Lowering the limit of detection of ion-selective membranes backside contacted with a film of poly(3-octylthiophene)
Date
2019Discipline/s
FarmaciaAbstract
Nanometer-sized membranes (thickness of ca 200 nm) backside contacted with a film of poly(3-octylthiophene)
(POT) are here interrogated by an electrochemical protocol based on the accumulation and stripping of the
target ion aiming at lowering its limit of detection (i.e., in the sub-micromolar range). Thus, using a membrane
based on silver ionophore IV (Sigma-Aldrich), which is one of the ionophores regularly used in ion-selective
membranes presenting a large binding constant (log βAg–ionophore≈12), it is possible to detect 5 nM concentration
of silver with the established methodology. Importantly, this is a 1000-fold lower concentration of
silver compared with the case in which the same membrane is subjected to traditional cyclic voltammetry.
Essentially, the control of the oxidation state of the POT film by applying a constant potential during a certain
period of time (i.e., Eapp=0 V for 720 s) in the presence of silver ions in the sample solution (from 5 to 100 nM)
allows ...