Gold nanoparticle-enhanced chemiluminescence detection for CE

Introducing gold nanoparticles (AuNPs) to the running buffer further improved the sensitivity of luminol-H2O2 chemiluminescence (CL) detection for CE. This has led to the development of sensitive CE-CL assays of biomedically interesting compounds. Epinephrine and norfloxacin were taken as the model analytes. Epinephrine inhibited light emission from the AuNP-catalyzed CL while norfloxacin enhanced it. The CE-CL assays had detection limits of 6.9 x 10(-9) M for epinephrine and 7.3 x 10(-9) M for norfloxacin. It was noted that in the absence of AuNPs no CE-CL analytical signal was produced by epinephrine at 4.0 x 10(-5) M or norfloxacin at 1.5 x 10(-3) M under similar experimental conditions. Fluorescence spectroscopic measurements showed that although the fluorescence excitation/emission maxima remained the same, the fluorescence lifetime of luminol increased significantly in the presence of AuNPs (tau(2) increased from 8.49 +/- 0.12 to 9.18 +/- 0.047 ns in a two-exponential fit), indicating that the excited states of luminol molecules were stabilized through the interaction between luminol molecules and AuNPs. Finally, quantitation of epinephrine and norfloxacin in biological samples such as human urine by using the present AuNP-enhanced CE-CL method was demonstrated.