The Development of a Selective Colorimetric Sensor for Cu<sup>2+</sup> and Zn<sup>2+</sup> in Mineral Supplement with Application of a Smartphone Paper-Based Assay of Cu<sup>2+</sup> in Water Samples

The Development of a Selective Colorimetric Sensor for Cu<sup>2+</sup> and Zn<sup>2+</sup> in Mineral Supplement with Application of a Smartphone Paper-Based Assay of Cu<sup>2+</sup> in Water Samples

Herein, we developed a colorimetric method for the determination of Cu<sup>2+</sup> and Zn<sup>2+</sup> using NBD-G as a novel selective metal sensor. NBD-G was easily synthesized by a nucleophilic substitution reaction between 4-chloro-7-nitro-2,1,3-benzoxadiazole (NBD-Cl) a...

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Bibliographic Details
Main Authors: Mahmoud El-Maghrabey, Shōta Seino, Naoya Kishikawa, Naotaka Kuroda
Format: Article
Language:English
Published: MDPI AG 2024-12-01
Series:Sensors
Subjects:
copper(II)
zinc(II)
NBD-Cl
Girard’s Reagent P
paper-based assay
mineral supplements
Online Access:https://www.mdpi.com/1424-8220/24/23/7844
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Summary:Herein, we developed a colorimetric method for the determination of Cu<sup>2+</sup> and Zn<sup>2+</sup> using NBD-G as a novel selective metal sensor. NBD-G was easily synthesized by a nucleophilic substitution reaction between 4-chloro-7-nitro-2,1,3-benzoxadiazole (NBD-Cl) and Girard’s Reagent P. The NBD-G solution is yellow, but when it reacts with Cu<sup>2+</sup> and Zn<sup>2+</sup>, its color changes selectively to red (510 nm) and orange (480 nm), respectively. NBD-G was used as a sensor for Cu<sup>2+</sup> and Zn<sup>2+</sup>, showing a high sensitivity down to 0.77 µM for Cu<sup>2+</sup> and 1.66 µM for Zn<sup>2+</sup>. NBD-G could determine both metals simultaneously; thus, it was applied to determine them in multimineral supplements, which showed excellent recoveries. Next, a filter paper impregnated with NBD-G was prepared as a test paper, and a simple, selective, and rapid onsite method for quantifying Cu<sup>2+</sup> was developed as, interestingly, the paper showed no change upon the addition of Zn<sup>2+</sup>. Next, Cu<sup>2+</sup> could be quantified with high selectivity and accuracy by photographing the color change with a smartphone camera and processing the image with Image J. The detection limit for Cu<sup>2+</sup> using this method was 3.9 µM. Finally, the NBD-G test paper method was able to satisfactorily quantify Cu<sup>2+</sup> spiked into the rainwater.
ISSN:1424-8220

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