A Sustainable Spectrofluorimetric Quenching Approach for Determination of Pentoxifylline or Donepezil HCl via Complexation With Erythrosine B: Application to Tablets and Human Plasma

This work introduces a novel, green switch on-off spectrofluorimetric quenching method using erythrosine B (EB) for nano-trace determination of pentoxifylline (PTX) or donepezil HCl (DPZ) in tablets and spiked plasma, enabling rapid clinical monitoring. The suggested approach relies on the quenching effect of either DPZ or PTX on the intrinsic fluorescence of EB, various experimental conditions influencing fluorescence quenching were investigated and optimized. An ion pair complex is formed between the cationic amino group in either drugs and the anionic phenolic group of EB at mild acidic conditions using Britton-Robinson buffer. After excitation at 528 nm, the fluorescence quenching intensities were measured linearly at 552 nm across the range (50-1000 ng/mL) for PTX with quantification limits of 16.76 ng/mL and over the range (20-500 ng/mL) for DPZ with limit of quantification 17.56 ng/mL for DPZ. The suggested method exhibited high % recoveries, confirming its reliable applicability in complicated matrices. The validation of the suggested methodology was further performed in accordance with the International Conference of Harmonization (ICH Q2R2) recommendations. Furthermore, the method's greenness, blueness and whiteness profiles was investigated, revealing its remarkable sustainability.