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Cilj ove doktorske disertacije je određivanje hemijskog sastava ekstrakata komercijalno prerađenog drveta različitog geografskog i biljnog porekla, koje se koristi za izradu buradi za odležavanje rakija u Srbiji. Analizirani su uzorci hrasta lužnjaka i kitnjaka, cera, belog duda, bagrema, džanarike i divlje trešnje. Analizom mikroskopskih preparata uzoraka drveta izvršena je taksonomska identifikacija ispitivanih vrsta. Antioksidativni potencijal i sadržaj ukupnih polifenola vodeno-etanolnih ekstrakata drveta su određeni spektrofotometrijski. Polifenolni profili ekstrakata ispitivani su primenom tankoslojne hromatografije i tečne hromatografije spregnute sa detektorom sa nizom dioda i masenim detektorom. Spektrofluorimetrijski su dobijeni podaci o prisutnim fluoroforama, dok je CIELab metodom određena boja ekstrakata. Antimikrobna aktivnost je ispitana uz pomoć modifikovane difuzione metode u bunarićima i mikrodilucione metode. Gasna hromatografija spregnuta sa masenom spektrometrijom upotrebljena je za identifikaciju i kvantifikaciju isparljivih jedinjenja. Induktivno spregnuta plazma sa optičkom emisionom spektroskopijom korišćena je za određivanje elementalnog sastava. U drugom delu istraživanja izvršeno je simuliranje odležavanja rakija tokom različitih vremenskih intervala korišćenjem različitih ekstrakcionih sredstava (dve vrste rakije i model-rastvor etanola). Ciklična voltametrija i diferencijalno pulsna voltametrija su primenjene za ispitivanje elektrohemijskog ponašanja i antioksidativnog potencijala etanolnih ekstrakata. Rezultati su pokazali da ispitivane vrste drveta obiluju polifenolima, te da postoji mogućnost upotrebe drvnog otpada iz procesa proizvodnje buradi za odležavanje alkoholnih pića. Pored toga, proširena su saznanja o nedovoljno ispitivanim vrstama (džanarika i cer) i pokazan je potencijal analitičkih tehnika koje do sada nisu primenjivane za analizu uzoraka drveta i njihovih ekstrakata (spektrofluorimetrija, ciklična voltametrija i diferen, The aim of this doctoral dissertation is to determine the chemical composition of extracts made from commercial wood samples of different geographical and plant origin, which is used for making barrels for ageing of fruit brandies in Serbia. The following samples were analysed: pedunculate oak, sessile oak, Turkey oak, white mulberry, black locust, Myrobalan plum and wild cherry. Taxonomic identification of the examined plant species was performed by analysis of microscope slides of wood samples. Spectrophotometry was used for determining the radical scavenging activity and the content of total polyphenols of the aqueous-ethanolic wood extracts. Phenolic profiles of the extracts were obtained by thin-layer chromatography and high-performance liquid chromatography coupled to diode array detector and mass spectrometry. Spectrofluorimetry was used for obtaining data about the fluorophores present, while CIELab method was used for measuring the colour of the extracts. Antimicrobial activity was investigated by modified well-diffusion method and microdilution method. Gas chromatography coupled to mass spectrometry was used for identifying and quantifying volatile compounds. Elemental composition was determined by inductively coupled plasma with optical emission spectroscopy. In the second part of the study, simulation of brandy ageing during different time intervals was performed by using different extraction agents (two fruit brandies and a model-ethanol solution). Cyclic voltammetry and differential pulse voltammetry were used for examining electrochemical behaviour and antioxidant capacity of the ethanolic extracts. The results have shown that the investigated wood samples are rich in polyphenols, therefore there is a potential of reusing wood waste from cooperage. In addition, the knowledge is expanded for the insufficiently tested species (Myrobalan plum and Turkey oak) while the potential for using analytical techniques not used before for the analysis of wood samp

Ova disertacija predstavlja kompleksnu analizu kvaliteta vazduha u školskim sredinama i doprinosi boljim saznanjima o nivoima zagađujućih materija prisutnih u obliku čestica i gasova u vazduhu unutrašnjeg prostora škola i njihovom okruženju. U ovoj disertaciji merene su prioritetne zagađujuće materije vazduha za unutrašnji prostor: VOC, NO2, O3, PM2,5, PM10, TSP, kao i PAH-ova u svim frakcijama čestica i gasnoj fazi. Uzorkovanje je vršeno u ukupnom trajanju od tri meseca, sukcesivno u šest osnovnih škola i dva vrtica u Srbiji, koji se nalaze u različitom okruženju. VOC-ovi, NO2 i O3 bili su uzorkovani pomoću pasivnih uzorkivača, dok su frakcije čestica (PM2,5, PM10, TSP) i gasna faza PAH-ova uzorkovani aktivno, pomoću pumpi male zapremine. Nađeno je da su nivoi VOC-ova u unutrašnjem prostoru škola bili daleko viši nego u spoljašnjoj sredini. Rezultati PCA analize ukazali su da ozonoliza i fotohemijske reakcije, emisije iz građevinskih materijala i organski rastvarači, emisije iz sredstava za čišćenje i spoljašnji izvori emisije značajno utiču na nivoe VOC-ova u unutrašnjem prostoru škola. Veće koncentracije čestica u unutrašnjem prostoru i spoljašnjoj sredini zabeležene su tokom grejnog perioda u svim školama, pa je zaključeno da uticaj grejanja tokom zimskih meseci, kao i položaj škole ima bitan uticaj na nivoe PM u učionicama. Takođe, rezultati su pokazali da su koncentracije čestica u unutrašnjem prostoru više nego u spoljašnjoj sredini. Zapaženi su viši nivoi PM2,5 u učionicama tokom školskih sati u poređenju sa nivoima kada su učionice bile prazne. Pokazano je da infiltracija spoljašnjih čestica i njihova naknadna resuspenzija može dovesti do povišenih nivoa čestica u unutrašnjem prostoru škola, a samim tim i do povećanih nivoa PAH-ova. Ispitivanjem raspodele PAH-ova između gasne i čestične faza uočeno je da su najdominantniji PAH-ovi u gasnoj fazi bili Nap, Phe i Flu, dok su najdominantniji u čestičnoj fazi bili BgP, Ind i BbF. Primećeno je da su PAH-ovi sa 5, This dissertation presents a complex analysis of air quality in school environments and contributes to better knowledge about the pollutants levels present in the form of particles and gases in indoor and outdoor air. In this dissertation, priority indoor air pollutants were measured: VOC, NO2, O3, PM2.5, PM10, TSP, as well as PAHs in all particle fractions and PAHs in gas phase. Sampling was carried out over a period of three months, successively in six elementary schools and two kindergartens in Serbia, which are in different environments. VOCs, NO2 and O3 were sampled using passive samplers, while particulate fractions (PM2.5, PM10, TSP) and gas phase PAHs were sampled using low volume pumps. It was found that the levels of VOCs in the indoor space of the schools were much higher than in the outdoor environment. VOC levels in schools were found to be higher indoors than outdoors. The results of the PCA analysis indicated that ozonolysis and photochemical reactions, emissions from building materials and organic solvents, emissions from cleaning agents and outdoor emission sources significantly affect the levels of VOCs in the indoor environment of schools. Higher concentrations of particles in the indoor and outdoor environment were recorded during the heating season in all schools, so it was concluded that the influence of heating during the winter months, as well as the location of the school, have a significant impact on PM levels in classrooms. The results also showed that the concentrations of particles were higher indoor than outdoor. Higher levels of PM2.5 were observed in the classrooms during school hours compared to levels when the classrooms were empty. It has been shown that the infiltration of outdoor particles and their resuspension can lead to elevated levels of indoor particles, and therefore to increased levels of PAHs. By examining the distribution of PAHs between the gas and the particle phases, it was observed that the most dominant PAHs in the

Cilj ove disertacije je primena MFC sistema kao obnovljivog izvora „zelene“ energije za tretman otpadnih voda. U tu svrhu je izvršena optimizacija MFC radi dobijanja struje odgovarajućeg intenziteta, koja se može iskoristiti za razgradnju reaktivnih organskih boja, glavnih zagađujućih supstanci otpadnih voda. Prvi deo istraživanja obuhvata fizičko-hemijsku i mikrobiološku karakterizaciju rečnog sedimenta koji je dalje korišćen za konstrukciju MFC sistema. Formirane su četiri MFC ćelije: sa sterilnim, sa originalnim, sa biostimulisanim i sa biostimulisanim/biaugmentisanim rečnim sedimentom. Merenja napona na formiranim ćelijama su pokazala da MFC sistem sa biostimulisanim sedimentom daje najbolje performanse. Fokus u drugom delu eksperimenata je bio izolovanje i karakterizacija mikroorganizama koji su dominantno zastupljeni u sedimentu, a ujedno su i zaslužni za procese oksidacije u anodnom delu koji omogućavaju generisanje struje preko MFC. Izvršena je metagenomska analiza u uzorku rečnog sedimenta i u biostimulisanom rečnom sedimentu, kako bi se uporedio profil zastupljenih zajednica mikroorganizama. Studija degradacije i dekolorizacije Reactive Black 5 (RB5) azo boje izvedena je pomoću elektrohemijski unapređenog oksidacionog procesa i opisana je u trećem segmentu disertacije. Elektro-Fentonov proces je uspostavljen upotrebom radne elektrode od 15% Fe i dodatkom H2O2 u rastvor RB5 boje, dok je set od tri paralelno vezane MFC, sa biostimulisanim sedimentom, služio kao izvor struje. Optimizacija procesa elektrohemijskog tretmana RB5 je sprovedena na koncentraciji boje od 25 mg/L. Efikasnost degradacija RB5 boje je potvrđena upotrebom analitičkih metoda UV/VIS, FTIR i HPLC-MS. Testovi za procenu ekotoksičnosti, izvedeni pomoću Aliivibrio fischeri, pokazuju da su degradacioni proizvodi nastali u ovom eksperimentu manje toksični od polazne boje, The goal of this dissertation is application of the MFC system as a renewable „green“ energy source in wasterwater treatment. For this purpose MFC was optimized in order to obtain a suitable amount of electricity that can be used to decompose reactive organic dyes, the primary pollutants of wastewaters.The first part of the research includes physico-chemical and microbiological analysis of the river sediment, which was further used to construct the MFC system. Four MFC cells were formed containing: sterile, original, stimulated and biostimulated/bioaugmented river sediment. Voltage measurements on the established cells showed that the MFC with biostimulated sediment exibited the best performance. The focus of the second part of the study was the isolation and characterization of microorganisms that are dominantly represented in the sediment, which enable the generation of current through the MFC. Metagenomic analysis was used to compare the profiles of microbial populations in a composite of river sediment and biostimulated river sediment. The study of degradation and decolorization of Reactive Black 5 (RB5) azo dye investigated using an electrochemically improved oxidation process is described in the last part of the dissertation. The Electro-Fenton process was established using a working electrode of 15% Fe and the addition of H2O2 to the RB5 dye solution, while a set of three MFCs connected in parallel, with biostimulated sediment, served as the current source. Optimization of the RB5 electrochemical treatment process was carried out at a dye concentration of 25 mg/L. The efficiency of degradation of RB5 dye was confirmed using analytical methods UV/VIS, FTIR and HPLC-MS. Ecotoxicity assessment tests, performed using Aliivibrio fischeri, show that the degradation products formed in this experiment are less toxic than the starting dye.

Ova disertacija predstavlja kompleksnu analizu kvaliteta vazduha u školskim sredinama idoprinosi boljim saznanjima o nivoima zagađujućih materija prisutnih u obliku čestica i gasovau vazduhu unutrašnjeg prostora škola i njihovom okruženju. U ovoj disertaciji merene suprioritetne zagađujuće materije vazduha za unutrašnji prostor: VOC, NO2, O3, PM2,5, PM10,TSP, kao i PAH-ova u svim frakcijama čestica i gasnoj fazi. Uzorkovanje je vršeno u ukupnomtrajanju od tri meseca, sukcesivno u šest osnovnih škola i dva vrtica u Srbiji, koji se nalaze urazličitom okruženju. VOC-ovi, NO2 i O3 bili su uzorkovani pomoću pasivnih uzorkivača, doksu frakcije čestica (PM2,5, PM10, TSP) i gasna faza PAH-ova uzorkovani aktivno, pomoćupumpi male zapremine. Nađeno je da su nivoi VOC-ova u unutrašnjem prostoru škola bilidaleko viši nego u spoljašnjoj sredini. Rezultati PCA analize ukazali su da ozonoliza ifotohemijske reakcije, emisije iz građevinskih materijala i organski rastvarači, emisije izsredstava za čišćenje i spoljašnji izvori emisije značajno utiču na nivoe VOC-ova uunutrašnjem prostoru škola. Veće koncentracije čestica u unutrašnjem prostoru i spoljašnjojsredini zabeležene su tokom grejnog perioda u svim školama, pa je zaključeno da uticajgrejanja tokom zimskih meseci, kao i položaj škole ima bitan uticaj na nivoe PM u učionicama.Takođe, rezultati su pokazali da su koncentracije čestica u unutrašnjem prostoru više nego uspoljašnjoj sredini. Zapaženi su viši nivoi PM2,5 u učionicama tokom školskih sati u poređenjusa nivoima kada su učionice bile prazne. Pokazano je da infiltracija spoljašnjih čestica i njihovanaknadna resuspenzija može dovesti do povišenih nivoa čestica u unutrašnjem prostoru škola,a samim tim i do povećanih nivoa PAH-ova. Ispitivanjem raspodele PAH-ova između gasne ičestične faza uočeno je da su najdominantniji PAH-ovi u gasnoj fazi bili Nap, Phe i Flu, doksu najdominantniji u čestičnoj fazi bili BgP, Ind i BbF. Primećeno je da su PAH-ovi sa 5 i 6benzenovih prsteno, This dissertation presents a complex analysis of air quality in school environments andcontributes to better knowledge about the pollutants levels present in the form of particles andgases in indoor and outdoor air. In this dissertation, priority indoor air pollutants weremeasured: VOC, NO2, O3, PM2.5, PM10, TSP, as well as PAHs in all particle fractions andPAHs in gas phase. Sampling was carried out over a period of three months, successively insix elementary schools and two kindergartens in Serbia, which are in different environments.VOCs, NO2 and O3 were sampled using passive samplers, while particulate fractions (PM2.5,PM10, TSP) and gas phase PAHs were sampled using low volume pumps. It was found that thelevels of VOCs in the indoor space of the schools were much higher than in the outdoorenvironment. VOC levels in schools were found to be higher indoors than outdoors. The resultsof the PCA analysis indicated that ozonolysis and photochemical reactions, emissions frombuilding materials and organic solvents, emissions from cleaning agents and outdoor emissionsources significantly affect the levels of VOCs in the indoor environment of schools. Higherconcentrations of particles in the indoor and outdoor environment were recorded during theheating season in all schools, so it was concluded that the influence of heating during the wintermonths, as well as the location of the school, have a significant impact on PM levels inclassrooms. The results also showed that the concentrations of particles were higher indoorthan outdoor. Higher levels of PM2.5 were observed in the classrooms during school hourscompared to levels when the classrooms were empty. It has been shown that the infiltration ofoutdoor particles and their resuspension can lead to elevated levels of indoor particles, andtherefore to increased levels of PAHs. By examining the distribution of PAHs between the gasand the particle phases, it was observed that the most dominant PAHs in the gas phase wereNap, P

The modern lifestyle has increased our utilization of pollutants such as heavy metals, aromatic compounds, and contaminants that are of rising concern, involving pharmaceutical and personal products and other materials that may have an important environmental impact. In particular, the ultimate results of the intense use of highly stable materials, such as heavy metals and chemical restudies, are that they turn into waste materials, which, when discharged, accumulate in environmental water bodies. In this context, the present review presents the application of metal–organic frameworks (MOFs) in electrochemiluminescent (ECL) sensing for water pollutant detection. MOF composites applied as innovative luminophore or luminophore carriers, materials for electrode modification, and the enhancement of co-reaction in ECL sensors have enabled the sensitive monitoring of some of the most common contaminants of emerging concern such as heavy metals, volatile organic compounds, pharmaceuticals, industrial chemicals, and cyanotoxins. Moreover, we provide future trends and prospects associated with ECL MOF composites for environmental sensing.

Stable, water-soluble titanium complexed with mandelic acid was used as a precursor for titanium phosphorus double oxide obtained in hydrothermal conditions in the presence of phosphoric acid. Surprisingly, hydrolysis of organic complexes provided a microstructured sphere with narrow size distribution, low aggregation and a small fraction of morphological irregularities. Obtained microspheres had a complex structure comprised of flakes, whose size could be manipulated with temperature conditions. Samples were found to be electrochemically active against sulcotrione, a well-recognized herbicide. Electrochemical sensors based on the synthesized microspheres were successfully adapted for natural water reservoir analysis and exhibited low levels of detection of 0.61 µM, limit of quantification of 1.86 µM, wide dynamic linear range from 2 to 200 µM, good selectivity, excellent reproducibility and in-time stability.

In this paper, electrochemical degradation of Reactive Black 5 (RB5) textile azo dye was examined in regard to different synthesis procedures for making PbO2–graphitic carbon nitride (g-C3N4) electrode. The reaction of Pb(OH)−3 with ClO− in the presence of different surfactants, i.e., cetyltrimethylammonium bromide (CTAB) and tetrabutylammonium phosphate (TBAP), under conventional conditions, resulted in the formation of PbO2 with varying morphology. The obtained materials were combined with g-C3N4 for the preparation of the final composite materials, which were then characterized morphologically and electrochemically. After optimizing the degradation method, it was shown that an anode comprising a steel electrode coated with the composite of PbO2 synthesized using CTAB as template and g-C3N4, and using 0.15 M Na2SO4 as the supporting electrolyte, gave the best performance for RB5 dye removal from a 35 mg/L solution. The treatment duration was 60 min, applying a current of 0.17 A (electrode surface 4 cm2, current density of 42.5 mA/cm2), while the initial pH of the testing solution was 2. The reusability and longevity of the electrode surface (which showed no significant change in activity throughout the study) may suggest that this approach is a promising candidate for wastewater treatment and pollutant removal.

Lowlands of Central Serbia are mostly covered by alluvial soils, while the natural vegetation types are various alluvial forests differentiated by the distance from the river bad (dynamics of soil water potential regimes) and gradients of soil structure, nutrient availability and soil pH (Marjanovic et al 2020). These forests have been heavily exploited for timber throughout the human history, but what has remained still represent significant hotspots of above and belowground biodiversity. The rare specificity of these ecosystems is the high diversity of truffles, fungi producing belowground fruiting bodies, among which the most prised white Piedmont truffle holds a special attention (Bragato and Marjanovic, 2016). In order to describe these special habitats of Balkan Peninsula, we have conducted various experiments, mostly concentrated on soils that support the fructification of this ecologically and economically important species. In this contribution we will summarize results on soil structure, soil water content dynamics, nutrient availability, seasonality of soil processes as well as seasonality of root associated mycobiomes of selected alluvial forests. We focus on connecting the fructification of white truffle to different soil factors (Marjanovic et al 2015), as well as on defining the differentiation factors that have been shaping root associated mycobiomes (Marjanovic et al 2020). The contribution was set to uncover as many soil traits as possible to reveal the answer to the question of what are the ideal conditions of soil/vegetation /climate combination that is suitable for such specific fungal communities.

Pesticides have a significant role in the world food chain in the setting of rising agricultural output demand and rising climate change impacts on agricultural productivity. Pesticide contamination across the world is not just a pressing issue; it also has the potential to get worse, for instance, because of movements in global production to nations with laxer environmental regulations [1]. In this work, we have designed a new electrochemical sensor for detecting bentazone (BZT) by using NP-Y2O3/g-C3N4 modified carbon paste electrode (CP). For the first time, the Pechini method was employed to synthesize the Y2O3 nanocomposite. The nanomaterial was characterized by Xray powder diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). In order to create an analytical technique for identifying and measuring BZT, the electrocatalytic characteristics of the suggested Y2O3/g-C3N4 modified CP electrode were examined. Using the CV and DPV approaches, the electrochemical behavior of BZT at the Y2O3/gC3N4 sensor was investigated. The proposed electrochemical sensor exhibited excellent electrochemical response toward BZT with a wide linear range of 1 to 100 µM, with a detection limit of 0.68 µM. The effect of possible interfering agents is negligible, confirming the good selectivity of the method. The sensor also displayed excellent sensitivity, reproducibility, and stability. Additionally, the Y2O3/g-C3N4 sensor was utilized for the detection of BZT in water and soil samples, and also in red and green pepper samples, and it exhibited good recovery results.

There are ten million people in the world who have Parkinson’s disease. The most potent medicine for Parkinson’s disease is levodopa (L-DOPA). However, long-term consumption of L-DOPA leads to the appearance of side effects, as a result of which the control and monitoring of its concentrations are of great importance. In this work, we have designed a new electrochemical sensor for detecting L-DOPA using a carbon paste electrode (CPE) modified with Eu2O3@Cr2O3 composite nanoparticles. Rare earth elements, including Eu, are increasingly used to design new electrode nanocomposites with enhanced electrocatalytic properties. Europium has been considered a significant lanthanide element with greater redox reaction behavior. We conducted a hydrothermal synthesis of Eu2O3@Cr2O3 and, for the first time, the acquired nanoparticles were used to modify CPE. The proposed Eu2O3@Cr2O3/CPE electrode was investigated in terms of its electrocatalytic properties and then used to develop an analytical method for detecting and quantifying L-DOPA. The proposed sensor offers a wide linear range (1–100 µM), high sensitivity (1.38 µA µM−1 cm−2 ) and a low detection limit (0.72 µM). The practical application of the proposed sensor was investigated by analyzing commercially available pharmaceutical tablets of L-DOPA. The corresponding results indicate the excellent potential of the Eu2O3@Cr2O3/CPE sensor for application in real-time L-DOPA detection

In this paper, electrochemical degradation of Reactive Black 5 (RB5) textile azo dye was examined in regard to different synthesis procedures for making PbO2–graphitic carbon nitride (g-C3N4) electrode. The reaction of with ClO− in the presence of different surfactants, i.e., cetyltrimethylammonium bromide (CTAB) and tetrabutylammonium phosphate (TBAP), under conventional conditions, resulted in the formation of PbO2 with varying morphology. The obtained materials were combined with g-C3N4 for the preparation of the final composite materials, which were then characterized morphologically and electrochemically. After optimizing the degradation method, it was shown that an anode comprising a steel electrode coated with the composite of PbO2 synthesized using CTAB as template and g-C3N4, and using 0.15 M Na2SO4 as the supporting electrolyte, gave the best performance for RB5 dye removal from a 35 mg/L solution. The treatment duration was 60 min, applying a current of 0.17 A (electrode surface 4 cm2, current density of 42.5 mA/cm2), while the initial pH of the testing solution was 2. The reusability and longevity of the electrode surface (which showed no significant change in activity throughout the study) may suggest that this approach is a promising candidate for wastewater treatment and pollutant removal.

Herein, a screen–printed diamond electrode (SPDE) coupled with a “point-of-care” platform (30 µL-drop concepts, single-drop-detection approach) was successfully applied for the electrochemical determination of pterostilbene (PTS). Cyclic voltammetry identified irreversible oxidation of PTS, where oxidation peak was shown to be strongly dependent on the pH of the working environmental. Although the proposition of the detailed electrochemical oxidation mechanism of PTS goes out of the scope of the present research, we have determined the most probable reactive site of our analyte, by utilizing DFT-based reactivity descriptors (Fukui functions). For electrochemical quantification of PTS, oxidation peak at 0.32 V (vs. Ag/AgCl) was followed in presence of 0.5 mol L−1 of Briton–Robinson buffer solution (pH = 9). Coupled with the optimized parameters of differential pulse voltammetry (DPV), SPDE detected PTS in two linear ranges (first range was from 0.011 to 0.912 µmol L−1; second range was from 0.912 to 4.420 µmol L−1), providing the LOD and LOQ on a nanomolar level (3.1 nmol L−1 and 10.0 nmol L−1, respectively). The selectivity of the optimized DPV method was found to be excellent, with the current changes of less than 7%, in the presence of ten times higher concentrations of the certain interferences. The practical applicability of the SPDE and single-drop-detection approach in dietary supplements (with a declared PTS content of 50 mg/tablet), with the recovery values ranging from 95 to 102%, shows that the developed method has high potential for precise and accurate PTS detection, as well as exceptional miniaturization possibilities of relevant equipment for on-site sensing.

There are ten million people in the world who have Parkinson’s disease. The most potent medicine for Parkinson’s disease is levodopa (L-DOPA). However, long-term consumption of L-DOPA leads to the appearance of side effects, as a result of which the control and monitoring of its concentrations are of great importance. In this work, we have designed a new electrochemical sensor for detecting L-DOPA using a carbon paste electrode (CPE) modified with Eu2O3@Cr2O3 composite nanoparticles. Rare earth elements, including Eu, are increasingly used to design new electrode nanocomposites with enhanced electrocatalytic properties. Europium has been considered a significant lanthanide element with greater redox reaction behavior. We conducted a hydrothermal synthesis of Eu2O3@Cr2O3 and, for the first time, the acquired nanoparticles were used to modify CPE. The proposed Eu2O3@Cr2O3/CPE electrode was investigated in terms of its electrocatalytic properties and then used to develop an analytical method for detecting and quantifying L-DOPA. The proposed sensor offers a wide linear range (1–100 µM), high sensitivity (1.38 µA µM−1 cm−2) and a low detection limit (0.72 µM). The practical application of the proposed sensor was investigated by analyzing commercially available pharmaceutical tablets of L-DOPA. The corresponding results indicate the excellent potential of the Eu2O3@Cr2O3/CPE sensor for application in real-time L-DOPA detection.

Herein, a screen–printed diamond electrode (SPDE) coupled with a “point-of-care” platform (30 µL-drop concepts, single-drop-detection approach) was successfully applied for the electrochemical determination of pterostilbene (PTS). Cyclic voltammetry identified irreversible oxidation of PTS, where oxidation peak was shown to be strongly dependent on the pH of the working environmental. Although the proposition of the detailed electrochemical oxidation mechanism of PTS goes out of the scope of the present research, we have determined the most probable reactive site of our analyte, by utilizing DFT-based reactivity descriptors (Fukui functions). For electrochemical quantification of PTS, oxidation peak at 0.32 V (vs. Ag/AgCl) was followed in presence of 0.5 mol L−1 of Briton–Robinson buffer solution (pH = 9). Coupled with the optimized parameters of differential pulse voltammetry (DPV), SPDE detected PTS in two linear ranges (first range was from 0.011 to 0.912 µmol L−1; second range was from 0.912 to 4.420 µmol L−1), providing the LOD and LOQ on a nanomolar level (3.1 nmol L−1 and 10.0 nmol L−1, respectively). The selectivity of the optimized DPV method was found to be excellent, with the current changes of less than 7%, in the presence of ten times higher concentrations of the certain interferences. The practical applicability of the SPDE and single-drop-detection approach in dietary supplements (with a declared PTS content of 50 mg/tablet), with the recovery values ranging from 95 to 102%, shows that the developed method has high potential for precise and accurate PTS detection, as well as exceptional miniaturization possibilities of relevant equipment for on-site sensing.