In-situ detection of atrazine and its metabolites contamination in natural waters
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Water and soil contamination caused by extensive atrazine (ATZ) application in agriculture, could be a potential risk to the environment and human health. Common analytical methods are expensive and complex. A sensor for low-cost and simple detection of ATZ and its metabolites, deethylatrazine (DEA) and deisopropylatrazine (DIA), in aqueous solutions was developed by combining colloidal crystal with molecular imprinting technique. The sensor is formed by 3D interconnected macroporous structure with numerous nanocavities derived from ATZ and its metabolites imprinting in a thin polymeric film. The MIPs were fabricated with acrylic acid monomers crosslinked by ethylene glycol dimethacrylate with 4:1 molar ratio, polymerized under UV radiation initiated by azobisisobutyronitrile. The films were characterized by Fourier Transform Infrared spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The MIPs were incubated in solutions of each target at variable concentrations. Target molecules were specifically absorbed in nanocavities and caused swelling in the polymer film resulting in changes of Bragg diffraction peak wavelength. Kinetic tests showed that rebinding equilibrium was reached within 20 minutes. The sensor had a dynamic range of 0.1 to 10 ppb for quantifying target analytes in aqueous solutions with limit of detection of 0.1, 0.2, and 0.3 ppb, and limit of quantification of 0.33, 0.66, and 1 ppb for ATZ, DEA, and DIA, respectively. Cross-reactivity tests were conducted in 1 and 5 ppb solutions combining all three targets and showed absence of positive interferences effects and low probability of false positives given by individual sensors. Ionic strength effect on MIPs investigation showed up to 26 percent decrease and 23 percent increase in MIP response for NaCl and CaCl2, respectively. Presence of NOM caused 28 percent and 35 percent increase in wavelength shift for NIPs and MIPs, respectively. Rinsing NIPs before measuring the reflectance spectra resulted in less increase in wavelength shift. Natural waters samples were collected after rain events and were characterized for physicochemical properties and the content of ATZ, DEA, and DIA to be eventually used for MIPs application in them. MIPs were examined in natural waters spiked with target molecules, showing good agreement with real concentrations of targets. The resulting molecularly imprinted polymer (MIP) yields rapid and efficient detection of target molecules in aqueous solutions close to environmentally relevant concentrations.
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Ph. D.