A colorimetric probe based on 4-mercaptophenol and thioglycolic acid-functionalized gold nanoparticles for determination
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ORIGINAL PAPER
A colorimetric probe based on 4-mercaptophenol and thioglycolic acid-functionalized gold nanoparticles for determination of phytic acid and Fe(III) ions Ömer Kaan Koç 1,2
&
Ayşem Üzer 2
&
Reşat Apak 2,3
Received: 26 February 2020 / Accepted: 4 August 2020 / Published online: 30 September 2020 # Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract As a first of its kind, we developed a highly sensitive colorimetric nanoprobe for phytic acid (PA) and Fe(III) ion detection based on 4-mercaptophenol (4MP) and thioglycolic acid (TGA)-functionalized gold nanoparticles {AuNPs@(4MP-TGA)}. AuNPs were easily derivatized by 4MP and TGA through –SH binding to gold. Fe(III) ions possibly are bound first to the phenolate groups of 4MP-AuNPs, and further coordinated several nanoparticles via the carboxylate groups of TGA-AuNPs to cause aggregation, resulting in a red-to-purple color change and a bathochromic shift in the SPR absorption band of the nanoprobe. With the addition of PA to the AuNPs@(4MP-TGA)-Fe(III) system, the aggregated particles were released due to strong complex formation between Fe(III) and PA, resulting in a restoration of the color (purple-to-red) and of the SPR band to the original 520 nm wavelength maximum. Thus, the 650-nm absorption is attenuated and the 520-nm band is enhanced upon PA-Fe(III) chelation. This means that the absorption ratio A650/A520 is an indication of Fe(III) whereas the reverse ratio A520/A650 of the PA content of complex samples. The limits of detection (LOD) of the AuNPs@(4MP-TGA) were 1.0 μM for Fe(III) ions and 0.15 μM for PA. Phytic acid extracted from bean grains was determined with the proposed probe, yielding good recoveries. In addition, common metal ions, anions, and several biomolecules did not show an adverse effect on the nanoprobe performance for ferric ions and phytate. The developed method was statistically validated against a LC–MS/MS literature method. Keywords Phytic acid (PA) . Colorimetric probe . Gold nanoparticles (AuNPs) . Fe(III) ions . Antioxidant . Spectrophotometric determination
Introduction Phytic acid (PA), known as inositol hexaphosphate, is present as the main storage form of phosphorus in cereal and legume Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00604-020-04478-2) contains supplementary material, which is available to authorized users. * Reşat Apak [email protected] 1
Institute of Graduate Studies, Istanbul University-Cerrahpaşa, 34320 Avcilar, Istanbul, Turkey
2
Department of Chemistry, Faculty of Engineering, Istanbul University-Cerrahpaşa, 34320 Avcilar, Istanbul, Turkey
3
Turkish Academy of Sciences (TUBA), Piyade St. No. 27, Çankaya, 06690 Ankara, Turkey
grains [1]. PA, a multilayer molecule, is a natural antioxidant and forms water-insoluble complexes with metal cations found in foods such as iron, calcium, copper, and zinc under physiological conditions [2]. Its antioxidant ability possibly arises from the sequestering of transition metal ions
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