Phosphorus and Arsenic Sensors for Real Time Environmental Monitoring

The objective of this proposal is to develop an electrochemical sensing electrode for the real-time analysis of phosphate, arsenate, and arsenite. This electrode will be based on the interaction of these ions with nanoporous oxide thin-films, and the detection of these interactions with impedance spectroscopy. Given a suite of oxide films and the infinite amount of frequencies available to spectroscopic techniques we are confident we will be able to select frequencies for detection of each anion with minimal interference from other ions in the samples. The project will be completed by examining the behavior of individual anions reacting with electrodes prepared with iron oxide, manganese oxide, and titanium dioxide. Four different concentrations of the anions at three pH values will be tested. The impedance spectrum of each of these conditions will be recorded for each anion on each of three oxide electrodes. Next, we will prepare electrodes with a combination of the three oxides, and based on the impedance spectroscopy results with the individual anions and individual oxide electrodes, we will select frequencies that are unique for the detection of each anion, and test combinations of arsenate and phosphate to examine interference patterns and fine frequencies and conditions that allow the independent measurement of each anion. We will later include arsenite in these studies, but first being careful to note the kinetics of the oxidation of arsenite to arsenate during the time-frame of the analytical processing of the impedance signal, which is indeed quite rapid. Ultimately, we will evaluate the sensor by comparing sensor output with measured concentrations of the ions in actual field samples. We will collect samples from wastewater treatment outlets (point source of phosphate), agricultural settings (non-point source of phosphate), and also anticipate having the DNR furnish us real-world groundwater samples that are contaminated with arsenic.