ImageJ analysis for quantifying lead ion in environmental water using gold nanoparticles as a colorimetric probe

• ImageJ analysis for the colorimetric determination of Pb(II). • Photograph images utilized obtain colour intensity. • Simple, rapid, efficient and accurate colorimetric probe. • Validation using conventional methods. This research showcases a novel colorimetric approach, supported by ImageJ software (computer application), for the quantification of lead ion (Pb(II)) levels in environmental water with gold nanoparticles (AuNPs) serving as the colorimetric probe. AuNPs were synthesized by chemically reducing gold(III) chloride trihydrate with trisodium citrate as a modifying agent to prevent particle aggregation, resulting in wine-red AuNPs suspensions. Transmission electron microscopy (TEM) and Ultraviolet–Visible spectroscopy (UV–Vis) were utilized to characterize the synthesized AuNPs. ImageJ software was employed for the colorimetric quantification of Pb(II) and it was observed that the colour intensity increased proportionally with the increase in Pb(II) concentration. The Pb(II) analytical performances were linear from 0.1 to 20 mg/L with a detection limit of 0.01 mg/L. The developed colorimetric probe yielded excellent selectivity towards Pb(II) against other competing cations such as zinc(II), copper(II), manganese(II), chromium(VI), nickel(II), and iron(II). Furthermore, river and tap water samples were spiked with 0.5, 10, 60, and 100 mg/L and yielded %recoveries between 93–99 % and 88–98 % for ImageJ and UV–Vis methods, respectively. The validity and accuracy of this ImageJ method were supported by the conventional UV–Vis spectrophotometric method which gave a detection limit of 0.12 mg/L over a linear range of 0.1–20 mg/L.