Evaluation of Tropaeolin 000-1 as a Colorimetric Reagent for Assay of Duloxetine and Escitalopram in Solid Dosage Form

Purpose: To explore the application of tropaeolin 000-1 reagent for the rapid, precise and accurate determination of duloxetine hydrochloride (DX) and escitalopram maleate (ECT).
Methods: Determination of DX and ECT was based on the formation of complexes between the dye, DX and ECT in 0.1 M HCl. The resulting chromogen showed a maximum wavelength of absorption at 502 and 503 nm for DX and ECT, respectively. This method was validated for analytical parameters such as linearity, precision, accuracy, robustness, and ruggedness according to the guidelines of International Conference on Harmonization (ICH) and United States Pharmacopoeia (USP).
Results: The absorbance of the each chromogen formed with DX and ECT was linear over the range of 4 - 30 and 2.5 - 27.5 μg mL^-1 for DX and ECT, with 0.9968 and 0.9979 as the regression coefficient, respectively. The limits of detection (LOD) were 0.0045 and 0.0015 μg mL^-1 for DX and ECT, respectively, with the limits of quantification (LOQ) at 0.5 and 0.08 μg mL^-1. The recovery (accuracy) of the methods resulted in low RSD values of 0.856 – 0.983 % for DX and 0.765 – 0.987 % for ECT.
Conclusion: The developed method shows a high degree of accuracy and precision for the determination of DX and ECT. Thus, tropaeolin 000-1 reagent is versatile for determining the contents of DX and ECT in their formulations.

Keywords
Duloxetine; Escitalopram; Tropaeolin 000-1; Extractive spectrophotometry; Validation