Digital image determination of copper in food and water after preconcentration and magnetic tip separation for in-cavity desorption/color development

• Published in: Food chemistry Vol. 442; p. 138435
• Main Authors: Alharbi, Walaa, Alharbi, Khadijah H., Alotaibi, Abdullah A., Gomaa, Hassan E.M., Abdel Azeem, Sami M.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-06-2024
• Subjects: Copper; Digital-image based; Food; Magnetic adsorbent; Water; Magnetic adsorbent; Water; Copper; Digital-image based; Food
• ISSN: 0308-8146; 1873-7072
• DOI: 10.1016/j.foodchem.2024.138435

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•Novel approach of digital-image based method combined to SPE.•In-situ Cu(II) desorption and spot color development using iodide-starch reagent for DIB imaging.•Development of a new magnetic SPE adsorbent for copper preconcentration.•The method provided low detection limit sufficient for trace copper analysis in food and water.•An adsorbent with a more than fifteen-fold cycle life.
A new analytical method for measuring copper in food and water was developed and validated, employing a solid-phase extraction (SPE) technique combined with digital-image-based (DIB) detection. A novel magnetic adsorbent of zinc ferrite/Citrullus colocynthis biochar ([e-mail]) was used to preconcentrate copper. A magnetic tip was used to separate the copper-loaded adsorbent from the extraction medium and to dispense it to the DIB plate. In-situ desorption and development of the spot color with iodide-starch reagent were carried out, and a digital image of the developed spots was captured using a smartphone and processed using ImageJ software. The copper adsorption capacity was 91.3 mg g−1. Desorption was effected using a 0.3 mol L-1 hydrochloric acid. The preconcentration factor was 300, the limit of detection was 4.8 μg L-1, the linearity was 16–600 μg L-1 and the sample throughput was 12 h−1. The developed approach was validated by analyzing food and water samples, confirming recoveries ≥ 91 % and 88 %, respectively, with RSD ≤ 8.4 %, n = 3.