Functionalized nanoporous track-etched β-PVDF membrane electrodes for lead(ii) determination by square wave anodic stripping voltammetry

Abstract

Track-etched functionalized nanoporous -PVDF membrane electrodes, or functionalized membrane electrodes (FME), are thin-layer cells made from track-etched, poly(acrylic acid) (PAA) functionalized nanoporous -poly(vinylidene fluoride) (-PVDF) membranes with thin Au films sputtered on each side as electrodes. The Au film is thin enough that the pores of the membranes are not completely covered. The PAA functionalization is specifically localised in the walls of the nanoporous -PVDF membrane by radio grafting. The PAA is a cation exchange polymer that adsorbes metal ions, such as Pb 2+ , from aqueous solutions thus concentrating the ions into the membrane. After a calibrated time the FME is transferred to an electrochemical cell for analysis. A negative potential is applied to the Au film of the FME for a set time to reduce the adsorbed ions onto the Au film working electrode. The other metalized side of the FME functions as a counter electrode. Finally, square-wave anodic stripping voltammetry (SW-ASV) is performed on the FME to determine the metal ion concentrations in the original solution based on calibration. The calibration curve of charge versus log concentration has a Temkin isotherm form. The FME membranes are 9 m thick and have 40 nm diameter pores with a density of 10 10 pores/cm 2. This high pore density provides a large capacity for ion adsorption. Au ingress in the pores during sputtering forms a random array of nanoelectrodes. Like surface modified electrodes for adsorptive stripping voltammetry, the pre-concentration step for the FME is performed at open circuit. The zero current intercept of the calibration for Pb 2+ is 0.13 ppb (g/L) and a detection limit of 0.050 ppb based on 3S/N from blank measurements. Voltammetry (CV) and chronoapmerometry (CA) were used to characterize the system. The apparent diffusion coefficient (D) for Pb 2+ in the PAA functionalized pores was determined to be 2.44 x 10-7 cm 2 /s and the partition coefficient (pK M) was determined to be 3.08. The maximum allowable levels for toxic metals in water are now set at low ppb (g/L) levels. The maximum levels of Pb 2+ in potable water established the European Environmental Agency (EEA) the United States Environmental Protection Agency (EPA) and recommendations from the World health Organisation (WHO) are 7.2, 15.0, and 10.0 ppb respectively and the goal of the United States EPA is zero. 1-3 Reliable quantification of these low concentrations is difficult time consuming and expensive. Also, the analysis equipment is not portable so the samples have to be sent a centralised lab which typically involves a 24 hour turn around time, which means that pollution events can be missed, or detected too late. Electrochemical analysis techniques, such as anodic stripping voltammetry (ASV), are generally inexpensive, rapid and portable. The electrode of choice for measuring trace levels of toxic metal ions by ASV has been the dropping mercury electrodes (DME). 4 DMEs and mercury film electrodes are very sensitive, due to their high capa...

Track‐Etched Nanopore/Membrane: From Fundamental to Applications

“…Several polymers have been used to design track‐etched membrane including polyethylene terephthalate (PET), [ 37 ] polycarbonate (PC), [ 60 ] polyimide (PI), [ 65 ] polyvinylidene fluoride (PVDF), [ 66 ] and polypropylene (PP). [ 67 ] The PET is one of the most studied materials for track etching technology.…”

Poly(4-vinyl pyridine) radiografted PVDF track etched membranes as sensors for monitoring trace mercury in water

“…After gold sputtering, the functionalized track-etched membranes will be used as electrodes for SW-ASV analysis (Wade and Clochard, 2008;Wade et al, 2011;Bessbousse et al, 2011). SW-ASV measurements were performed using Hg standards and 1 mM NaCl/HNO 3 electrolyte.…”

“…PVDF-g-P4VP track-etched membranes were changed into an electrochemical nanoporous sensors, called CAPTÔT, thanks to the fabrication protocol described in (Wade and Clochard, 2008;Wade et al, 2011;Bessbousse et al, 2011). CAPTÔT was then immersed in the aqueous solution to analyse for an adsorption time ranging from 30 min to 24 h. During this step, the mercury solvated ions present in the aqueous solution (if any) were trapped inside the sensor nanopores by complexation with P4VP.…”

Differences in fundamental reaction mechanisms between high and low-LET in recent advancements and applications of ionizing radiation

“…Some recent developments lead to production of sensors of water quality. 42 Reactive vinyl monomers are suitable for ion track grafting. However, when dealing with acrylate monomers, the grafted polymer chains have been observed to grow anarchically due to the large number of transfer reactions.…”