Molecularly imprinted β-cyclodextrin polymer as potential optical receptor for the detection of organic compound

A molecularly imprinted β-cyclodextrin polymer (MIβ-CDP) was synthesised using β-cyclodextrin (β-CD) as monomer that is cross-linked using toluene 2,4-diisocyanate (TDI); N-phenyl-1-naphthylamine (NPN) was used as the template molecule. The MIβ-CDP was fluorometrically characterised using a fibre optic cable attached to a self-designed flow-cell. The fluorescence emission spectrum of the MIβ-CDP was found to be associated with the activity of binding to NPN through batch rebinding analysis. Heterogeneous binding models (bi-Langmuir and Freundlich isotherms) that yield information on binding sites affinity distribution and heterogeneity index were employed to characterise this process. Analytical studies demonstrated that the fluorescence intensity was linear in the analyte concentration range up to 1.6 × 10−4 M with a limit of detection (LOD) of 1.38 μM. The non-linear response range was successfully modelled using a power relation that is similar to the Freundlich isotherm and the dynamic response was successfully extended to 2.0 × 10−3 M. The response time of the system was determined to be 90 s with an optimum flow of 0.02 mL s−1 and methanol as analyte solvent. Molecular imprinting efficiently promoted a better sensing signal by increasing the binding-affinity and substrate-selectivity towards the template molecule, compared with the control polymer prepared in its absence. The sensitivity was enhanced by about 16% as measured with three different concentrations of analyte. The sensing receptor was successfully regenerated using acetonitrile and can be reused with no significant decay in intensity with a relative standard deviation (RSD) value of 2.24% (n = 13). The sensor developed was successfully tested for analytical determination of NPN.