All solid state chronopotentiometric ion-selective electrodes based on ferrocene functionalized PVC

Abstract

a b s t r a c tAn all solid contact ion-selective electrode based on poly(vinyl chloride) covalently modified with ferrocene moieties allows one to operate the membrane in a chronopotentiometric sensing mode. The membrane is considered as initially non-perm-selective towards anions, and an applied anodic current provokes a defined anion flux in direction of the membrane. With this protocol, a variety of anions can be depleted at the membrane surface. Since this model system does not yet contain an ionophore, their order of preference follows the expected Hofmeister selectivity sequence. The all solid-state configuration tolerates an imposed current density of 1.4 lA mm À2 , which translates into an upper detection limit of ca. 1.2 mM. Higher current densities of up to 31.2 lA mm À2 are possible with addition of freely dissolved alkyl ferrocene derivative for an expected upper detection limit of 17.0 mM. Numerical simulations are performed in order to establish the fundamental basis of the mechanism that takes place in this all solid-state membrane electrode. The oxidation of bound Fc and the ion-transfer process are considered in the simulation. In view of developing an analytical sensor, different anions are tested. A linear range of two orders of magnitude from 0.01 to 1 mM is found. The membranes are evaluated over several days, displaying practically the same slopes and intercepts, with a RSD of less than 2%. Electrochemical limitations of free Fc and bound Fc are critical evaluated. This approach should allow one to develop a new family of solid-state chronopotentiometric ion sensors that require relatively high current densities.

Ion Transfer Voltammetry at Thin Films Based on Functionalized Cationic [6]Helicenes

“…They are important analytical tools in fundamental chemical science and in applied work such as clinical, industrial and forensic diagnostics and environmental monitoring . In recent years, there has been significant interest of scientific attention for sensors especially in the field of the solid‐contact ion‐selective electrodes (SC‐ISEs) . The SC‐ISEs represent a promising alternative to conventional liquid contact ISEs as potential candidates to replace the inner filling solution and the reference Ag/AgCl element.…”

“…used freely dissolved dimethylferrocene for amperometric detection of heparin and Pawlak et al . has introduced ferrocene covalently attached to the PVC backbone for chronopotentiometric carbonate detection . Unfortunately, the major drawback of ferrocene‐based membranes is the irreversible behavior of oxidized ferrocenium in the presence of chloride ions in thin films due to the formation of the complex Fc + ‐Cl − .…”

Covalent Functionalizations of Poly(vinyl chloride) in Tune with Applications: An Update

“…Poly(vinyl chloride), particularly in its modified forms, has been one of the largest used polymers in the design of such membranes. Bakker's school undertook diverse functionalizations of high molecular weight PVC for elaborating ion-selective membrane electrodes, providing the use of click chemistry [32][33][34][35][36][37]. The ferrocene moiety was anchored onto PVC matrix via CuAAC of PVC-N 3 with ethynylferrocene.…”

“…Some advantages in the electrochemical process by using the thus-modified PVC, PVC-Fc (Fc = ferrocene; Figure 2A), were claimed. Indeed, in the chronopotentiometric measurements, the PVC-Fc-based membrane displayed a dual role: an ion-to-electron transducer and an initiator of the ion-transfer process from the aqueous to the membrane phase [35]; a selectivity was observed for the following Hofmeister series: chloride, nitrate, thiocyanate and perchlorate. Also, phenomena such as the diffusion and the electrochemical behavior of PVC-Fc, a high molecular weight polymer with a single redox active unit, were noticed [36].…”

“…It was revealed that DMF favored the substitution mechanism and DMSO favored the elimination one. However, addition of THF to DMSO in 1:2 ratio (35) enhanced the substitution at ambient temperature. In DMF solution, higher temperatures were positive for increasing substitution yields.…”