“…The use of Amperometric sensors, that measure the current produced by the target analyte at an electrode with a constant voltage, has also been investigated widely (Beer et al, 1996(Beer et al, , 1997 showing some selectivity for dihydrogen phosphate and orthophosphate. Some involved measuring the reduction of the ammonium phosphomolybdate complex formed in the standard phosphomolybdate reaction (Quintana et al, 2004;Udnan et al, 2005) or anodic oxidation of molybdenum (Jonca et al, 2011), while others involved the use of electrodes embedded with ammonium molybdate (Berchmans et al, 2011). Others involved the use of phosphate sensitive enzyme electrodes, designed for potential environmental applications, and are able to detect orthophosphates down to 3 µg/L (Midgley, 1986;Engblom, 1998;Villalba et al, 2009;Rahman et al, 2006).…”