Chemiluminescence determination of timolol maleate by gold nanoparticles-catalyzed luminol–N-bromosuccinimide system

A new chemiluminescence (CL) method combined with flow injection technique was developed for the determination of timolol maleate. Gold nanoparticles was found to catalyze the CL reaction of luminol with N-bromosuccinimide in an alkaline condition. The CL signal was furtherly enhanced significantly when timolol maleate was presented in the reaction system. But timolol maleate alone inhibited the CL signal from luminol–N-bromosuccinimide reaction slightly. Under the selected conditions, the enhanced CL intensity was linearly related to timolol maleate concentration in the range of 0.01–5.0 mg/L with a detection limit of 7.6 μg/L. The relative standard deviation was 2.7% for 11 repeated measurements of 0.1 mg/L timolol maleate solution. The proposed method was applied to the determination of timolol maleate in eye drops and in spiked human urine. A discussion on the possible CL reaction mechanism was also presented.