Label free electrochemical sensors for Pb(II) detection based on hemicellulose extracted from Opuntia Ficus Indica cactus.

We aim to develop an electrochemical sensor for a divalent metal ion (lead II), a highly toxic water contaminant. We explore a sensor formed with a hemicellulose polysaccharide extracted from the Opuntia Ficus Indica cactus associated with agarose as a sensitive layer deposited on a gold electrode. This sensor combines the functional groups of hemicellulose that could form a complex with metal ions and agarose with gelling properties to form a stable membrane. The sensor demonstrated a loading ability of Pb, with higher affinity compared to other metal ions such as Hg, Ni and Cu, thanks to the chemical structure of hemicellulose. The detection was measured by square wave voltammetry based on a well-defined redox peak of the metal ions. The sensor shows high sensitivity towards Pb with a detection limit of 1.3 fM. The application in river and sea water using the standard addition method for lead detection was studied.