A Fluorometric Method for Diclofenac Determination in Liquid Formulations: Experimental and Computational Assessments

AbstractDiclofenac (DCF) is an important non‐steroidal anti‐inflammatory drug frequently used to relieve rheumatic pain and acute injuries. Therefore, determination of DCF in real‐life samples using an efficient and cost‐effective indirect method is vital in pharmaceutical science. The proposed novel method is based on the formation of a solid Zn‐BMHM complex (chemosensor BMHM; (E)‐1‐((((1H‐benzo[d]imidazol‐2‐yl)methyl)imino)methyl)‐5‐methylphenol) via the displacement of zinc ions from the Zn‐DCF complex in an ethanol medium. The method consists of rapid precipitation steps that prevent interference effects and a turn‐on fluorescence effect by using a chemosensor. The increase in fluorescence intensity was linearly correlated with the concentration of Zn‐DCF solution over the range of 5.0–50.0 µM (R2: 0.999) with a LOD value of 1.64 µM. The method was applied to liquid pharmaceutical formulations and obtained excellent recovery values (99.09%–103.9%). Geometry optimization, molecular orbitals, and NBO population analyses were performed using density functional theory to display the exchange reaction's characteristics between ligand DCF and chemosensor BMHM. Global reactivity parameters and local interaction sites on the DCF and BMHM were examined in detail in view of the analyzed reaction. Theoretical assessments supported the analysis of reaction selectivity towards the BMHM ligand.