An electrochemical approach for the prediction of Δ9-tetrahydrocannabinolic acid and total cannabinoid content in Cannabis sativa L.

Two electrochemical sensors are proposed here for the first time for the fast screening of cannabinoids in Cannabis sativa L. plant material (inflorescences). The accurate control of cannabinoid content is important for discriminating between recreational, i.e. illegal, and fibre-type C. sativa samples, which differ mainly according to the amount of Δ9-tetrahydrocannabinol (Δ9-THC) and Δ9-tetrahydrocannabinolic acid (Δ9-THCA). Two screen printed electrodes obtained using different electrode materials were tested for the analysis of extracts from recreational and fibre-type C. sativa and their performance was compared with a consolidated method based on high-performance liquid chromatography (HPLC). The voltammetric responses recorded in the different samples reflected the compositional differences of the recreational and fibre-type extracts in accordance with the results of HPLC analyses. Moreover, the quantification of Δ9-THCA and the total cannabinoid content on the basis of the intensity of the peaks of the voltammograms was possible through a simple and fast electrochemical procedure.

A Continuous Extraction Protocol for the Characterisation of a Sustainably Produced Natural Indigo Pigment.

The sustainable industrial production of indigo necessitates a unique extraction process to separate the plant-derived compounds. Calcium compounds are added to encourage hydrolysis of these precursors and to facilitate the isolation of the final form, resulting in an organic-inorganic composite pigment with unspecified characteristics. In this study, we devised a continuous solvent extraction procedure to fractionate the organic indigoid phase within the composite pigment. Overcoming challenges posed by limited solubility in the common organic solvents, this method allows for the analysis of individual fractions, significantly enhancing resolution. Comprehensive characterisation using spectroscopic analysis, thermogravimetry, and UHPLC-MS/MS revealed the potential for quantifying primary components of the natural pigment and distinct differentiation from the synthetic dye. This approach also holds promise for establishing robust manufacturing practices in the industrial production of natural indigo.

Fast Analysis of Caffeic Acid-Related Molecules in Instant Coffee by Reusable Sonogel-Carbon Electrodes.

Reusable Sonogel-Carbon electrodes containing carbon black (SNGC-CB) have been used for the electrochemical analysis of caffeic acid (CA) in real matrices. Measurements were firstly performed in standard solutions, in which SNGC-CB electrodes allowed the electrochemical determination of CA with high sensitivity and low limit of detection, equal to 0.76 µM. The presence of CB nanostructures in the formulation led to improved performances with respect to pristine SNGC electrodes. Then, measurements were performed in four instant coffees of different brands. A comparison between the results obtained by electrochemical, chromatographic and spectroscopic methods showed that SBGC-CB electrodes represent a simple and economic tool for the rapid assessment of caffeic acid-related molecules in instant coffees.

Toward the Development of Combined Artificial Sensing Systems for Food Quality Evaluation: A Review on the Application of Data Fusion of Electronic Noses, Electronic Tongues and Electronic Eyes.

Devices known as electronic noses (ENs), electronic tongues (ETs), and electronic eyes (EEs) have been developed in recent years in the in situ study of real matrices with little or no manipulation of the sample at all. The final goal could be the evaluation of overall quality parameters such as sensory features, indicated by the "smell", "taste", and "color" of the sample under investigation or in the quantitative detection of analytes. The output of these sensing systems can be analyzed using multivariate data analysis strategies to relate specific patterns in the signals with the required information. In addition, using suitable data-fusion techniques, the combination of data collected from ETs, ENs, and EEs can provide more accurate information about the sample than any of the individual sensing devices. This review's purpose is to collect recent advances in the development of combined ET, EN, and EE systems for assessing food quality, paying particular attention to the different data-fusion strategies applied.

Simultaneous Detection of Glucose and Fructose in Synthetic Musts by Multivariate Analysis of Silica-Based Amperometric Sensor Signals.

Silica-based electrodes which permanently include a graphite/Au nanoparticles composite were tested for non-enzymatic detection of glucose and fructose. The composite material showed an effective electrocatalytic activity, to achieve the oxidation of the two analytes at quite low potential values and with good linearity. Reduced surface passivation was observed even in presence of organic species normally constituting real samples. Electrochemical responses were systematically recorded in cyclic voltammetry and differential pulse voltammetry by analysing 99 solutions containing glucose and fructose at different concentration values. The analysed samples consisted both in glucose and fructose aqueous solutions at pH 12 and in solutions of synthetic musts of red grapes, to test the feasibility of the approach in a real frame. Multivariate exploratory analyses of the electrochemical signals were performed using the Principal Component Analysis (PCA). This gave evidence of the effectiveness of the chemometric approach to study the electrochemical sensor responses. Thanks to PCA, it was possible to highlight the different contributions of glucose and fructose to the voltammetric signal, allowing their selective determination.

Development of an electrochemical sensor based on carbon black for the detection of cannabidiol in vegetable extracts.

A glassy carbon electrode chemically modified with a carbon black coating is proposed here for the rapid and portable determination of cannabidiol (CBD) in a commercial Cannabis seed oil and in fibre-type Cannabis sativa L. leaves. The mechanism of CBD oxidation was studied in relation to simpler phenyl derivatives bearing the same electroactive group, namely resorcinol and 2-methylresorcinol. These molecules also allowed us to determine the best conditions for the electrochemical detection of CBD, as to the pH value and to the best solvent mixture to use. Carbon black was chosen among nanostructured carbon-based materials owing to its outstanding features as an electrode modifier for analyte detection. The performance of the modified electrode was determined by flow injection analyses of standard solutions of CBD, obtaining a linear correlation between the oxidation current and the analyte concentration; the sensor response is characterised by suitable repeatability and reproducibility. The analysis of commercial products by the standard addition method allowed us to ascertain the accuracy of the sensor for the detection of CBD in real samples.

From solid state to in vitro anticancer activity of copper(II) compounds with electronically-modulated NNO Schiff base ligands.

The copper(ii) complexes of general formula [Cu(GL)(Cl)] (1-3, G = OMe, H and NO2, respectively), bearing tridentate Schiff base ligands (GL-) and a chloride as a fourth labile one, are here reported. The Schiff bases derive from the monocondensation of ethylenediamine and substituted salicylaldehyde, where the electronic properties are modulated by the releasing or withdrawing power of the G group. The compounds were structurally characterized through single crystal Synchrotron X-ray diffraction experiments in the solid state, revealing that 1 (OMe) and 2 (H) adopt a dimeric assembly [Cu(µ-Cl)(GL)]2 through apical interaction of the chloride ions of two monomeric units, while 3 embraces a 1D polymeric chain structure [Cu(µ-Cl)(NO2L)]n with a similar bridging fashion, all supported by extended intramolecular or intrachain hydrogen bonds. The redox properties of the complexes were also studied by cyclic voltammetry with no marked effect of the substituent on the potential of the CuII/CuI redox system. UV/Vis spectroscopic studies in mimicked physiological conditions highlighted the intactness and stability of the coordinated NNO tridentate ligand in 1-3 and the lability of the coordinated chloride ion with the formation of the aquo-complexes [Cu(GL)(H2O)]+ in aqueous solution, as confirmed by conductance measurements with a 1 : 1 electrolyte molar conductivity. In vitro tests on cell viability were conducted on malignant cell lines typical for their poor prognosis and curability, revealing time-dependent and differential cytotoxicity given by the substituent G. All compounds were capable of formation of intracellular reactive oxygen species and DNA intercalation, acting as nuclease and producing double-strand DNA breaks. This is especially effective for 3 (NO2), which revealed the highest anticancer activity against malignant triple-negative breast cancer MDA-MB-231 cells, with a two-to-four-fold cytotoxicity enhancement with respect to 1 (OMe) and 2 (H), and, most important, substantial differentiation of cytotoxicity with respect to healthy endothelial HUVEC cell line.

Selective Formation, Reactivity, Redox and Magnetic Properties of MnIII and FeIII Dinuclear Complexes with Shortened Salen-Type Schiff Base Ligands.

The reactivity of the shortened salen-type ligands H3salmp, H2salmen and H2sal(p-X)ben with variable para-substituent on the central aromatic ring (X = tBu, Me, H, F, Cl, CF3, NO2) towards the trivalent metal ions manganese(III) and iron(III) is presented. The selective formation of the dinuclear complexes [M2(µ-salmp)2], M = Mn (1a), Fe (2a), [M2(µ-salmen)2(µ-OR)2)], R = Et, Me, H and M = Mn (3a-c) or Fe (4a-c), and (M2(µ-sal[p-X]ben)2(µ-OMe)2), X = tBu, Me, H, F, Cl, CF3, NO2 and M = Mn (5a-g) or Fe (6a-g), could be identified by reaction of the Schiff bases with metal salts and the base NEt3, and their characterization through elemental analysis, infrared spectroscopy, mass spectrometry and single-crystal X-ray diffraction of 2a·2AcOEt, 2a·2CH3CN and 3c·2DMF was performed. In the case of iron(III) and H3salmp, when using NaOH as a base instead of NEt3, the dinuclear complexes [Fe2(µ-salmp)(µ-OR)(salim)2], R = Me, H (2b,c) could be isolated and spectroscopically characterized, including the crystal structure of 2b·1.5H2O, which showed that rupture of one salmp3- to two coordinated salim- ligands and release of one salH molecule occurred. The same hydrolytic tendency could be identified with sal(p-X)ben ligands in the case of iron(III) also by using NEt3 or upon standing in solution, while manganese(III) did not promote such a C-N bond breakage. Cyclic voltammetry studies were performed for 3b, 4b, 5a and 6a, revealing that the iron(III) complexes can be irreversibly reduced to the mixed-valence FeIIFeIII and FeII2 dinuclear species, while the manganese(III) derivatives can be reversibly oxidized to either the mixed-valence MnIIIMnIV or to the MnIV2 dinuclear species. The super-exchange interaction between the metal centers, mediated by the bridging ligands, resulted in being antiferromagnetic (AFM) for the selected dinuclear compounds 3b, 4b, 5a, 5e,5f, 6a and 6e. The coupling constants J (-2JS1·S2 formalism) had values around -13 cm-1 for manganese(III) compounds, among the largest AFM coupling constants reported so far for dinuclear MnIII2 derivatives, while values between -3 and -10 cm-1 were obtained for iron(III) compounds.

Data fusion of electronic eye and electronic tongue signals to monitor grape ripening.

Two separate artificial sensors, an electronic eye (EE) and an electronic tongue (ET), were recently developed to monitor grape ripening based on the analysis of must. The aim of this research is to exploit the complementary information obtained by means of EE and ET sensing systems using different data fusion strategies, in order to develop an integrated device able to quickly and easily quantify the physico-chemical parameters that are used to assess phenolic ripeness. To this purpose, both low-level and mid-level data fusion approaches were investigated. Partial Least Squares (PLS) regression was applied to the fused data, with the aim of relating the information brought by the two sensors with twelve physico-chemical parameters measured on the must samples by standard analytical methods. The results achieved with mid-level data fusion outperformed those obtained using EE and ET separately, and highlighted that both the artificial sensors have made a significant contribution to the prediction of each one of the considered physico-chemical parameters.

Optoelectronic Properties of A-π-D-π-A Thiophene-Based Materials with a Dithienosilole Core: An Experimental and Theoretical Study.

Two A-π-D-π-A thiophene-based small molecules with a central dithienosilole core and dicyanovinyl (DCV) end groups were synthesized. These compounds differ only by the presence of alkyl and alkylsulfanyl chains, respectively, on the thiophene beta positions. Computational data together with the spectroscopic and electrochemical findings (obtained by means of absorption, steady-state/time-resolved emission techniques, and cyclic voltammetry) revealed that both molecules possess low electronic and optical band gaps, broad absorption spectra, and good stability both in p and n-doping states, which make them suitable for optoelectronic applications. In both compounds, the HOMO-LUMO transition involves an intramolecular charge transfer from the electron-donor dithienosilole unit to the two terminal electron-acceptor DCV groups. A marked positive emission solvatochromism was observed for both molecules and was interpreted on the basis of the symmetry breaking in the S1 excited state. The two synthesized compounds were also compared to their shorter precursors and to similar oligothiophenes to understand how the nature of the building block influences the characteristics of the final materials. Furthermore, it was possible to better understand the contribution of the sulfur atom in modulating the optical properties of the small molecules studied.

Determination of polyphenol content and colour index in wines through PEDOT-modified electrodes.

Poly(3,4-ethylenedioxythiophene)-modified electrodes have been used for the estimation of the polyphenolic content and of the colour index of different samples of wines. Synthetic wine solutions, prepared with different amount of oenocyanins, have been analysed spectrophotometrically and electrochemically in order to find a correlation between the total polyphenolic content or colour index and the current peak. The regression curves obtained have been used as external calibration lines for the analysis of several commercial wines, ranging from white to dark red wines. In this way, a rapid estimation of the total polyphenolic content and of the colour index may be accomplished from a single voltammetric measurement. Furthermore, principal component analysis has also been used to evaluate the effect of total polyphenolic content and colour index on the whole voltammetric signals within a selected potential range, both for the synthetic solutions and for the commercial products. Graphical abstract Electrochemical sensors for the rapid determination of colour index and polyphenol content in wines.

Ti metal electrode as an unconventional amperometric sensor for determination of Au(III) species.

The control of the noble metal concentration is crucial in order to increase the efficiency of hydrometallurgic processes in mining and in the recovery of precious materials from electronic waste. The present study is devoted to the development of an effective procedure for the quantification of Au(III) species dissolved in aqueous solutions, similar real complex matrices included. In particular, a novel electrode system based on Ti has been studied. This electrode material is still poorly investigated in the framework of electroanalysis, despite its lack of sensitivity to common interfering species, such as oxygen; hence, the determination of metal species can be carried out without performing deaeration of the solution. In addition, the interfering effect due to the presence of other heavy metal ions, such as Ag, Fe and Pb, has been minimised by a proper choice of the conditions adopted for the amperometric measurements. Ti electrodes exhibit reproducible electrochemical responses, even in the presence of high concentration of organic fouling species typical of biosorption processes.

Development of a sensor system for the determination of sanitary quality of grapes.

n instrument for the automatic quantification of glycerol in grapes has been developed. We verify here that this analyte can be used as a benchmark of a serious disease affecting the grapevines, namely Botrytis cinerea. The core of the instrument is an amperometric biosensor consisting of a disposable screen printed electrode, generating the analytical signal thanks to a bi-enzymatic process involving glycerol dehydrogenase and diaphorase. The full automation of the analysis is realised by three micropumps and a microprocessor under control of a personal computer. The pumps allow the correct and constant dilution of the grape juice with a buffer solution also containing [Fe(CN)6]3- redox mediator and the injection of NAD+ cofactor when the baseline signal reaches a steady state; the instrument leads to automated reading of the analytical signal and the consequent data treatment. Although the analytical method is based on an amperometric technique that, owing to heavy matrix effects, usually requires an internal calibration, the analyses indicate that a unique external calibration is suitable for giving accurate responses for any grapes, both white and black ones.

Graphene-modified electrode. Determination of hydrogen peroxide at high concentrations.

A gold electrode partially coated by graphene multilayer is developed and tested with respect to high concentrations of hydrogen peroxide. The effective use of conventional electrode materials for the determination of such an analyte by anodic oxidation or cathodic reduction is prevented by the occurrence of adsorptions fouling the electrode surface. This prevents reliable and repeatable voltammetric curves for being recorded and serious problems arise in quantitative analysis via amperometry. The gold-graphene electrode is shown to be effective in quantitative evaluation, by cathodic reduction, of hydrogen peroxide at concentration levels that are of interest in an industrial. Acid, neutral, and basic pH values have been tested through correct adjustment of a Britton Robinson buffer. The experiments have been performed both by cyclic voltammetry and with amperometry at constant potential in unstirred solution. The latter technique has been employed in drawing a calibration linear plot. In particular, the performances of the developed electrode system have been compared with those of both pure gold and pure graphene electrode materials. The bi-component electrode was more sensitive; co-catalytic action by the combination of the two components is hypothesised. The system is stable over many potential cycles, as checked by surface-enhanced Raman spectra recorded over time.

3-methylthiophene self-assembled monolayers on planar and nanoparticle Au surfaces.

In this article the adsorption of 3-methylthiophene on planar and nanoparticle Au surfaces is investigated. The resulting systems are compared with a benchmark system based on 1-decanethiol. The characterization data collected evidence the formation of a packed 3-methylthiophene SAM on the planar surface. In particular, spectroscopic investigations suggest that 3-methylthiophene aromatic system is not adsorbed on the surface through the pi-electron system but rather through the S atom alone. On the other hand, the behavior of 3-methylthiophene on nanoparticle surfaces is notably different from that of the alkanethiol. Only a limited fraction of the surface of Au nanoparticles results to be actually coated after purification; this notwithstanding, the nanoparticle growth seems to be strongly influenced by the presence of such a labile encapsulating agent.

A study of the dielectric behaviour and the liquid structure of a ternary solvent system.

The static dielectric constant of the [DMF(1) + ME(2) + DME(3)] ternary mixtures was measured as a function of temperature (25 < or = t/degrees C < or = 80) and composition, over the whole mole fraction range 0 < or = chi,chi2,chi3 < or = 1. The experimental values were processed by an empirical equation accounting for the dependence epsilon = epsilon(T, phi(i)), where phi(t) is the volume fraction of the components. A comparison between calculated and experimental data shows that this fitting relationship can be effectively employed to predict epsilon values in correspondence to experimental data gaps. Starting from the experimental measurements, some derived quantities such as molar polarisation (P), and excess counterpart (PE) were obtained. Both the excess properties, epsilonE and PE, take values partly positive and partly negative under all experimental conditions. The values of the excess quantities are indicative of the presence of specific interactions among different components in the mixtures.

Beta-functionalised polythiophenes as microelectrode modifiers in low conductive media.

A study on polythiophene coated microelectrodes is reported, the goal being that of checking the capability of these electrochemical systems to work in low conductive media. The possibility of electrochemically p-doping the polymer in the presence of very low concentrations or even in the absence of supporting electrolyte in the solution is ascertained, opening the way to the use of similar systems in pure solvent media. This result is obtained in such conditions that the presence of residual charges--and corresponding counterions--trapped inside the film coating can be reasonably hypothesised.

Temperature and composition dependence of the refractive indices of the 2-chloroethanol + 2-methoxyethanol binary mixtures.

Measurements of the refractive index n for the binary mixtures 2-chloroethanol + 2-methoxyethanol in the 0 < or = t/degree C < or = 70 temperature range have been carried out with the purpose of checking the capability of empirical models to express physical quantity as a function of temperature and volume fraction, both separately and together, i.e., in a two independent variables expression. Furthermore, the experimental data have been used to calculate excess properties such as the excess refractive index, the excess molar refraction, and the excess Kirkwood parameter delta g over the whole composition range. The quantities obtained have been discussed and interpreted in terms of the type and nature of the specific intermolecular interactions between the components.