Colorimetric determination of fexofenadine by citrate-capped silver nanoparticles after extraction by molecularly imprinted polymer

In this work, we describe a selective and sensitive colorimetric method for the extraction and determination of fexofenadine (FEXO) in biological samples. The proposed method combines the benefits of a molecularly imprinted polymer (MIP) for selective sample clean-up and preconcentration with a sensitive colorimetric assay based on citrate -capped silver nanoparticles (AgNPs) probes. The MIP was successfully synthesized by a chemical method using pyrrole (PY) as monomer and FEXO as a template. The template molecules were removed by ethanol /water solution (3:1, v/v) and this solution was selected as the extraction solvent .In this two-step the analyte (FEXO) was isolated from the matrix by MIP .The extraction solvent containing the FEXO molecule is then transferred to aqueous dispersion of citrate-capped AgNPs.The interaction between amino groups of FEXO and citrate-capped AgNPs induces rapid aggregation of AgNPs accompanied by a naked-eye visible color change,resulting in precise quantification of FEXO that can be detected by a UV-visible spectrophotometer. This aggregation decrease original absorbance of Ag NPs at 392 nm and appear a new absorption band above 522 nm. Several significant parameters controlling the performance of the MIP and colorimetric method were examined and optimized using multivariate optimization method. Plackett–Burman design (PBD) and central composite design (CCD) were used for optimization step. Under the selected optimal conditions the absorbance intensity ratio (A 522nm /A 392nm ) is correlated with the FEXO concentrations over the range of 0.05-5 μM and the detection limit is 25nM.