An Electronic Tongue Designed to Detect Ammonium Nitrate in Aqueous Solutions

An electronic tongue has been developed to monitor the presence of ammonium nitrate in water. It is based on pulse voltammetry and consists of an array of eight working electrodes (Au; Pt; Rh; Ir; Cu; Co; Ag and Ni) encapsulated in a stainless steel cylinder. In a first step the electrochemical response of the different electrodes was studied in the presence of ammonium nitrate in water in order to further design the wave form used in the voltammetric tongue. The response of the electronic tongue was then tested in the presence of a set of 15 common inorganic salts; i.e.; NH4NO3; MgSO4; NH4Cl; NaCl; Na2CO3; (NH4)(2)SO4; MgCl2; Na3PO4; K2SO4; K2CO3; CaCl2; NaH2PO4; KCl; NaNO3; K2HPO4. A PCA plot showed a fairly good discrimination between ammonium nitrate and the remaining salts studied. In addition Fuzzy Art map analyses determined that the best classification was obtained using the Pt; Co; Cu and Ni electrodes. Moreover; PLS regression allowed the creation of a model to correlate the voltammetric response of the electrodes with concentrations of ammonium nitrate in the presence of potential interferents such as ammonium chloride and sodium nitrate.