Extraction-Free Ion-Pair Methods for the Assay of Trifluoperazine Dihydrochloride in Bulk Drug, Tablets, and Spiked Human Urine Using Three Sulfonphthalein Dyes

Abstract

Three simple and sensitive extraction-free spectrophotometric methods are described for the determination of trifluoperazine dihydrochloride (TFH). The methods are based on ion pair complex formation between the nitrogenous compound trifluoperazine (TFP) converted from trifluoperazine dihydrochloride and sulfonphthalein dyes, namely, bromocresol green (BCG), bromothymol blue (BTB), and bromophenol blue (BPB) in dichloromethane medium in which all the above experimental variables were circumvented. The colored products are measured at 425 nm in the BCG method, 415 nm in the BTB method, and 420 nm in the BPB method. The stoichiometry of the ion-pair complexes formed between the drug and dye (1:1) was determined by Job’s continuous variations method, and the stability constants of the complexes were also calculated. These methods quantify TFP over the concentration ranges of 1.25–20.0 μg/ml in the BCG method, 1.5–21.0 μg/ml in the BTB method, and 1.5–18.0 μg/ml in the BPB method. The molar absorptivity (l·mol–1·cm–1) and Sandell sensitivity (ng/cm2) were calculated to be 2.06·104 and 0.0197; 1.82·104 and 0.0224; and 2.22·104 and 0.0183 for the BCG, BTB, and BPB methods, respectively. The methods were successfully applied to the determination of TFP in pure drug, pharmaceuticals, and in spiked human urine with good accuracy and precision.