Determination of Total Phenolic Compounds in Common Beverages Using CdTe Quantum Dots

Abstract

In this study, we describe a method of total phenolic compounds determination based on CdTe quantum dot (QD) fluorescence recovery in the presence of analyte. Polyphenols present in the solution were reducing agents, acting as electron donors to the CdTe–sodium periodate system, thus leading to perturbation of the transfer of excited electrons from QD to the acceptor molecules occurring in the absence of polyphenols. Using the developed technique the polyphenol content in green tea, black tea, Pu‐Erh tea, lemon balm, peppermint, lime, chamomile, and coffee infusions was successfully determined. The limit of detection of the method amounted to 0.63 nM of (+)‐catechin equivalent, which makes this technique nearly one order of magnitude more sensitive than the commonly used Folin–Ciocalteu method. Additionally, lack of impact of interference from proteins and reducing sugars on the results makes this technique an advantageous alternative to the Folin–Ciocalteu assay. Practical Applications The developed method for total phenolic compound determination, thanks to higher specificity and a low detection limit may be a beneficial alternative to the popular Folin–Ciocalteu assay. The applications of the described technique include plant raw material and product nutritional quality assessment as well as studying the effects of a polyphenol‐rich diet on human health. The assay is easy to use both in industry laboratories as well as in research and development.

Nanomaterial-Based Sensing and Biosensing of Phenolic Compounds and Related Antioxidant Capacity in Food

“…When tested vs. different antioxidant molecules, intensity of the color response was observed in this order: catechin, gallic acid > caffeic acid > ascorbic acid > coumaric acid > vanillic acid > ferulic acid > cinnamic acid. This is in agreement with the antioxidant polyphenols classical reactivity (i.e., flavonoids > o -phenol > m -phenols) [ 41 , 43 , 60 ]. Antioxidant activity of tea and wine samples was assessed expressing the data as gallic acid equivalents and using visual inspection by a digital camera.…”

“…No comparison with existing methods was reported. CdTe QDs fluorescence recovery in the presence of the analyte was proposed by Dwiecki et al [ 60 ]. Polyphenols acted as electron donors for the CdTe–sodium periodate system, leading to perturbation of the transfer of excited electrons from QD to the acceptor molecules occurring in the absence of polyphenols.…”

An Overview of Optical and Electrochemical Sensors and Biosensors for Analysis of Antioxidants in Food during the Last 5 Years

“…In biological applications, QDs as well as fluorophores have become important [ 66 ], because of the possibility to size-tune fluorescent emissions as a consequence of the core size, shape and material [ 22 ]. Dwiecki et al, suggested an approach for total phenolic compounds identification of common drinks (tea and coffee) based on CdTe QDs fluorescence in the presence of an analyte [ 67 ]. Polyphenols acted as reducing agents with the ability to transfer electrons to the CdTe-sodium periodate system leading to perturbation of the conduction of excited electrons from QD to the acceptor molecules happening in the absence of polyphenols.…”

Measurement of antioxidants in distilled spirits by a silver nanoparticle assay

“…Recent interest in utilizing metal nanoparticle (NP) assays for determination of TAC in food and plant extract samples has been growing . Many of these NP assays have been validated against other methods, including the Folin–Ciocalteu assay or CUPRAC assay and one gold nanoparticle assay has been validated with quantitative HPLC measurements . Özyürek et al .…”

“…Recent interest in utilizing metal nanoparticle (NP) assays for determination of TAC in food and plant extract samples has been growing (16)(17)(18)(19)(20)(21). Many of these NP assays have been validated against other methods, including the Folin-Ciocalteu assay (19) or CUPRAC assay (17,18) and one gold nanoparticle assay has been validated with quantitative HPLC measurements (21). Özyürek et al (17) provided an excellent report of a developed and validated silver nanoparticle antioxidant capacity (SNPAC) assay for the measurement of the antioxidant capacity of polyphenols.…”