Utilizing the μPAD as an instrument-free technique for thequantitative analysis of Ni+۲ ions

Recently, there has been a significant interest in Microfluidic Paper-based analytical devices (µPADs), which are cost-effective chemical detectors that are designed for use at the sampling point. These devices have several advantages, including being small and user-friendly, having a simple and rapid fabrication process, working with small amounts of samples, being reproducible, and being environmentally compatible, thus making them one of the most extensively researched topics today. One limitation of most µPADs, however, is the need for peripheral equipment, such as a camera and photo analyser software, to analyse the colour intensity for quantitative assays. In this study, we present a straightforward and instrument-free technique for quantifying a sample's analyte by measuring the distance of colour development. This so-called distance-based detection method enables µPADs to operate in a more portable and independent manner than traditional µPADs that require peripheral equipment. Specifically, this article demonstrates the effectiveness of this approach by measuring nickel with metal complexation detection chemistries. The results indicate that an increase in the concentration of nickel in the sample leads to an increase in the final colour length. This method has the potential to be highly applicable in a wide range of applications.