Micro-array based on parafilm towards the opto-analysis of Cu( ii ), Cr( vi ), and Ni( ii ) ions in fish samples by specific indicators: a state-of-the-art approach

In this study, a parafilm-based colorimetric micro-array (PCMA) is introduced as a novel, low-cost sensor for the specific detection of copper (Cu(ii)), chromium (Cr(vi)), and nickel (Ni(ii)) ions in real samples. We developed a convenient and straightforward micro-array based on parafilm for creating hydrophobic and semi-hydrophobic areas for the colorimetric detection of three metal ions, namely, Cu(ii), Cr(vi), and Ni(ii) ions, using color picker software installed on a smartphone. The principle of detection in this innovative sensing platform was based on the chemical interactions of these metal ions with specific reagents. These interactions produced striking observable color changes that allowed for the easy identification and quantification of these targets in complex matrices. Based on the smartphone-supported digital image analysis, the prepared sensor enabled quantitative detection with linear detection ranges of 0.1 to 80 mM, 3 nM to 2 µM, and 1 to 60 mM for Cu(ii), Cr(vi), and Ni(ii), respectively. In addition, the developed colorimetric sensor achieved lower limits of quantification of 0.1 mM, 3 nM, and 1 mM for Cu(ii), Cr(vi), and Ni(ii) ions, respectively. The sensor's performance was validated by its excellent selectivity against potential interfering ions and its successful application in the analysis of a real fish sample.