Evaluation of total polyphenol content of wines by means of voltammetric techniques: Cyclic voltammetry vs differential pulse voltammetry

Rapid determination of geographical authenticity and pungency intensity of the red Sichuan pepper (Zanthoxylum bungeanum) using differential pulse voltammetry and machine learning algorithms

The development of an analytical method for assessing pungency intensity and determining geographical origins is crucial for evaluating the quality of visually similar Zanthoxylum bungeanum pericarp (PZB). This study analyzed 210 PZB samples from 14 origins across China, focusing on origin adulteration identification and pungency intensity using a combination of differential pulse voltammetry (DPV) and machine learning algorithms. The artificial neural network (ANN) and K-nearest neighbor (KNN) algorithms provided the highest accuracy in origin identification (100 %) and adulteration detection (97.9 %) respectively. Moreover, the ANN excelled in predicting pungency intensity (R2 = 0.918). Assessment via feature importance analysis of DPV features revealed that segments of polyphenols (0.34-0.52 V and 1.0-1.2 V) and alkylamides (1.0-1.2 V) contributed significantly to the PZB pungency intensity. These findings highlight the potential of DPV as a reliable method for assessing the quality of PZB, and offer a promising solution for ensuring the geographical authenticity of this important crop.

An electrochemical biosensor based on phage-encoded protein RBP 41 for rapid and sensitive detection of Salmonella

Salmonellosis caused by Salmonella contaminated food poses a serious threat to human health. The rapid and accurate detection of Salmonella is critical for preventing foodborne illness outbreaks. In this study, an electrochemical biosensor was developed using a newly identified biorecognition element, RBP 41, which is capable of specifically recognizing and binding to Salmonella. The biosensor was constructed through a layer-by-layer assembly of graphene oxide (GO), gold nanoparticles (GNPs), and RBP 41 on a glassy carbon electrode (GCE), with the GNPs amplifying the detection signal. The established biosensor was able to detect Salmonella in concentrations ranging from 3 to 106 CFU/mL within approximately 30 min by using differential pulse voltammetry (DPV) signal, and the estimated detection limit was to be 0.2984 Log10 CFU/mL. The biosensor demonstrated excellent specificity and was effective in detecting Salmonella in food matrices, such as skim milk and lettuce. Overall, this study highlights the potential of phage tail receptor binding proteins in biosensing and the proposed biosensor as a promising alternative for rapid and sensitive Salmonella detection in various samples.

A highly selective and sensitive electrochemical sensor for tetracycline resistant genes detection based on the non-covalent interaction of graphene oxide and nucleobase

Antibiotic resistance genes (ARGs) are causing worldwide environmental problems, however, the traditional analytical methods and test equipment for them are time-consuming and expensive. The electrochemical sensor using the non-covalent bond between graphene oxide (GO) and single-stranded tet (ss-tet) was established for specific tetracycline resistance genes (tet, composed of ss-tet and complementary ss-tet (ss-tet') in water) detection, which preparation time was only 35 min and far less than most reported sensors based on covalent bond. As the result of the detection for tet, the developed sensor not only had the low detection limit of 50.0 pM (8.1 × 102 copies·mL-1), the short detection time within 42 min, but also had satisfactory stability, excellent reproducibility, and highly selectivity (RSD < 4.43 %). Besides, it also had acceptable accuracy comparing to the real-time quantitative polymerase chain reaction (RT-qPCR) and PCR array in tet detection. Noticeably, it also had been successfully applied to tetA detection in different water samples. In brief, the prepared non-covalent bond sensor is simple, rapid, and suitable for highly selective and sensitive detection of the ARGs in actual water.

White wine phenolics: current methods of analysis

White wine phenolic analyses are less common in the literature than analyses of red wine phenolics. Analytical techniques for white wine phenolic analyses using spectrophotometric, chromatographic, spectroscopic, and electrochemical methods are reported. The interest of research in this area combined with the advances in technology aimed at the winemaking industry are promoting the establishment of novel approaches for identifying, quantifying, and classifying phenolic compounds in white wine. This review article provides an overview of the current research into white wine phenolics through a critical discussion of the analytical methods employed. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Development of a new paper-based voltage step electrocoagulation technique and application to wine classification

This study developed a novel voltage step electrocoagulation (VSEC) technique on paper for analysis and classification of red wine samples. The concept relies on the electrode system applying voltage steps along a strip of filter paper soaked with a wine sample. The system employed a cathode array system (CAS) for voltage step application and an aluminium anode undergoing corrosion to form the green sludges responsible for wine color bleaching along the paper. The VSEC technique led to the shade of colors along the paper which can be observed by the naked-eye or using image processing software. The system was applied to classify 15 wine samples into different groups and to perform dilution and adulteration tests. In addition, the approach could be applied to approximate antioxidant properties of the wine samples as observed via the correlation between the results from VSEC and IC₅₀ values obtained from the DPPH assay with an R² of 0.76.

Electrospun nanofiber-based glucose sensors for glucose detection

Diabetes is a chronic, systemic metabolic disease that leads to multiple complications, even death. Meanwhile, the number of people with diabetes worldwide is increasing year by year. Sensors play an important role in the development of biomedical devices. The development of efficient, stable, and inexpensive glucose sensors for the continuous monitoring of blood glucose levels has received widespread attention because they can provide reliable data for diabetes prevention and diagnosis. Electrospun nanofibers are new kinds of functional nanocomposites that show incredible capabilities for high-level biosensing. This article reviews glucose sensors based on electrospun nanofibers. The principles of the glucose sensor, the types of glucose measurement, and the glucose detection methods are briefly discussed. The principle of electrospinning and its applications and advantages in glucose sensors are then introduced. This article provides a comprehensive summary of the applications and advantages of polymers and nanomaterials in electrospun nanofiber-based glucose sensors. The relevant applications and comparisons of enzymatic and non-enzymatic nanofiber-based glucose sensors are discussed in detail. The main advantages and disadvantages of glucose sensors based on electrospun nanofibers are evaluated, and some solutions are proposed. Finally, potential commercial development and improved methods for glucose sensors based on electrospinning nanofibers are discussed.

Distinctive Features of Composts of Different Origin: A Thorough Examination of the Characterization Results

The potential of composts produced from different origin residues to be used in environmentally friendly agriculture is addressed in this work. Seven composts obtained from different raw materials and composting methodologies are compared using elemental, thermal and spectroscopic characterization data. Despite the stabilization of the organic matter in all composts being adequate for agricultural applications, they display distinct elemental and structural compositions. Likewise, the fertilisers have very different effects on lettuce growth. Despite the observed differences, some common features were found, namely a mass loss (TGA) of 25.2 g per mol C, association between groups of elements (Fe, Al, Ni, Co, Cr, Cu and S; Mg, Na, K and P, C, Coxi, N and Pb) and correlations between the amount of carbon nanostructures and the characteristic aromaticity parameters. These results suggest that the tuning of the compost features for specific cultures may be possible for sustainable food production.

A single screen-printed electrode in tandem with chemometric tools for the forensic differentiation of Brazilian beers

In the present study a single screen-printed carbon electrode (SPCE) and chemometric techniques were utilized for forensic differentiation of Brazilian American lager beers. To differentiate Brazilian beers at the manufacturer and brand level, the classification techniques: soft independent modeling of class analogy (SIMCA), partial least squares regression discriminant analysis (PLS-DA), and support vector machines discriminant analysis (SVM-DA) were tested. PLS-DA model presented an inconclusive assignment ratio of 20%. On the other hand, SIMCA models had a 0 inconclusive rate but an sensitivity close to 85%. While the non-linear technique (SVM-DA) showed an accuracy of 98%, with 95% sensitivity and 98% specificity. The SPCE-SVM-DA technique was then used to distinguish at brand level two highly frauded beers. The SPCE coupled with SVM-DA performed with an accuracy of 97% for the classification of both brands. Therefore, the proposed electrochemicalsensor configuration has been deemed an appropriate tool for discrimination of American lager beers according to their producer and brands.

Differential pulse voltammetry and chronoamperometry as analytical tools for epinephrine detection using a tyrosinase-based electrochemical biosensor

The main goal of the presented study was to design a biosensor-based system for epinephrine (EP) detection using a poly-thiophene derivative and tyrosinase as a biorecognition element. We compared two different electroanalytical techniques to select the most prominent technique for analyzing the neurotransmitter. The prepared biosensor system exhibited good parameters; the differential pulse (DPV) technique presented a wide linear range (1–20 μM and 30–200 μM), with a low detection limit (0.18 nM and 1.03 nM). In the case of chronoamperometry (CA), a high signal-to-noise ratio and lower reproducibility were observed, causing a less broad linear range (10–200 μM) and a higher detection limit (125 nM). Therefore, the DPV technique was used for the calculation of sensitivity (0.0011 μA mM⁻¹ cm⁻²), stability (49 days), and total surface coverage (4.18 × 10⁻¹² mol cm⁻²). The biosensor also showed very high selectivity in the presence of common interfering species (i.e. ascorbic acid, uric acid, norepinephrine, dopamine) and was successfully applied for EP determination in a pharmaceutical sample.

GCE/poly-4,4′-bBT/tyrosinase biosensor for epinephrine was constructed. Comparison of differential pulse voltammetry (DPV) and chronoamperometry was performed. DPV showed more reproducible results giving high selectivity, sensitivity, stability.

Rapid Determination of the 'Legal Highs' 4-MMC and 4-MEC by Spectroelectrochemistry: Simultaneous Cyclic Voltammetry and In Situ Surface-Enhanced Raman Spectroscopy

The synthetic cathinones mephedrone (4-MMC) and 4-methylethcathinone (4-MEC) are two designer drugs that represent the rise and fall effect of this drug category within the stimulants market and are still available in several countries around the world. As a result, the qualitative and quantitative determination of 'legal highs', and their mixtures, are of great interest. This work explores for the first time the spectroelectrochemical response of these substances by coupling cyclic voltammetry (CV) with Raman spectroscopy in a portable instrument. It was found that the stimulants exhibit a voltammetric response on a gold screen-printed electrode while the surface is simultaneously electro-activated to achieve a periodic surface-enhanced Raman spectroscopy (SERS) substrate with high reproducibility. The proposed method enables a rapid and reliable determination in which both substances can be selectively analyzed through the oxidation waves of the molecules and the characteristic bands of the electrochemical SERS (EC-SERS) spectra. The feasibility and applicability of the method were assessed in simulated seized drug samples and spiked synthetic urine. This time-resolved spectroelectrochemical technique provides a cost-effective and user-friendly tool for onsite screening of synthetic stimulants in matrices with low concentration analytes for forensic applications.

Red Wine Oxidation Characterization by Accelerated Ageing Tests and Cyclic Voltammetry

In order to obtain information on the oxidative behavior of red wines, oxygen consumption rates and electrochemical changes (cyclic voltammetry) were measured for nine red wines subject to three different accelerated ageing tests: chemical (with hydrogen peroxide), enzymatic (with laccase from Trametes versicolor), and temperature (at 60 °C). Oxidative behavior depended both on the wine sample and accelerated ageing test type. A good correlation was observed between electrochemical parameters of charges for reference/non-oxidized wines, in accordance with their antioxidant capacity, and the variation of charges after enzymatic and temperature tests, meaning that cyclic voltammetry could be used in order to predict these two oxidation tests and reflect the wine sensitivity towards respective oxidation targets. However, it was not possible to predict wine chemical oxidation test based on hydrogen peroxide from the electrochemical measurements.

An assessment of voltammetry on disposable screen printed electrodes to predict wine chemical composition and oxygen consumption rates

The present work aimed at determining the applicability of linear sweep voltammetry coupled to disposable carbon paste electrodes to predict chemical composition and wine oxygen consumption rates (OCR) by PLS-modeling of the voltammetric signal. Voltammetric signals were acquired in a set of 16 red commercial wines. Samples were extensively characterized including SO₂, antioxidant indexes, metals and polyphenols measured by HPLC. Wine OCRs were calculated by measuring oxygen consumption under controlled oxidation conditions. PLS-Regression models were calculated to predict chemical variables and wine OCRs from first order difference voltammogram curves. A significant number of fully validated models predicting chemical variables from voltammetric signals were obtained. Interestingly, monomeric and polymerized anthocyanins can be differently predicted from the first and second wave of the first derivative of voltammograms, respectively. This fast, cheap and easy-to-use approach presents an important potential to be used in wineries for rapid wine chemical characterization.

Graphene-Assisted Sensor for Rapid Detection of Antibiotic Resistance in Escherichia coli

In recent years, antibiotic-resistant bacteria caused by antibiotic abuse in the medical industry have become a new environmental pollutant that endangers public health. Therefore, it is necessary to establish a detection method for evaluating drug-resistant bacteria. In this work, we used Escherichia coli as a target model and proposed a method to evaluate its drug resistance for three antibiotics. Graphene dispersion was used to co-mix with E. coli cells for the purpose of increasing the current signal. This electrochemical-based sensor allows the evaluation of the activity of E. coli on the electrode surface. When antibiotics were present, the electrocatalytic reduction signal was diminished because of the reduced activity of E. coli. Based on the difference in the electrochemical reduction signal, we can evaluate the antibiotic resistance of different E. coli strains.

Recent Advances in CRP Biosensor Based on Electrical, Electrochemical and Optical Methods

C-reactive protein (CRP) is an acute-phase reactive protein that appears in the bloodstream in response to inflammatory cytokines such as interleukin-6 produced by adipocytes and macrophages during the acute phase of the inflammatory/infectious process. CRP measurement is widely used as a representative acute and chronic inflammatory disease marker. With the development of diagnostic techniques measuring CRP more precisely than before, CRP is being used not only as a traditional biomarker but also as a biomarker for various diseases. The existing commercialized CRP assays are dominated by enzyme-linked immunosorbent assay (ELISA). ELISA has high selectivity and sensitivity, but its limitations include requiring complex analytic processes, long analysis times, and professional manpower. To overcome these problems, nanobiotechnology is able to provide alternative diagnostic tools. By introducing the nanobio hybrid material to the CRP biosensors, CRP can be measured more quickly and accurately, and highly sensitive biosensors can be used as portable devices. In this review, we discuss the recent advancements in electrochemical, electricity, and spectroscopy-based CRP biosensors composed of biomaterial and nanomaterial hybrids.

CuBi2O4 Synthesis, Characterization, and Application in Sensitive Amperometric/Voltammetric Detection of Amoxicillin in Aqueous Solutions

CuBi₂O₄ synthesized by thermolysis of a new Bi(III)-Cu(II) oxalate coordination compound, namely Bi₂Cu(C₂O₄)₄·0.25H₂O, was tested through its integration within carbon nanofiber paste electrode, namely CuBi/carbon nanofiber (CNF), for the electrochemical detection of amoxicillin (AMX) in the aqueous solution. Thermal analysis and IR spectroscopy were used to characterize a CuBi₂O₄ precursor to optimize the synthesis conditions. The copper bismuth oxide obtained after a heating treatment of the precursor at 700 °C/1 h was investigated by an X-ray diffraction and scanning electron microscopy. The electrochemical behavior of CuBi/CNF in comparison with CNF paste electrode showed the electrocatalytic activity of CuBi₂O₄ toward amoxicillin detection. Two potential detections, with one at the potential value of +0.540 V/saturated calomel electrode (SCE) and the other at the potential value of −1.000 V/SCE, were identified by cyclic voltammetry, which were exploited to develop the enhanced voltammetric and/or amperometric detection protocols. Better electroanalytical performance for AMX detection was achieved for CuBi/CNF using differential-pulsed and square-wave voltammetries than others reported in the literature. Very nice results obtained through anodic and cathodic currents recorded at +0.750 V/SCE and −1.000 V/SCE in the same time period using a pseudo multiple-pulsed amperometry technique showed the great potential of the CuBi/CNF paste electrode for practical applications in amoxicillin detection in aqueous solutions.

The Importance of Developing Electrochemical Sensors Based on Molecularly Imprinted Polymers for a Rapid Detection of Antioxidants

This review aims to pin out the importance of developing a technique for rapid detection of antioxidants, based on molecular imprinting techniques. It covers three major areas that have made great progress over the years in the field of research, namely: antioxidants characterization, molecular imprinting and electrochemistry, alone or combined. It also reveals the importance of bringing these three areas together for a good evaluation of antioxidants in a simple or complex medium, based on selectivity and specificity. Although numerous studies have associated antioxidants with molecular imprinting, or antioxidants with electrochemistry, but even electrochemistry with molecular imprinting to valorize different compounds, the growing prominence of antioxidants in the food, medical, and paramedical sectors deserves to combine the three areas, which may lead to innovative industrial applications with satisfactory results for both manufacturers and consumers.

Studying the preparation, electrochemical performance testing, comparison and application of a cost-effective flexible graphene working electrode

-A cost-effective flexible graphene working electrode (FGWE) was fabricated using overhead projector transparent film (OPTF) and a screen-printing technique. The surface morphology and electrochemical behavior of the electrode were characterized by scanning electron microscopy and cyclic voltammetry. The electrode presented a very thin layer of conductive ink (16.0 ± 0.7 µm) on a large effective surface area (0.301 ± 0.001 cm^-2). The anodic peak current density (j_pa) of acetaminophen (ACT) in FGWE was 5.2, 3.7, 3.5 and 6.0 times greater than the j_pa of glassy carbon electrode (GCE), flexible carbon working electrode (FCWE), SPE1, and SPE2, respectively. The electrochemical performance of FGWE toward ACT was evaluated by differential pulse voltammetry. Under optimized condition, ACT was quantified in a range of  4-100 µM, with good sensitivity, good accuracy (recovery = 82.3 ± 0.4 to 106 ± 3%), and excellent precision. FGWE was applied to determine ACT in commercial pharmaceutical formulations. The results of the study are in good agreement with those obtained by the standard spectrophotometric method. These results indicate that disposable FGWE is particularly useful for the detection of ACT, and its performance may serve as a platform for cost-effective flexible electrochemical sensors.

Nanomaterials Based Electrochemical Sensors for Serotonin Detection: A Review

The present review deals with the recent progress made in the field of the electrochemical detection of serotonin by means of electrochemical sensors based on various nanomaterials incorporated in the sensitive element. Due to the unique chemical and physical properties of these nanomaterials, it was possible to develop sensitive electrochemical sensors with excellent analytical performances, useful in the practice. The main electrochemical sensors used in serotonin detection are based on carbon electrodes modified with carbon nanotubes and various materials, such as benzofuran, polyalizarin red-S, poly(L-arginine), Nafion/Ni(OH)2, or graphene oxide, incorporating silver-silver selenite nanoparticles, as well as screen-printed electrodes modified with zinc oxide or aluminium oxide. Also, the review describes the nanocomposite sensors based on conductive polymers, tin oxide-tin sulphide, silver/polypyrole/copper oxide or a hybrid structure of cerium oxide-gold oxide nanofibers together with ruthenium oxide nanowires. The presentation focused on describing the sensitive materials, characterizing the sensors, the detection techniques, electroanalytical properties, validation and use of sensors in lab practice.

N-Way NIR Data Treatment through PARAFAC in the Evaluation of Protective Effect of Antioxidants in Soybean Oil

The use of chemometric tools is progressing to scientific areas where analytical chemistry is present, such as food science. In analytical food evaluation, oils represent an important field, allowing the exploration of the antioxidant effects of herbs and seeds. However, traditional methodologies have some drawbacks which must be overcome, such as being time-consuming, requiring sample preparation, the use of solvents/reagents, and the generation of toxic waste. The objective of this study is to evaluate the protective effect provided by plant-based substances (directly, or as extracts), including pumpkin seeds, poppy seeds, dehydrated goji berry, and Provençal herbs, against the oxidation of antioxidant-free soybean oil. Synthetic antioxidants tert-butylhydroquinone and butylated hydroxytoluene were also considered. The evaluation was made through thermal degradation of soybean oil at different temperatures, and near-infrared spectroscopy was employed in an n-way mode, coupled with Parallel Factor Analysis (PARAFAC) to extract nontrivial information. The results for PARAFAC indicated that factor 1 shows oxidation product information, while factor 2 presents results regarding the antioxidant effect. The plant-based extract was more effective in improving the frying stability of soybean oil. It was also possible to observe that while the oxidation product concentration increased, the antioxidant concentration decreased as the temperature increased. The proposed method is shown to be a simple and fast way to obtain information on the protective effects of antioxidant additives in edible oils, and has an encouraging potential for use in other applications.

Voltammetric Behavior, Flavanol and Anthocyanin Contents, and Antioxidant Capacity of Grape Skins and Seeds during Ripening (Vitis vinifera var. Merlot, Tannat, and Syrah)

Skin and seed grape extracts of three red varieties (Merlot, Tannat, and Syrah) at different stages of ripening were studied for their total phenolic content (TPC) by using the Folin-Ciocalteu assay and for their total antioxidant capacity (TAC) by using spectrophotometric and electrochemical assays. Flavanol and anthocyanin compositions were also investigated using Ultra Performance Liquid Chromatography coupled with Mass Spectrometry (UPLC-MS). Results showed that seeds had the highest phenolic content and the highest antioxidant potential compared to skins at all stages of ripening. The highest TPC and TAC values were measured in seeds at close to veraison and veraison ripening stages. In skins, the highest values were found at the green stage, it was in accordance with the flavanols content. The voltammetric measurements were carried out using disposable single walled carbon nanotubes modified screen-printed carbon electrodes (SWCNT-SPCE). Three peaks on voltammograms were obtained at different oxidation potentials. The first anodic peak that oxidized at a low potential describes the oxidation of ortho-dihydroxy phenols and gallate groups, the second peak corresponds to the malvidin anthocyanins oxidation and the second oxidation of flavonoids. The third voltammetric peak could be due to phenolic acids such as p-coumaric acid and ferulic acid or the second oxidation of malvidin anthocyanins. The high linear correlation was observed between antioxidant tests and flavanols in skins (0.86 ≤ r ≤ 0.94), while in seeds, 'r' was higher between electrochemical parameters and flavanols (0.64 ≤ r ≤ 0.8).

Sensorial Perception of Astringency: Oral Mechanisms and Current Analysis Methods

Understanding consumers' food choices and the psychological processes involved in their preferences is crucial to promote more mindful eating regulation and guide food design. Fortifying foods minimizing the oral dryness, rough, and puckering associated with many functional ingredients has been attracting interest in understanding oral astringency over the years. A variety of studies have explored the sensorial mechanisms and the food properties determining astringency perception. The present review provides a deeper understanding of astringency, a general view of the oral mechanisms involved, and the exciting variety of the latest methods used to direct and indirectly quantify and simulate the astringency perception and the specific mechanisms involved.

Electroactivity of polyphenols in sweet sorghum (Sorghum bicolor (L.) Moench) cultivars

Polyphenols and other potential health-promoting components of sorghum (Sorghum bicolor (L.) Moench) drove its recent growth in the U.S. consumer food industry. Linear sweep (cyclic voltammetry, CV) and differential (cyclic differential pulse) voltammetry methods were developed to detect target polyphenols and amino acids in sweet sorghum juice without interference from the dominant secondary (trans-aconitic acid) and primary (sucrose) metabolites. Of 24 cultivars investigated, No.5 Gambela showed the highest electron-donating capacity, as indicated by the highest peak area, height, and peak anodic potential. Pearson’s correlation analysis indicated the contribution of polyphenols (rather than amino acids) on CV voltammograms of juice samples. The E_h-pH values of 173 sweet sorghum juice samples collected in 2017 aligned with quercetin model polyphenol. Accumulation of quercetin-like polyphenols in No.5 Gambela could offer antioxidant-rich juice for conversion to edible syrup as well as an increased tolerance against a recently emerged pest, sugarcane aphid [(Melanaphis sacchari (Zehntner)].

Voltammetric Pathways for the Analysis of Ophthalmic Drugs

Background:

This review investigates the ophthalmic drugs that have been studied with voltammetry in the web of science database in the last 10 years.

Introduction:

Ophthalmic drugs are used in the diagnosis, evaluation and treatment of various ophthalmological diseases and conditions. A significant literature has emerged in recent years that investigates determination of these active compounds via electroanalytical methods, particularly voltammetry. Low cost, rapid determination, high availability, efficient sensitivity and simple application make voltammetry one of the most used methods for determining various kinds of drugs including ophthalmic ones.

Methods:

In this particular review, we searched the literature via the web of science database for ophthalmic drugs which are investigated with voltammetric techniques using the keywords of voltammetry, electrochemistry, determination and electroanalytical methods.

Results:

We found 33 types of pharmaceuticals in nearly 140 articles. We grouped them clinically into seven major groups as antibiotics, antivirals, non-steroidal anti-inflammatory drugs, anti-glaucomatous drugs, steroidal drugs, local anesthetics and miscellaneous. Voltammetric techniques, electrodes, optimum pHs, peak potentials, limit of detection values, limit of quantification values, linearity ranges, sample type and interference effects were compared.

Conclusion:

Ophthalmic drugs are widely used in the clinic and it is important to determine trace amounts of these species analytically. Voltammetry is a preferred method for its ease of use, high sensitivity, low cost, and high availability for the determination of ophthalmic drugs as well as many other medical drugs. The low limits of detection values indicate that voltammetry is quite sufficient for determining ophthalmic drugs in many media such as human serum, urine and ophthalmic eye drops.

Exploring the Antioxidant Features of Polyphenols by Spectroscopic and Electrochemical Methods

This paper evaluates the antioxidant ability of polyphenols as a function of their chemical structures. Several common food indexes including Folin-Ciocalteau (FC), ferric reducing antioxidant power (FRAP) and trolox equivalent antioxidant capacity (TEAC) assays were applied to selected polyphenols that differ in the number and position of hydroxyl groups. Voltammetric assays with screen-printed carbon electrodes were also recorded in the range of −0.2 to 0.9 V (vs. Ag/AgCl reference electrode) to investigate the oxidation behavior of these substances. Poor correlations among assays were obtained, meaning that the behavior of each compound varies in response to the different methods. However, we undertook a comprehensive study based on principal component analysis that evidenced clear patterns relating the structures of several compounds and their antioxidant activities.