Rapid Analysis in Continuous-Flow Electrochemical Paper-Based Analytical Devices

Abstract

A simple and low-cost continuous-flow (CF) electrochemical paper-based analytical device (ePAD) coupled with thermoplastic electrodes (TPEs) was developed. The fast, continuous flow combined with flow injection analysis was made possible by adding two inlet reservoirs to the same paper-based hollow channel flowing over detection electrodes, terminating in a fan-shaped pumping reservoir. The upstream inlet reservoir was filled with buffer and provided constant flow through the device. Sample injections were performed by adding 2 μL of the sample to the downstream sample inlet. Differences in flow resistance resulted in sample plugs displacing buffer as the solution flowed over the working electrodes. The electrodes were fabricated by mixing carbon black and polycaprolactone (50% w/w). CF-TPE-ePADs were characterized with chronoamperometry using ferrocenylmethyl trimethylammonium as the electrochemical probe. Optimized flow rates and injection volumes gave analysis times roughly an order of magnitude faster than those of previously reported flow injection analysis ePADs. To demonstrate applicability, the CF-TPE-ePADs were used to quantify caffeic acid in three different tea samples. The proposed method had a linear range from 10 to 500 μmol L −1 and limits of detection and quantification of 2.5 and 8.3 μmol L −1 , respectively. Our approach is promising for fabricating simple, inexpensive, yet high-performance, flow injection analysis devices using paper substrates and easy-to-make electrodes that do not require external mechanical pumping systems or complicated valves.

SECM Investigation of Carbon Composite Thermoplastic Electrodes

“…PCL TPEs were also recently incorporated into microfluidic devices. 8,11 However, the signals from PCL TPEs change over time (PMMA and COC TPEs have not shown bulk signal changes over several months). 9,10 PCL is also a well-known biodegradable polymer, but its degradation time is not well controlled and takes up to two years in physiological conditions.…”

An overview of materials, processing, and applications for wearable electronics

“…The wicking paper ability is an important feature because it promotes conductive ink adhesion and allows the solution to flow through microfluidic tools without additional pumping [73,74]. The wicking capacity of paper, on the other hand, aids in the infiltration of the supporting electrolyte solution into the electroanalytical tool.…”

Flow-based System: A Highly Efficient Tool Speeds Up Data Production and Improves Analytical Performance

“…For the last point, as we knew very well that paper-based devices are a new platform for analytical detection. A simple and low-cost continuous-flow electrochemical paper-based analytical device (PAD) was presented 55 in 2020 by Henry's group. They utilized polycaprolactone (PCL) as a TPE binder to create our continuous-flow electrochemical μPADs.…”