinone [DDQ] and p-chloranilic acid [p-CA], and ion pair complexation reactions with some acidic dyes, namely, bromophenol blue [BPB], bromothymol blue [BTP] and bromocresol green [BCG]. In the first procedure the drugs were treated with DDQ or p-CA in acetonitrile, the colored products were quantified spectrophotometrically at 587 nm and 520 nm for mianserin and 457 nm and 520 nm for risperidone using DDQ and p-chloranilic acid, respectively. In the second procedure drugs were treated with acidic dyes in chloroform, the complexes formed are measured at 411 nm, 411 nm and 414 nm in case of mianserin and 415 nm, 415 nm and 419 nm for risperidone with BPB, BTB and BCG, respectively. The effect of several variables affecting color development was studied and the molar ratio of reactants was established in each case. Linearity ranges were found to be 12-55 mug ml-1, 40-200 mug ml-1, 2-10 mug ml-1, 2.5-12 mug ml-1 and 3-12 mug ml-1 for mianserin and 25-135 mug ml-1, 40-220 mug ml-1, 3.5-15 mug ml-1, 4-18 mug ml-1 and 4-18 mug ml-1 for risperidone using DDQ, p-chloranilic acid, BPB, BTB and BCG, respectively. The proposed methods were applied successfully for the analysis of both drugs in raw material and in pharmaceutical dosage forms with good accuracy and precision. The results were compared statistically with reference methods commonly used for the determination of the drugs