Classical Spectrophotometric Methods Research Articles

Phenolic Class Analysis in Honey: Comparison of Classical and Single UV Spectrum Methodologies

The analytical results from a study of 16 honey samples (extra white to dark honey color range) of phenolic compounds obtained using the single UV spectrum methodology and classical spectrophotometric methods (Folin–Ciocalteu and AlCl3 methods) are presented. The first method quantified all classes of phenolic compounds in honey’s SPE-C18 extract: the total hydroxybenzoic acid content (concentrations between 0.37 ± 0.05 and 4.46 ± 0.37 mg of gallic acid/g of honey), total hydroxycinnamic acid content (0.13 ± 0.03 and 2.76 ± 0.13 mg of ferulic acid/g of honey), and total flavonoid content (0.15 ± 0.03 and 1.63 ± 0.17 mg of quercetin/g of honey). The total phenolic contents were, on average, 1.86 ± 0.72 and 1.78 ± 0.79 times higher than the results obtained for raw honey and the SPE-C18 extract, respectively, using the classical Folin–Ciocalteu method. The total flavonoid contents, on average, were 6.02 ± 3.14 times larger and 0.66 ± 0.33 times smaller than the results obtained using the classical AlCl3 method for raw honey and SPE-C18 extract, respectively.

State-of-the-art mathematically induced filtration approaches for smart spectrophotometric assessment of silodosin and solifenacin mixture in their new challenging formulation: Multi-tool greenness and whiteness evaluation

Benign prostatic hyperplasia is one of the most predominant health disorders in men with increasing incidence by age and usually accompanied with other bothersome symptoms. A new fixed dose combination, containing Silodosin and Solifenacin, has been recently launched for relieving such disorder associated with overactive bladder syndrome. In the current work, three smart, innovative and white spectrophotometric methods have been newly developed and optimized for simultaneous determination of the studied drugs in their binary mixture using water as an eco-friendly solvent. The adopted strategy relied on calculation of one or two factors as numerical constant or spectrum allowing mathematical filtration of desired analyte and full removal of any overlapped components in the mixture. The developed methods are categorized over two spectrophotometric platform windows. Window I deals with absorption spectra in its native forms (zero-order) including a newly developed method termed induced concentration subtraction (ICS) as well as induced dual wavelength (IDW) methods. Whereas window III is concerned with ratio spectra as in induced amplitude modulation (IAM) method. Compared to classical spectrophotometric methods, the proposed ones are superior in overcoming the inherited challenges in zero-order absorption spectrum of Solifenacin, particularly its very low absorptivity and lack of unique absorption maximum. Validity of the methods were thoroughly assured as per ICH guidelines with unified regression over 3.0–50.0 µg/mL in ICS method while IDW and IAM ones possessed linearity ranges of 3.0–50.0 µg/mL of Silodosin and 5.0–60.0 µg/mL of Solifenacin. The work was also extended to verify content uniformity of dosage units in accordance with USP recommendations. Greenness profile of the proposed methods was clearly assessed, in comparison to the reported analysis ones, via state-of-the-art software metrics, namely, green solvent selection tool (GSST), complementary green analytical procedure index (ComplexGAPI) and analytical greenness (AGREE). Finally, the proposed methods were in good adherence to the recently published postulates of white analytical chemistry.

Folic acid capped bimetallic nanoparticle based fluorescence sensor for the nanomolar determination of bilirubin

Folic acid capped Silver-Copper bimetallic nanoparticle (FA-AgCu BNP) based turn-off fluorescence sensor has been developed for the rapid and facile determination of a prominent disease biomarker, Bilirubin. FA-AgCu BNP has been characterised via Fluorescence spectroscopy, EDX, TEM, DLS, Zeta potential, UV–visible spectroscopy, FTIR spectroscopy and XPS techniques. Fluorescence quenching of FA-AgCu BNP has been observed in the presence of bilirubin which is due to the combined effect of static quenching and Inner filter effect. Different analytical parameters were optimised and under these conditions, the sensor showed good selectivity towards bilirubin and attained a wide linear range from 2.00 × 10-5M to 1.00 × 10-7M with a limit of detection of 5.53 × 10-9 M. Practical utility of the proposed sensor has been illustrated in synthetic physiological fluids by spike recovery analysis and the obtained results were validated using classical spectrophotometric method.

Development and Validation of Derivative UV Spectrophotometric method for Simultaneous Determination of Amoxicillin and Clavulanic acid in Tablets (Augmentin 1000mg)

The simultaneous analysis of pharmaceutical mixtures by classical spectrophotometric methods without prior separation is a challenge owing to the strong overlapping of their zero order spectra (low selectivity). Hence, several techniques have been developed for solving this problem, such as derivative spectrophotometry. The aim of this study was to develop a simple, fast, accurate, precise, economical, and eco-friendly derivative spectrophotometric method for the quantitative determination of a binary mixture of amoxicillin (Amox) and clavulanic acid (Clav) without prior separation steps. The developed method is based on the use of first derivative spectra resulting from derivatisation of zero order, with using these parameters (d𝛌=4 and scaling factor=15). The measurements were achieved by using zero-crossing technique (𝛌= 278.5nm for Amox and 𝛌= 228.3nm for Clav), which eliminated the overlapping caused by two drugs and excipients of tablets. The method showed significant linearity in the range (5 45μg/ml with =0.9998) and (1 - 10μg/ml with =0.9986) for Amox and Clav, respectively. The developed technique was validated according to the ICH guidelines. The method was successfully utilized for the simultaneous determination of Amox and Clav in the formulation. The obtained results were statistically compared with the reported method (HPLC) by applying t-test and F-value at 95% confidence level. No significant difference was observed regarding accuracy and precision. Hence,the proposed procedure can be utilized for regular quality control studies as alternative to chromatographic techniques.

INTERACTION OF HAFNIUM(IV) WITH 6,7-DIHYDROXY‑4-CARBOXYL‑2- PHENYLBENZOPYRYLLIUM SALTS IN BINARY SYSTEMS AND IN THE PRESENCE OF CATIONIC SURFACTANTS

In the current study, the peculiarities of the complexation of Hafnium(IV) with 6,7-dihyroxy‑4-carboxyl‑2-phenylbenzopyrylium salts (CDC) in binary systems and in the presence of cationic surfactants (Surf) were studied. The CDC was synthesized by condensation of pyrogallol A with benzoylpyruvic acid in an acetic acid medium in the presence of perchloric acid. To obtain KDC bromide and chloride, the synthesis was carried out in the presence of bromide acid or by sparging of dry hydrogen chloride, respectively. Using classical spectrophotometric methods of molar ratios and Bent-French, it was found that at pH 2.5 in binary system one complex with stoichiometry Hf(IV): CDC1:2 was formed. Molar absorptivity coefficient was calculated for Hf(IV) complex with CDC and it was equal 3,9⸱104. It was shown that in the presence of cetylpyridinium chloride or cetyltrimetrylammonium bromide complexes with a molar ratio of Hf(IV): CDC: Surf = 1:2:2 were formed. It is noted that the complexes were formed within 10–15 minutes, and the absorbance of the solutions remains constant for at least 2 hours. It was established that the nature of the anion, which is part of the reagent, does not significantly affect the characteristics of the analytical form. It is shown that in the presence of cationic surfactants, the optimal pH of complex formation shifts to a more acidic region. In addition, the introduction of cationic surfactants leads to a batachromic shift of the absorption band by 10–15 nm and an increase in the molar absorptivity to 5.8⸱104 and 6.4⸱104 when cetylpyridinium chloride or cetyltrimetrylammonium bromide were used respectively. It is noted that the found analytical forms can be used as a basis for the development of combined spectroscopic methods for determining trace amounts of Hafnium(IV).

SPECTROPHOTOMETRIC DETERMINATION OF STIBIUM (III) WITH 6,7-DIHYDROXY‑4-CARBOXYL‑2- PHENYLBENZOPYRILIUM PERCHLORATE

In the current study, the peculiarities of the complexation of Stibium(III) with 6,7-dihydroxy‑4-carboxyl‑2-phenylbenzopyrylium perchlorate (CDC) in binary systems and in the presence of cationic surfactants (Surf) were studied. Using classical spectrophotometric methods of molar ratios and equilibrium shift, it was found that in two systems two complexes with stoichiometry Sb(III): CDC are formed: 1:2 and 1:3 at pH 2.5 and pH 6.0, respectively. Molar absorptivity coefficients were calculated for Sb(III) complexes with CDC, which are 1.2⋅104 and 1.1⋅104, respectively. It is shown that in the presence of cetylpyridinium chloride or cetyltrimetrylammonium bromide complexes with a molar ratio of Sb(III): CDC: Surf =1:3:3 are formed. In the presence of cationic surfactants there is no shift in the optimal pH of complexation, but there is an increase in the number of coordinated reagent molecules due to the loosening of the hydrate shell of the ion Sb(III) due to hydrophobic hydration of the complex. In addition, the introduction of cationic surfactants leads to a batochromic shift of the absorption band by 10–15 nm and an increase in the molar absorptivity to 2.8⋅104 and 3.4⋅104 when cetylpyridinium chloride or cetyltrimetrylammonium bromide were used respectively. The method of spectrophotometric determination of Stibium(III) was developed using an analytical form based on the ternary complex Sb(III): KDC: Surf = 1:3:3, which was tested during the analysis of samples of polymer materials (polyethylene terephthalate). It is noted that the developed technique is characterized by satisfactory reproducibility and is not inferior in sensitivity to known analogues.

New Voltammetric Sensor Based on LDH and H2O2 for L-Proline Determination in Red and White Wines

Taking inspiration from our recent work in which a new sensor for hydrogen peroxide was proposed, our research group has now developed a simple, fast, and inexpensive voltametric system for determining proline concentration both in standard solutions and in real samples (red and white wines). This system uses a non-enzymatic sensor based on a working electrode of glassy carbon (GC) modified with a layered double hydroxide (LDH) compound, of the type GC-Ag(paste)-LDH-H2O2, with hydrogen peroxide in solution at fixed concentration, in a three electrode cyclic voltammetry setup. Using an increasing concentration of standard solutions of L-proline, the method shows a linearity range, in semilogarithmic coordinates, between 125 μmol L−1 and 3200 μmol L−1 of proline, with a limit of detection (LOD) value of 85.0 μmol L−1 and a limit of quantitation (LOQ) value of 95.0 μmol L−1. The developed method is applied to the determination of proline in several samples of commercial Italian wines. The results are compared with those obtained by applying the classic spectrophotometric method of ninhydrin, obtaining a good correlation of the results.

SPECTROPHOTOMETRIC DETERMINATION OF BISMUTH (III) WITH 6,7-DIHYDROXY‑4-CARBOXYL‑2-PHENYLBENZOPYRILIUM PERCHLORATE

In the current study, the peculiarities of the complexation of Bi(III) with 6,7-dihyroxy‑4-carboxyl‑2-phenylbenzopyrylium perchlorate (CDC) in binary systems and in the presence of cationic surfactants (Surf) were studied. Using classical spectrophotometric methods of molar ratios and equilibrium shift, it was found that in two systems two complexes with stoichiometry Bi(III): CDC are formed: 1:2 and 1:3 at pH 2.0 and pH 4.5, respectively. Molar light absorption coefficients were calculated for Bi(III) complexes with CDC, which are 1.4⸱104 and 1.0⸱104, respectively. It is shown that in the presence of cetylpyridinium chloride or cetyltrimetrylammonium bromide complexes with a molar ratio of Bi(III): CDC: Surf =1:3:3 are formed. In the presence of cationic surfactants there is no shift in the optimal pH of complexation, but there is an increase in the number of coordinated reagent molecules due to the loosening of the hydrate shell of the ion Bi(III) due to hydrophobic hydration of the complex. In addition, the introduction of cationic surfactants leads to a batochromic shift of the absorption band by 10–15 nm and an increase in the molar absorption coefficient to 3.1⸱104 and 4.1⸱104 when using cetylpyridinium chloride or cetyltrimetrylammonium bromide, respectively. Methods of spectrophotometric determination of Bi(III) with the use of analytical forms based on complexes of 1:2 and ternary complex 1:3:3 were developed, which were tested in the analysis of pharmaceuticals, alloys and model solutions. It is noted that the proposed methods are characterized by satisfactory reproducibility and are not inferior in sensitivity to known analogues.

Activity measurement of arylsulfatase and β-glucuronidase in activated sludge: HPLC-based versus classical spectrophotometric method.

Arylsulfatase and β-glucuronidase are two important enzymes in wastewater and surface water, which play important roles on cleavage of sulfate/glucuronide estrogens. In this work, a high-performance liquid chromatography (HPLC)-based new method was firstly established for arylsulfatase/β-glucuronidase with determination of p-nitrophenyl sulfate (pNPS)/p-nitrophenyl-β-D-glucuronide (pNPG). The limits of detections (LODs) of the developed method for pNPS and pNPG were 0.164 and 0.098 μM, respectively. Intraday and interday reproducibility expressed as relative standard deviation (RSD) values of retention times and peak areas was 0.39%-3.68% and 0.23%-4.74%, respectively. The respective recovery efficiencies of this HPLC-based method spiking at three different concentrations for p-nitrophenol (pNP), pNPS, and pNPG in activated sludge were 76.5%-88.1%, 79.2%-93.1%, and 84.2%-96.1%, with RSD below 3.9%. The HPLC-based method was finally applied to estimate the enzyme activity of arylsulfatase/β-glucuronidase in one activated sludge system and along which the classical spectrophotometric method was also evaluated. Compared with the classic spectrophotometric analytical method, the HPLC-based new method could simultaneously measure arylsulfatase/β-glucuronidase one time, which was convenient and time-saving. Moreover, the developed method could effectively avoid possible underestimation that the spectrophotometric method might encounter. PRACTITIONER POINTS: A new HPLC-based method for activity estimation of arylsulfatase and β-glucuronidase was developed. The HPLC-based method can simultaneously estimate enzyme activity of both arylsulfatase and β-glucuronidase. The HPLC-based method can avoid possible underestimation that spectrophotometric method may encounter.

Development and characterization of a gold nanoparticles glassy carbon modified electrode for dithiotreitol (DTT) detection suitable to be applied for determination of atmospheric particulate oxidative potential

A gold nanostructured electrochemical sensor based on modified GC electrode for thiols' detection is described and characterized. This sensor is a suitable device for the measurement of the oxidative potential (OP) of the atmospheric particulate matter (PM), considered a global indicator of adverse health effects of PM, as an alternative to the classic spectrophotometric methods. The operating principle is the determination of the OP, through the measurement of the consumption of DTT content. The DTT-based chemical reactivity is indeed a quantitative acellular probe for assessment of the capacity of the atmospheric PM to catalyze reactive oxygen species generation which contributes to the induction of oxidative stress in living organisms and in turn to the outcome of adverse health effects. To make the sensors, glassy carbon electrodes, traditional (GC) and screen printed (SPE) electrodes, have been electrochemically modified with well-shaped rounded gold nanoparticles (AuNPs) by using a deposition method that allows obtaining a stable and efficient modified surface in a very simple and reproducible modality. The chemical and morphological characterization of the nano-hybrid material has been performed by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy coupled with electron dispersive spectroscopy analysis (SEM/EDS). The electrochemical properties have been evaluated by cyclic voltammetry (CV) and chrono-amperometry (CA) in phosphate buffer at neutral pH as requested in DTT assay for OP measurements. The electroanalytical performances of the sensor in DTT detection are strongly encouraging showing low LODs (0.750 μM and 1.5 μM), high sensitivity (0.0622 μA cm−2 μM−1 and 0.0281 μA cm−2 μM−1), wide linear and dynamic ranges extending over 2-4 orders of magnitude and high selectivity. FIA preliminary results obtained on measuring the DTT rate consumption in six PM aqueous extracts samples showed a good correlation with measurements obtained in parallel on the same set of samples by using the classic spectrophotometric method based on the Ellman's reactive use. These results confirm the high selectivity of the method and its suitability for application to be applied in PM oxidative potential measurements.

ANTIOXIDANT AND ANTIRADICAL ACTIVITY IN VITRO OF EXTRACTS FROM THE LEAVES OF RUBUS CHAMAEMORUS L. (ROSACEAE)

Cloudberry (Rubus chamaemorus L.) is the leader among northern berries in the content of phenolic compounds, which can cause a wide range of biological activity. Currently, there is an increased interest in the study of the antioxidant activity of plant extracts in order to search for promising sources of raw materials for the pharmaceutical and food industries. The article presents the results of a comparative analysis of interpopulation and gender differences in antioxidant and antiradical activities in vitro of cloudberry leaf extracts growing on the territory of the Republic of Belarus. Classical spectrophotometric methods were used for determination: phosphomolibdenic method, Fe + 2-chelating activity, NO-inhibiting activity, inhibition of hydroxyl radicals (OH), method of superoxide radical inhibition in an alkaline solution of dimethylsulfoxide, DPPH, ABTS. Differences in the content of phenolic compounds and flavonoids in the alcoholic extracts of leaf blades of Rubus chamaemorus L. It was found that the population of the Bolshoi Mokh preserve possesses the highest inhibition rates of hydroxyl radicals and superoxide radicals. The maximum iron-chelating activity was exhibited by the extracts of the male plant of the Bolshoy Moh preserve. The least inhibitory activity of Rubus chamaemorus L. leaf extracts was shown to the nitrogen-oxide radical. The established values of antioxidant and antiradical activities, as well as the content of phenolic compounds and flavonoids of the leaf blades of Rubus chamaemorus L. may be important for the development of measures to preserve the species and specific populations on the southern border of the habitat.

Two Novel Methods for the Determination of Benzalkonium Chloride in Bandages by Resonance Light Scattering Technology

Abstract In this study, two novel resonance light scattering (RLS) methods were developed for the determination of benzalkonium chloride. These methods were based on the formation of inorganic anionic-surfactant aggregates in a Clark-Lubs medium, which increases the resonance light scattering intensity of the reaction system and were also predominantly divided into sodium tungstate-benzalkonium chloride (method A) or phosphomolybdate-benzalkonium chloride (method B). The detection is performed both at 285 nm. Under the established conditions, the limits of quantification ranged from 0.10 mg L–1 to 1.00 mg L–1 with the R values of 0.9994 and from 0.20 mg · L–1 to 3.20 mg · L–1 with the R values of 0.9991, with good precision and accuracy both for method A and method B. The limits of detection were 0.029 mg · L–1 for method A and 0.013 mg · L–1 for method B. These two methods were successfully applied for the assay of benzalkonium chloride for the first time. All validation parameters were in agreement with the International Conference on Harmonization of Requirements for Registration Pharmaceuticals for Human Use (ICH) guidelines. Compared to the classical spectrophotometric method, these two methods take advantages of rapidity, high efficiency and good selectivity.

Glucose Biosensor Based on Disposable Activated Carbon Electrodes Modified with Platinum Nanoparticles Electrodeposited on Poly(Azure A).

Herein, a novel electrochemical glucose biosensor based on glucose oxidase (GOx) immobilized on a surface containing platinum nanoparticles (PtNPs) electrodeposited on poly(Azure A) (PAA) previously electropolymerized on activated screen-printed carbon electrodes (GOx-PtNPs-PAA-aSPCEs) is reported. The resulting electrochemical biosensor was validated towards glucose oxidation in real samples and further electrochemical measurement associated with the generated H2O2. The electrochemical biosensor showed an excellent sensitivity (42.7 μA mM−1 cm−2), limit of detection (7.6 μM), linear range (20 μM–2.3 mM), and good selectivity towards glucose determination. Furthermore, and most importantly, the detection of glucose was performed at a low potential (0.2 V vs. Ag). The high performance of the electrochemical biosensor was explained through surface exploration using field emission SEM, XPS, and impedance measurements. The electrochemical biosensor was successfully applied to glucose quantification in several real samples (commercial juices and a plant cell culture medium), exhibiting a high accuracy when compared with a classical spectrophotometric method. This electrochemical biosensor can be easily prepared and opens up a good alternative in the development of new sensitive glucose sensors.

Fluorescent optrode for proteins based on a diketopyrrolopyrrole derivative: Practical application to total protein determination in urine

A fluorescence sensor based on a diketopyrrolopyrrole (DPP) derivative for protein detection was designed and tested in urine samples. The DPP derivative emits visible light as a solid, making this molecule particularly appealing as a recognition molecule for a sensing optical fibre. In the presence of proteins, the sensor displayed a fluorescence enhancement. The sensor linear dynamic range for protein ranges from 10 mg L−1 to 100 mg L−1. Detection limit (LOD) of this fluorescent optrode was better than the one of the classical spectrophotometric Biuret method and similar to the LOD of the spectrophotometric Ponceau-S/TCA method. The economy of reagents and time is a clear advantage of the analytical method based on the optrode we are now proposing, regarding the Ponceau-S/TCA, thanks to the reversibility of recognition layer, and to the needless of treating the standards with trichloroacetic acid, and consequently of centrifuging them. Besides, the most common interferences in protein determination by classical spectrophotometric methods, like sodium dodecyl sulfate, acetone, and glucose, do not affect the optrode response, neither does fluoride ion.The new fluorescent optrode was tested in the determination of total proteins in urine from healthy individuals (low concentrations). Results were not statistically different from the ones obtained with the Ponceau-S/TCA spectrophotometric method.

Simultaneous Determination and Quantification of Triterpene Saponins from Camellia sinensis Seeds Using UPLC-PDA-QTOF-MS/MS.

Saponins in the Camellia sinensis seeds have a broad spectrum of biological properties and application potentials. However, up to now, no chromatographic methods have been developed to provide full fingerprinting and quality assurance for these saponins. This research aimed to develop a novel method to tentatively identify and quantify saponins in C. sinensis seeds by ultra-high-performance liquid chromatography coupled with photo-diode array detector and quadrupole time-of-flight mass spectrometry (UPLC-PDA-QTOF-MS/MS), and compare it with the classic vanillin-sulfuric acid assay. Fifty-one triterpene saponins, including six potentially new compounds, were simultaneously detected by UPLC-PDA-MS/MS, and their chemical structures were speculated according to the retention behavior and fragmentation pattern. The total saponin content in the crude extract and the purified saponin fraction of C. sinensis seeds were quantified to be 19.57 ± 0.05% (wt %) and 41.68 ± 0.09% (wt %) respectively by UPLC-PDA at 210 nm, while the corresponding values were determined to be 43.11 ± 3.17% (wt %) and 56.60 ± 5.79% (wt %) respectively by the vanillin-sulfuric acid assay. The developed UPLC-PDA -MS/MS method could determine specified saponins, and is more reliable for quantifying the C. sinensis seed saponins than the classic spectrophotometric method. It is of great significance for the future investigations and applications of these saponins.

Cocoa powder and catechins as natural mediators to modify carbon-black based screen-printed electrodes. Application to free and total glutathione detection in blood

In this work, for the first time, the direct usability of natural products, catechins (CT) and cocoa powder (CO), as electrochemical mediators able to modify a carbon black modified screen-printed electrode (SPE-CB) is proved, and, as proof of applicability, free (GSH) and total glutathione (GSH + GSSG) in blood samples is successfully determined. Noteworthy, the cocoa powder (naturally rich in catechins), dissolved in DMSO, was able to give rise to a useful highly redox-active catechol-quinone surface-confined system onto a carbon black nanoparticles modified screen-printed electrode (SPE-CB-CO – Cocoatrode), giving rise to a similar behaviour obtained with pure catechins (SPE-CB-CT). The electrodeposition process has been carefully studied, the resulting immobilized natural mediator (obtained using both CT and CO) features investigated, and the performance of the resulting sensors (SPE-CB-CT and Cocoatrode) tested and compared. Both modified electrodes (SPE-CB-CT and Cocoatrode) have a good inter-electrodes precision (RSD ip,a ≤ 4.2%, n = 3) and intra-electrodes repeatability (RSD ip,a ≤ 3.9%, n = 20), indicating a robust and stable ‘fabrication’ strategy. Finally, SPE-CB-CT and Cocoatrode have been employed for the detection of free (GSH) and total (GSH+GSSG) glutathione in blood samples, using differential pulse voltammetry decrease in the mediator's reduction peak (Δi %), as analytical signal. Analytical curves (R2 ≥ 0.998), for the GSH detection, have been determined both with SPE-CB-CT and Cocoatrode in the 2.5 × 10−8-6.0 × 10−5 M and 5.0 × 10−8-1.0 × 10−4 M concentration ranges, respectively. Limits of detections (LODs) were ≤2.6 × 10−8 M. GSH (free and total) determined in blood samples, by the proposed CT and CO sensors, showed a good intra-electrode repeatability (RSD ip,a ≤ 9.0%, n = 3), with good recoveries (from 88.3% to 117.7%). The values obtained were in agreement with a classical spectrophotometric method (GSH and GSSG concentration relative error between −4.7 and +9.8%). The SPE-CB-CT and the Cocoatrode platforms demonstrated high potentiality in sensing and biosensing scenario, opening new gates to the natural/food products employment as unconventional, eco-friendly and economically affordable analytical active tools.

Antioxidant activity of Vitis vinifera, Punica granatum, Citrus aurantium and Opuntia ficus indica fruits cultivated in Algeria

Four edible fruits from Vitis vinifera, Punica granatum, Citrus aurantium and Opuntia ficus indica from Algeria were analyzed in order to determine the total polyphenol, total flavonoid and flavonol contents using classical spectrophotometric methods. The antioxidant activity was established by three different single-electron-transfer-based assays (ABTS radical cation, FRAP, and DPPH assays) and one hydrogen-atom-transfer based assay (ORAC). Among the four fruits tested, the Vitis vinifera hydroalcoholic extract showed the highest antioxidant capacity with all methods. The results indicated that the antioxidant activity and the total phenolic content of the selected plants are significantly different (p < 0.001).

Fast and Accurate Electrochemical Measurement of Total Antioxidant Capacity as an Alternative to Spectrophotometrical Methods

Total Antioxidant Capacity or TAC is an indicator of the sample ability to scavenge free radicals despite its complex composition. It has been measured in biological fluids as an inverse biomarker of oxidative stress, which has been related to disease. Classical spectrophotometric methods present some limitations including sample pretreatment required leading to long assay procedures, native pH alteration, low stability of some reagents, high detection limits, low sensitivity and sample’s colour interference.

Metal Oxide Nanoparticle Based Electrochemical Sensor for Total Antioxidant Capacity (TAC) Detection in Wine Samples.

A single-use electrochemical screen-printed electrode is reported based on biomimetic properties of nanoceria particles (CeNPs). The developed tool showed an easy approach compared to the classical spectrophotometric methods reported in literature in terms of ease of use, cost, portability, and unnecessary secondary reagents. The sensor allowed the detection of the total antioxidant capacity (TAC) in wine samples. The sensor has been optimized and characterized electrochemically and then tested with antioxidant compounds occurred in wine samples. The electrochemical CeNPs modified sensor has been used for detection of TAC in white and red commercial wines and the data compared to the 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid (ABTS)-based spectrophotometric method. Finally, the obtained results have demonstrated that the proposed sensor was suitable for the simple and quick evaluation of TAC in beverage samples.

THE PECULIARITIES OF THE COMPLEXATION OF Co(II) WITH 4-SULFO-2 (4'-SULFONAFTALIN-1'-AZO)-NAPHTHOL-1 IN SOLUTIONS

In this paper, the features of the complexation of the “Cobalt(II) -carmoazine-H2O2” system were studied spectrophotometrically. It is shown that the complexation of carmoazine (CAN) with Co(II) is possible only after its oxidation in the presence of hydrogen peroxide. In contrast to the previously investigated ions of variable valency metals that interact with carmoazine according to the mechanism of mutual oxidationreduction, in this case, carmoazine acts as a typical organic ligand. The optimal conditions of interaction in the investigated chemical system (pH 8, 10 vol% H2O2) were established. The complex composition (Co(III):KAN = 1:3) was determined by classical spectrophotometric methods (molar ratios and equilibrium shift). Using the Komar method molar absorbtivity of the complex was calculated (e600 = 5300). The complex stability constant which is 2.4 ∙ 109, was calculated. The presence of Co(III) ions in the newly formed as a result of the oxidation-reduction reaction to the chemical system was proved by using the intake of “interception” of trivalent cobalt ions by the competing ligand – EDTA. The charge (-6) of the product of interaction in the system “Cobalt(II) -carmoazine-H2O2” was determined by the extraction spectrophotometric method. Given the stoichiometry of the complex and the presence in the molecule of carmoazine of two negatively charged outer-sphere sulfo groups, as well as the positive charge of cation of cetylpyridinium (CP+Сl-), the composition of the ion pair extracted with chloroform [Co(III) · 3CAN2- · 6CP+] was determined. An assumption was made about the mechanism of interaction of Co (II) with carmoazine, which is preceded by the oxidation stage of Co(II) in Co(III) to form the transition peroxide complex and its subsequent complexation with carmoazine by the acid-base mechanism.