Ion-transfer between immiscible liquids in a paper-based setup

Polish title: Przeniesienie jonów między niemieszającymi się cieczami w układzie papierowym

Funding source: National Science Centre Poland (NCN)

Project number: 2021/41/B/ST4/01324

PI: Martin Jönsson-Niedziółka

Total funding: 1 060 546,00 PLN

Timeframe: 01/04/2022 -31/03/2025 

Short description

The main scientific goal of the proposed project is to develop and evaluate sensors based on transfer of ions across the interface between two immiscible electrolyte solutions (ITIES) in paper-based systems. Ion-transfer voltammetry possesses a clear potential as a system for detection of analytes that are not electrochemically active. As such it complements, and can be combined with, traditional electrochemical approaches to sensing. It’s been a promising tool for decades, but has rarely managed the step outside well-controlled lab-environments. A key reason is that the system is often quite hard to handle, and sometimes conceptually difficult to grasp.

The main goal of this project is to make a significant contribution to bringing ion-transfer out of the laboratory and into the field or bedside. By combining ion-transfer electroanalysis with paper-based sensing, we can overcome the problems with liquid-liquid interface stability. Using the cellulose structure of the paper to stabilise the liquid phases can help create a more user-friendly setup for ITIES measurements. However, the combination of ion-transfer and paper also brings out several unique advantages. An “electrochemical pen”, with a gelled organic phase in an external pen-like probe that can be used to sample the paper-based analytical solution, can be combined with paper-based chromatographic separation of proteins for quick and simple analysis of samples. It can also be used for analysis of smaller molecules that can be pre-concentrated in the paper using a repeated “drip and dry” procedure or accumulated in the gel by “dip and pick” and the determined by stripping voltammetry.

For all this to be feasible, the interface between the paper-based aqueous phase and the organic gelled phase needs to be properly characterised, which will be an important part of the project. Using a combination of electrochemical tools, such as impedance spectroscopy and AC voltammetry with fluorescence microscopy we will investigate how ions and, especially, proteins interact with the paper-gel ITIES as compared to a normal ITIES and one with a liquid aqueous phase and gelled organic phase. During the course of the project we will construct sensors for model analytes and proteins and compare to the performance of standard ITIES sensors to evaluate their sensitivity and limit of detection.

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