Chelating electrodes as taste sensor for the trace assessment of metal ions

Impedance spectroscopy combined with principal component analysis allows the trace detection of metal ions. The detection system is based on two modified electrodes, each of them containing a chelating agent (pyrocatechol violet and a nitrilotriacetic derivative); as the chelator is able to capture the metal ion at very low concentrations, important electrical changes are produced on the surface environment, generating patterns with different features for each ion. The system is able to differentiate eight metal ions (Al3+, Fe3+, Cd2+, Pb2+, Hg2+, Cu2+, Ca2+ and Ag+) at micromolar levels in ultrapure water. The method allows the detection of metal ions in aqueous samples without the need of sample conditioning, rinsing steps or the addition of probes. Selecting the appropriate frequencies and sensors, the array can also be applied to different aqueous systems such as bottled mineral water or concentrated NaCl (27%) yielding similar results.