Spectrophotometric and visual detection of the herbicide atrazine by exploiting hydrogen bond-induced aggregation of melamine-modified gold nanoparticles

We report on a method for the determination of the herbicide atrazine in tap water samples using melamine-modified gold nanoparticles (Mel-AuNPs). If a solution containing atrazine is added to a solution of such NPs, a color change occurs from wine-red to blue. This is due to a transition from monodisperse to aggregated Mel-AuNPs and caused by strong hydrogen bonding between atrazine and melamine. The color change can be monitored by a UV-vis spectrophotometer or with bare eyes. The ratio of the absorbances at 640 and 523 nm is linearly related to the logarithm of the atrazine concentration in the 0.165 to 16.5 mu M range, and (with different slope) in the 16.5 mu M to 330 mu M range. The detection limit of atrazine is as low as 16.5 nM (S/N = 3). The method was successfully applied to the determination of atrazine in spiked tap water and gave recoveries that ranged from 72.5 % to 102.3 %.