Voltammetric Method for Determining Ferric Ions with Quercetin

Abstract

A novel, simple, rapid, inexpensive, highly sensitive voltammetric method developed for determining ferric ions with quercetin in water samples and iron supplements using a disposable bare pencil graphite electrode is described. The limit of detection and analytical ranges for the ferric ions were 3.6 nM and 17.9–716.0 nM, respectively. The results with the water samples were compared with those obtained from a potentiometric auto‐titration system, and the method's accuracy was tested using certified reference material. The complex stoichiometry and electrode reaction were also systematically investigated with UV‐visible spectrophotometry, 1H‐NMR spectroscopy and voltammetry.

Signal-Enhanced Electrochemical Determination of Quercetin with Poly(chromotrope fb)-Modified Pencil Graphite Electrode in Vegetables and Fruits

“…The typical plot of E p (V) versus log­( v , V/s) was drawn to calculate the apparent charge-transfer coefficient (α) (Figure S8). The slope of E p = 0.0511 log­( v ) + 0.2136 ( R 2 : 0.959) was equal to 2.3 RT /[(1 – α) nF ], and α was found as 0.42, thereby depicting how the transition state acted uniformly between the responses of Qn and Qn- O -quinone against the applied potential …”

“…The slope of E p = 0.0511 log(v) + 0.2136 (R 2 : 0.959) was equal to 2.3RT/[(1 − α)nF], and α was found as 0.42, thereby depicting how the transition state acted uniformly between the responses of Qn and Qn-O-quinone against the applied potential. 20 The ratio of proton to electron was calculated as 1 from the E p −pH curve having a slope of −68.6 mV/pH (Figure S9). This coincides with the oxidation of Qn including the 2electron and 2-proton process reported in the literature (Figure 1A).…”

“…The methods based on spectrophotometry , and chromatography , are widely used for determining Qn. Although these methods yield in terms of sensitivity and selectivity, they employ labor-intensive pretreatment steps, difficult separation procedures, and sophisticated and expensive instruments. , In recent years, electrochemical sensors have come to the forefront for determining some electroactive food and biologically essential substances. − Due to some distinct features of electrochemical methods such as being simple, quick, portable, cost-effective, sensitive, and selective, they have become one of the most encouraging methods for determining Qn. , A wide variety of modified electrodes including single- or multipolymer film-modified electrodes with or without metal nanoparticles, − carbon nanotube-based electrodes with or without polymer films, , molecularly imprinted polymer (MIP)-based electrodes, , and the other ones , have been reported for the determination of Qn, and they are summarized in Table S1. The electrodes composed of a single polymer , have high limit of detection (LOD) values (i.e., 0.17 and 20 μM); the other electrodes have complex and time-consuming preparation steps, ,,− and the supporting surfaces in these studies, i.e., glassy carbon electrodes (GCEs), carbon paste electrodes (CPEs), and paraffin-impregnated graphite disk electrode, have advantages such as being prone to electrocatalysis, resistant to surface contamination, and undesired electrode reactions. − However, they have disadvantages due to being expensive, nondisposable, and requiring pretreatment.…”

“…The electrodes composed of a single polymer , have high limit of detection (LOD) values (i.e., 0.17 and 20 μM); the other electrodes have complex and time-consuming preparation steps, ,,− and the supporting surfaces in these studies, i.e., glassy carbon electrodes (GCEs), carbon paste electrodes (CPEs), and paraffin-impregnated graphite disk electrode, have advantages such as being prone to electrocatalysis, resistant to surface contamination, and undesired electrode reactions. − However, they have disadvantages due to being expensive, nondisposable, and requiring pretreatment. On the other hand, pencil graphite electrodes (PGEs) have some benefits involving cheapness, common technology, good electrochemical reactivity and mechanical endurance, and being disposable, commercially available, renewable, and suitable for modification. ,,, It has been reported that the polymer formed as a result of the uniform arrangement of azo dyes containing a hydroxyl group in the ortho position to the azoic group forms a stable redox-active layer, increases the electrode active surface area, and has an electrocatalytic effect toward the oxidation of small organic molecules with adjacent hydroxyl groups such as dopamine, ascorbic acid, and uric acid. , In view of these findings, a novel electrochemical sensing platform based on poly­(chromotrope fb)-modified activated pencil graphite electrode (pCFB/aPGE) that overcomes the mentioned limitations was produced for the determination of Qn in vegetables and fruits. Additionally, this is the first instance in which chromotrope fb (CFB) was electropolymerized.…”

“… 16 − 18 Due to some distinct features of electrochemical methods such as being simple, quick, portable, cost-effective, sensitive, and selective, they have become one of the most encouraging methods for determining Qn. 19 , 20 A wide variety of modified electrodes including single- or multipolymer film-modified electrodes with or without metal nanoparticles, 21 − 25 carbon nanotube-based electrodes with 26 or without polymer films, 27 , 28 molecularly imprinted polymer (MIP)-based electrodes, 29 , 30 and the other ones 31 , 32 have been reported for the determination of Qn, and they are summarized in Table S1 . The electrodes composed of a single polymer 21 , 24 have high limit of detection (LOD) values (i.e., 0.17 21 and 20 μM 24 ); the other electrodes have complex and time-consuming preparation steps, 22 , 23 , 25 − 32 and the supporting surfaces in these studies, i.e., glassy carbon electrodes (GCEs), carbon paste electrodes (CPEs), and paraffin-impregnated graphite disk electrode, have advantages such as being prone to electrocatalysis, resistant to surface contamination, and undesired electrode reactions.…”