A Simple Counting-Based Measurement for Paper Analytical Devices and Their Application

Abstract

This work introduces the concept of a counting-based measurement on paper analytical devices (cPADs) to improve the utilization of numerous reactions. The design of cPADs consists of two layers of paper substrates; the first layer contains a central sample zone combined with a radial surrounded by 12 detection zones that are predeposited with the various reagents, and the second layer acts as a connection channel between the sample zone and each detection zone. The solution can vertically flow from the first to the second layer and then move through the area to each subsequent detection zone. The analyte level can be evaluated by counting the number of detection zones that change color from a blank signal. Furthermore, our cPADs exhibit a capability of implementation for a broad series of reactions. Compared to the dPAD technique, some reactions that are possibly difficult to apply in such devices can be wholly enabled in our devices. The final color reaction on cPADs can apparently occur due to its identity. We applied this technique to the monitoring of carbaryl (CBR) and copper ions (Cu2+) using different reactions, including azo-coupling and complexation, respectively. Accordingly, this indicates an excellent result validated using the more traditional methods. Our cPADs can be applied for rapid screening of both CBR and Cu2+ in water samples with outstanding accuracy and precision using a naked-eye measurement by a relatively unskilled person. We offer a simple platform on PADs for rapid screening, combining high cost-effectiveness within a miniaturized platform designed for use with onsite applications, which is thus suitable for several different reactions.

Recent Developments in Paper-Based Sensors with Instrument-Free Signal Readout Technologies (2020–2023)

“…In this study, the number of colored bars can be employed to identify the amount of H 2 O 2 . A similar study was also reported by Khachornsakkul et al [27], who employed a novel counting-based instrument-free signal readout device designed to detect the Cu 2+ and carbaryl (CBR) in real samples. The paper analytical device, depicted in Figure 3, is constructed with two layers of filter paper; the initial layer is equipped with twelve detection zones, all of which have been pre-loaded with specific reagents to measure Cu 2+ and CBR, and the subsequent layer is used to establish a pathway between the sample and detection zones.…”

Gold Nanomaterial-Based Microfluidic Paper Analytical Device for Simultaneous Quantification of Gram-Negative Bacteria and Nitrite Ions in Water Samples

“…Conversely, as the sample volume exceeded 30.0 μL, the analytical signals for both detections gradually decreased. This decline can be attributed to the larger sample volume potentially leading to solution leakage from the paper substrate . We thus selected the sample volume of 25.0 μL as an optimal level for achieving the simultaneous detection of E.…”

“…This decline can be attributed to the larger sample volume potentially leading to solution leakage from the paper substrate. 42 We thus selected the sample volume of 25.0 μL as an optimal level for achieving the simultaneous detection of E. coli and NO 2 − . Likewise, we introduced a sample volume of 5.0 μL into the sample inlet for five times to assess the impact of the number of sample drops on our assay.…”

A novel pyrenyl-furan hydrazone on paper-based device for the selective detection of trinitrotoluene

“…Initially, 2 mL of the sensory solutions of T1 or T2 in THF (0.25 mM) were dropped directly onto filter sheets. [39][40][41] Subsequently, images of the T1 or T2 paper-based device were dropped before being exposed to (10 and 100 mM) TNT solutions for 5 minutes. Additional photographs were obtained using a portable UV lamp with an excitation wavelength of 365 nm.…”