Spectrofluorimetric analysis of captopril based on its obstruction effect of the nanomaterial surface energy transfer between acridine orange and gold nanoparticles

A simple and sensitive method for detection of captopril was established based on its obstructive effect on nanomaterial sur- face energy transfer （NSET）. It was found that the acridine orange （AO） could be adsorbed onto the surface of citrated-gold nanoparticles （AuNPs） through electrostatic interaction. Incidentally, the fluorescence of AO was quenched owing to the dipole-dipole interaction of NSET between AO fluorophore and the AuNPs. However, captopril could obstruct the occurrence of NSET between AO and AuNPs effectively with the formation of Au-S covalent bonds between it and the AuNPs. Consequently, AO molecules were moved away from the surface of AuNPs leading to a decline of the energy transfer efficiency. Moreover, the fluorescence of AO could be gradually restored with the addition of captopril. Under the optimal conditions, the recovered fluorescence intensity correlated linearly with the concentration of captopril in the range of 400 nmol/L-2.0μmol/L with a detection limit of 71 μmol/L. Besides, the proposed method was successfully applied for the detection of captopril in troches with the recovery of 93%-102% and the RSD lower than 2.24%. The results were in good agreement with those obtained from the HPLC method,