A simple spectrophotometric methods has been developed for the determination of nortriptyline hydrochloride in pure and in pharmaceutical formulations based on the formation of ion pair complexes with sudan II (SII), sudan IV (SIV) and sudan black B (SBB). The selectivity of the method was improved through extraction with chloroform. The optimum conditions for complete extracted colour development were assessed,. The absorbance measurements were made at 534, 596, and 649 nm for SII, SIV and SBB complexes, respectively. The calibration graph was linear in the range 0.5 – 28, 0.5 – 37.5, and 0.5 – 31 µg ml-1 of the drug using the same reagents, respectively. The precision of the procedure was checked by calculateing the RSD of ten replicate determinations on 15 µg ml-1 of nortriptyline HCl and was found to be 1.7, 1.3, and 1.55 % using SII, SIV, and SBB complexes, respectively. The molar absorptivity and Sandell sensitivity for each ion pair were calculated. The proposed methods were successfully applied to the determination of pure nortriptyline HCl and in pharmaceutical formulations, and the results demonstrated that the method is equally accurate, pricise, and reproducible as the official method.


Sci. Pharm., 69, 151–160 (2001).