Study on the Supramolecular Interaction of Cucurbit [7]uril with Ephedrine Hydrochloric Acid by Fluorescent Probe and its Analytical Application

Abstract

The inclusion interaction of cucurbit[7]uril (CB[7]) with ephedrine hydrochloric acid (EP) was studied using fluorescent probe method. Significant quenching of the fluorescence intensity of the CB[7]-palmatine (PAL) fluorescent probe was observed when EP was added, showing that EP was accommodated into the hydrophobic cavities of CB[7] and an endo-inclusion complex was formed. The hydrophobic interaction between CB[7] and EP mainly contributed to the formation of 1:1 type CB[7]-EP. Its complex constant was determined as K = (2.82 ± 0.52) ×1011 M⁻¹. Based on the significant quenching of the supramolecular complex fluorescence intensity, a new spectrofluorimetric method with high sensitivity and selectivity was developed for the determination of EP in aqueous solution. The fluorescence quenching values (ΔF) showed good linear relationship with EP concentrations from 0.011 μg mL⁻¹ to 2.8 μg mL⁻¹ with a detection limit 0.0036 μg mL⁻¹. The proposed method had been successfully applied to the determination of EP in its pharmaceutical dosage forms and in urine samples with good precision and accuracy. In addition, molecular modeling calculations results indicated the partial inclusion of EP in the hydrophobic cavity of CB[7]. The interaction mechanism between the CB[7] and EP was confirmed by 1H-NMR spectrum.