Digital image-based method for iron detection using green tea (Camellia sinensis) extract as natural colorimetric reagent

Ballesteros, Joel I.; Caleja-Ballesteros, Harriet Jane R.; Villena, Marte C.

doi:10.1016/j.microc.2020.105652

Cited by 26 publications

(15 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This new feature is the responsible for the strong color change observed in the interaction of Fe 3+ with phenolic compounds. The new broad band appearing at longer wavelength is attributed to the ligand-to-metal charge transfer (LMCT) from the polyphenol to the Fe 3+ center of the complex. , It is interesting to note that the maximum of this new band undergoes a blueshift from 580 to 552 nm upon increasing the pH to 11 in both GA and TA. This shift is likely due to the polyphenol autoxidation at alkaline pH, giving rise to quinone structures as well as oligomerization of polyphenols promoted at alkaline pH. , However, a change in the interaction stoichiometry of the ligand with the Fe 3+ after OH group ionization can also account for this shift .…”

Section: Resultsmentioning

confidence: 99%

“…For this reason, the ultraviolet absorption of iron–phenolic acid complexes is quite different from Fe(OH) 6 3– . This is an important fact that is related to the specific structure of polyphenols when complexed by metals, which in turn also depends on the number of ligands surrounding the metal sphere of coordination . Also, this effect can serve to establish a correlation between the UV–vis absorption spectrum and the structure.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Analysis of Iron Complexes of Tannic Acid and Other Related Polyphenols as Revealed by Spectroscopic Techniques: Implications in the Identification and Characterization of Iron Gall Inks in Historical Manuscripts

et al. 2022

View full text Add to dashboard Cite

In this work, a structural analysis of the polyphenol complexes with iron and copper at several conditions is reported. The investigated polyphenols were tannic acid, gallic acid, pyrogallol, and syringic acid, being components and molecular models of the gallnuts usually employed in the past in fabrication of iron gall inks (IGIs). Commercial tannic acid extracted from gallnuts, which is a complex mixture of different gallotannins and simpler galloylglucoses, was also employed in this analysis. This analysis comprised the use of Raman, Fourier-transform infrared (FTIR), UV–vis absorption, and fluorescence spectroscopy. The complexation of iron with these molecules leads to a strong change in color due to the deep restructuring of the polyphenol that can be clearly seen by Raman and FTIR spectra. Three main Raman bands appeared at 1450–1490 cm –1 (ν 1 ), 1320–1345 cm –1 (ν 2 ), and 400–650 cm –1 (ν 3 ), which are characteristic of the metal complexes. The structural changes of the polyphenol complexes with iron were also investigated at different pHs and different polyphenol/iron stoichiometries. Other effects of the interaction of polyphenols with iron are the pH decrease of the mixture upon metal complexation and fluorescence quenching induced by the interaction of iron. This quenching is important since it facilitates the Raman inspection of manuscripts since polyphenols show a strong fluorescence emission that overlaps the Raman spectrum. Furthermore, DFT calculations were performed for the first time on the gallic acid complex with iron in order to elaborate a detailed assignment of the vibrational modes of polyphenols and their metal complexes, something that was missed in previous applications of Raman to IGIs.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Analysis of Iron Complexes of Tannic Acid and Other Related Polyphenols as Revealed by Spectroscopic Techniques: Implications in the Identification and Characterization of Iron Gall Inks in Historical Manuscripts

et al. 2022

View full text Add to dashboard Cite

show abstract

“…Fe 3+ reacts with gallic acid forming a violet complex. The color developed is due to the ligand-to-metal charge transfer from the polyphenol to the iron center of the complex …”

Section: Resultsmentioning

confidence: 99%

“…Iron was quantified in water and dietary supplements , using green tea as the chromogenic reagent, where the gallic acid present in green tea was responsible for color development. In these studies, the violet-colored complexes had their λ max values in the 550–570 nm range.…”

Section: Resultsmentioning

confidence: 99%

“…Several methods have been developed for the determination of iron in dietary supplements such as atomic absorption spectrometry, voltammetry, fluorescence, inductively coupled plasma spectrometry, and X-ray fluorescence. 15 However, expensive instrumentation is needed using these methods, and an alternative for these methods is digital image colorimetry, which also offers low-cost and portable analysis.…”

Section: T H Imentioning

confidence: 99%

See 1 more Smart Citation

Iron Quantification in Dietary Supplements using Four Colorimetric Assays

Filgueiras

Borges

2022

J. Chem. Educ.

View full text Add to dashboard Cite

Students determine the iron mass in dietary supplements using four colorimetric assays. These colorimetric assays were selective for Fe3+. It was complexed by thiocyanide, salicylate, gallic acid, and Fe(CN)6 4–, forming blood-red, red, violet, and blue complexes, respectively. The λmax of these complexes were 447, 480, 570, and 700 nm, respectively. These assays were scaled-down, where 1 mL of chromogenic reagent was mixed with 0.1 mL of sample. Salicylic acid, gallic acid, and K4[Fe(CN)6] were harmless and cheap chromogenic reagents that could be used instead of traditional chromogenic reagents such as KSCN and phenanthroline. Quantitative analysis was carried out using absorbance measured at λmax of each assay (standard method) and 96-well-plate digital images obtained with a desktop scanner (proposed method). The matrix effect was investigated by comparing the standard addition curves with the external calibration curves, where no matrix effect was found. Results obtained using the four assays were compared using hypothesis tests such as one-way ANOVA, post-hoc tests, and plots. Investigation of interactions between samples and assays was carried out using two-way ANOVA. Statistical tests were carried out using open-source and graphical user interface programs (JASP and R Commander). The student learning goals of this experiment include comparing multiple assays using hypothesis tests. Learn about the principles of green chemistry, method scale-down, and matrix effect.

show abstract

Green synthesis of iron nanoparticles using mulberry leaf extract: characterization, identification of active biomolecules, and catalytic activity

Wang,

Zhang,

Liu

et al. 2024

Environ Sci Pollut Res

View full text Add to dashboard Cite

Digital image-based method for iron detection using green tea (Camellia sinensis) extract as natural colorimetric reagent

Cited by 26 publications

References 34 publications

Analysis of Iron Complexes of Tannic Acid and Other Related Polyphenols as Revealed by Spectroscopic Techniques: Implications in the Identification and Characterization of Iron Gall Inks in Historical Manuscripts

Analysis of Iron Complexes of Tannic Acid and Other Related Polyphenols as Revealed by Spectroscopic Techniques: Implications in the Identification and Characterization of Iron Gall Inks in Historical Manuscripts

Iron Quantification in Dietary Supplements using Four Colorimetric Assays

Green synthesis of iron nanoparticles using mulberry leaf extract: characterization, identification of active biomolecules, and catalytic activity

Contact Info

Product

Resources

About