Optimisation of the conditions for stripping voltammetric analysis at liquid–liquid interfaces supported at micropore arrays: a computational simulation

Abstract

Micropore membranes have been used to form arrays of microinterfaces between immiscible electrolyte solutions (µITIES) as a basis for the sensing of non-redox-active ions. Implementation of stripping voltammetry as a sensing method at these arrays of µITIES was applied recently to detect drugs and biomolecules at low concentrations. The present study uses computational simulation to investigate the optimum conditions for stripping voltammetric sensing at the µITIES array. In this scenario, the diffusion of ions in both the aqueous and the organic phases contributes to the sensing response. The influence of the preconcentration time, the micropore aspect ratio, the location of the microinterface within the pore, the ratio of the diffusion coefficients of the analyte ion in the organic and aqueous phases, and the pore wall angle were investigated. The simulations reveal that the accessibility of the microinterfaces during the preconcentration period should not be hampered by a recessed interface and that diffusional transport in the phase where the analyte ions are preconcentrated should be minimized. This will ensure that the ions are accumulated within the micropores close to the interface and thus be readily available for back transfer during the stripping process. On the basis of the results, an optimal combination of the examined parameters is proposed, which together improve the stripping voltammetric signal and provide an improvement in the detection limit.

Ion‐Transfer Electrochemistry of Rat Amylin at the Water–Organogel Microinterface Array and Its Selective Detection in a Protein Mixture

“…The steady-state behavior is also shown in the background-subtracted CV (Figure 1 B, inset). A similar phenomenon has been observed in the case of simple ion transfer at the mITIES, [19] for which, owing to the low diffusion coefficient in the viscous organic phase and the confined geometry defined by the micropore walls, the analyte accumulated in the organic phase close to the interface. The lack of a "diffusional tail" on this reverse peak suggests that diffusion of rA in the organogel phase is not the controlling step.…”

“…As a result, it is hypothesized that rA transfers to the organic phase, where it accumulates, owing to its relatively large size (molecular mass 3.9 kDa) and low diffusion coefficient in the gelled organic phase, rather than diffusing away from the interface. A similar phenomenon has been observed in the case of simple ion transfer at the mITIES, [19] for which, owing to the low diffusion coefficient in the viscous organic phase and the confined geometry defined by the micropore walls, the analyte accumulated in the organic phase close to the interface. This accumulation effect may result in a thin layer of polypeptide in the organic gel, which is subsequently stripped back on the reverse sweep; however, the presence of an adsorbed layer cannot be fully excluded at present.…”

Microscopic gel–liquid interfaces supported by hollow microneedle array for voltammetric drug detection

“…The gel phase forms a recessed interface at the aqueous side of the ITIES (as it can be seen in figure1B). Computational simulations have shown that this configuration is optimal for stripping voltammetry, as transport of analyte species to the gel microinterface improves with a hemispherical diffusion regime during the preconcentration step [38] . Once they are transferred to the organic phase, they remain in the vicinity of the interface because of the reduced mass transport caused by both the linear diffusion and the lower diffusion coefficient in the PVC gel.…”

Dynamic electrochemistry with ionophore based ion-selective membranes

“…10,[15][16][17][18][19][20][21][22] Both ohmic drop and capacitive currents are dramatically diminished utilizing these ultra-small liquidliquid interfaces. For instance, nanopipets, micro and nanofabrication are used to develop massive sensor arrays.…”