Enhancement of the chemiluminescence of permanganate-formaldehyde system by gold/silver nanoalloys and its application to trace determination of melamine

Gold/silver alloy nanoparticles (Au/Ag NPs) are shown to exert a beneficial effect on the chemiluminescence (CL) reaction of permanganate-formaldehyde in the presence of sodium dodecyl sulfate micelles. The Au/Ag NPs can be prepared by chemical reduction and display better catalytic properties than their monometallic counterparts. Transmission electron microscopy, energy dispersion X-ray spectrometry and UV-vis spectroscopy were used to characterize the Au/Ag NPs. Melamine at even ultratrace level inhibits the action of nanoparticles and therefore decreases the intensity of CL. This finding forms the basis for a method for the determination of melamine in the 0.01-35 ng mL(-1) concentration range, with a detection limit of 8 pg mL(-1). The method was successfully applied to the determination of minute concentrations of melamine in powdered milk samples.