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This paper deals with electrochemical insertion into a cathodic material. New results on modeling of the influence of a solid phase transformation on the shape of voltamograms are presented. The original experiments concern the insertion of sodium into carbon during the cathodic reduction of molten NaF at 1020 °C, but in the present manuscript emphasis on the theoretical aspects of the work is put. Phase transformations during electrochemical insertion are taken into account, with various values for parameters such as the thermodynamic biphase equilibrium potential, the compared diffusion and phase transformation kinetics, and the electrode thickness. The voltamograms calculated present very specific features; some of them have already been observed experimentally in literature.

A heterogeneous Fenton reaction using Iron alginate beads (Fe-AB) was evaluated for the removal of an N-heterocyclic compound indole-3-acetic acid (IAA), which ranked as uremic toxin and an herbicide derivative. The efficiency of the process was studied as a function of the experimental conditions: initial pH; H2O2dose, temperature, initial concentrations of IAA, and Iron alginate beads loading. Under the best experimental conditions: pH 3.0; H2O2dose = 9.8 mM; and [alginate beads] = 1.0 g L−1, it was possible to remove 100% of 0.11 mM IAA in 120 min in a batch reaction at 25°C. The experimental results indicate also that the use of this catalyst allows a significant removal of total organic carbon without significant leaching of Fe ions. A kinetic analysis showed that the removal of IAA followed a first-order kinetics model. In addition, the Fe-AB catalyst can be reused for successive runs, without significant loss of activity. [ABSTRACT FROM AUTHOR]

A novel gas diffusion–flow injection method has been developed for the rapid and sensitive determination of total inorganic carbon (TIC) in water. The method is based on the diffusion of CO2 across gas permeable membrane from a donor stream containing 0.1 M HCl to an acceptor stream of sodium acetate (10−5 mol l−1 and pH 10). The CO2 trapped in the acceptor stream passes through an electrochemical flow cell contains a tungsten oxide wire and a silver/silver chloride electrode, where it was sensitively detected. The parameters affecting the sensitivity of the electrode such as buffer concentration, pH, flow rate and injected volume were studied in detail. The electrode response was linear in the concentration range from 5 to 100 μg ml−1 CO32− with a correlation coefficient (R2) of 0.998. Precision (R.S.D.) was 1.42% for 20 μg ml−1 standard solution of CO32− (n=10). The detection limit was 0.20 μg ml−1 CO32−. The method was evaluated by the injection of real natural water samples and an average recovery of 100.1% was obtained. The sampling rate was 30 samples h−1. The method is simple, feasible with satisfactory accuracy and precision and thus could be used for monitoring TIC in water. [Copyright &y& Elsevier]

The electrochemical reduction of N-acylated imidates of a typical structure (Sch. 1) has been investigated by cyclic voltammetry and controlled potential electrolysis at mercury electrode in aprotic solvent. Electrodimerization occurs at the first wave and leads to the formation of 3a,6a-dihydro-oxazolo[5,4-d]oxazole 2 in good yields. Scheme 1. [ABSTRACT FROM AUTHOR]

An electrochemically synthetized nano-sensor based on molecularly imprinted polypyrrole (MIPPy) was successfully developed for the detection of 5-hydroxyindole-3-acetic acid (5-HIAA) in human biological fluids namely serum, urine, and plasma. The imprinted glassy carbon electrode was prepared by electropolymerisation of pyrrole via cyclic voltammetry (C.V). After completely leaching the imprinted molecules from the polymeric network, complementary cavities are created. The developed MIPPy sensor, under optimized conditions, shows a high sensitivity towards the target molecule (LOQ = 5 × 10 -11  M). Moreover, it presents a wide linear response in the range of 5 × 10 -11 - 5 × 10 -5  M (R 2  > 0.999) with a detection limit of 15 × 10 -12  M. In order to evaluate the selectivity of the MIPPy film, several structural analogues and compounds forming the real matrices were tested. The obtained results show an excellent recovery rate (between 98.86 and 101.52%) proving the promising application of the proposed nano-sensor in the detection of 5-HIAA in human biological fluids without any significant interference recorded., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

A simple protocol was proposed for the preparation of magnetic chitosan beads ZnFe 2 O 4 -CS via a co-precipitation method. The use of synthesized magnetic ZnFe 2 O 4 -CS beads as catalyst for the heterogeneous photo-Fenton treatment of chlordimeform insecticide (CDM) was evaluated. The photo-Fenton experiments were carried out with different synthesized catalysts by varying the molar ratio Zn/Fe in chitosan beads, the catalyst concentration and pH. Under optimal conditions using 1 g of ZnFe 2 O 4 -CS beads with a molar ratio Zn/Fe = 0.35 and at pH initial  = 3, a real wastewater doped with 20 mg L -1 of CDM was treated and complete removal of the insecticide was achieved after 7 min with a total TOC removal after 2 h of treatment. The generated carboxylic acids and ions during the photo-Fenton process were identified and quantified. The stability of the photocatalytic activity of the best catalyst in terms of pollutant removal, ZnFe 2 O 4 -CS(0.35) beads with a molar ratio Zn/Fe equal to 0.35, was satisfactory validated by four consecutive cycles. This optimal catalyst was characterized, before and after use, by Scanning Electron Microscopy/Energy Dispersive X-Ray Spectroscopy, X-Ray Powder Diffraction and Vibrating Sample Magnetometry analysis., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Iron-alginate beads (Fe-ABs) were successfully prepared by the ion-gelation method, and applied as heterogeneous Fenton catalysts for the removal of a malodorous compound 'indole'. Similarly, copper-enriched alginate beads (Cu-ABs) were synthesized and tested as like-Fenton catalyst, however, their application proved not to be effective for this purpose. Fe-ABs catalysts were characterized by FTIR, SEM, EDS and AAS spectroscopy. Results pointed out that the parameters affecting Fenton catalysis must be carefully chosen to avoid excessive iron release. Under optimal conditions, complete indole removal and considerably high reduction of TOC, without significant leaching was achieved. Indole decay followed a pseudo-first-order kinetics. The absolute rate constant for indole hydroxylation was 3.59×10(9) M(-1) s(-1), as determined by the competition kinetics method. Four reaction intermediates (Isatin, Dioxindole, Oxindole and Anthralinic acid) were identified by ULC/MS/MS analysis. Short-chain aliphatic carboxylic acids like formic, acetic, oxalic, maleic, oxamic and pyruvic acids were identified by ion exclusion chromatography and as end-products. Based on the identified by-products, a plausible mineralization pathway was proposed. Moreover, the catalyst was recovered quantitatively by simple filtration and reused for several times without significant loss of activity., (Copyright © 2015 Elsevier B.V. All rights reserved.)

A novel magnetic heterogeneous catalyst has been developed by incorporation of iron(II) and magnetic functionalized nanoparticles Fe3O4 in alginate beads with the aim of using them in the advanced Fenton oxidation of a malodorous compound (3 methyl-indole: 3-MI). The effects of significant operational parameters such as initial pH, oxidant concentration and catalyst amount were investigated and optimized for a better removal of 3-MI at initial concentration of 20mgL(-1). Besides, the catalyst stability was evaluated according to the iron leached into the aqueous solution. Results revealed that the parameters affecting Fenton catalysis must be carefully chosen to avoid excessive iron release. Under optimized conditions, the magnetic catalyst exhibited a good catalytic performance. Total removal of 3 methyl indole and a remarkable organic mineralization, without significant leaching of iron, were attained within 120min at pH 3.0 by using 0.4gL(-1) of Fe-MABs and 9.8mmolL(-1) of H2O2. The novel magnetic catalyst would be of potential application due to its high efficiency, easy recovery and good structural stability., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The performance of a molecularly imprinted polymer (MIP) as selective packing material for solid-phase extraction (SPE) of residual glibenclamide in an industrial process was investigated. MIP was prepared using 4-vinylpyridine as monomer, ethylenedimethacrylate as cross linker, 2,2'-azobis-2-methylpropionitrile as initiator and dimethyl formamide as porogen. Use of acetonitrile as a rebinding solvent allows good recognition of the glibenclamide template. It was found that this polymer can be used for determination of trace levels of glibenclamide with a recovery percentage that could reach 87.1 %. Furthermore, the synthesized MIP showed higher selectivity towards glibenclamide than other compounds such as glimepiride and metformin. The synthesized MIP enabled direct determination of the target contaminant after an enrichment step that allowed quantification of glibenclamide at a concentration as low as 0.016 mg L-1. Combination of high performance liquid chromatography with MIP-SPE could be successfully used for quality control of pharmaceuticals during the cleaning process in the production of dry drug forms.

A new simple gas diffusion flow injection method has been developed for the determination of thiomersal in biological samples. The method is based on cold vapor generation of monoatomic mercury from thiomersal reaction with acidic stannous chloride solution (0.6%) acting as reducing agent. The evolved mercury partially diffuses through a Teflon membrane into an acidic permanganate (2.25 × 10(-4) mol L(-1)) acceptor stream, where it is oxidized and re-converted to Hg(II). The resulting decrease in acceptor stream absorbance is sensitively monitored at 528 nm. Flow injection variable parameters such as reagents concentrations, injected volume, reactor length, temperature and flow rate were carefully investigated and optimized. The concentration-response relationship was linear over a concentration range of 1-30 mg L(-1) with a correlation coefficient greater than 0.99 and a good reproducibility (RSD<1.42%, n=6) at 10 mg L(-1). A detection limit of 0.07 mg L(-1) (S/N=3) and a sampling frequency of 5 samples h(-1) were obtained. The method was successfully applied for the determination of thiomersal in different types of vaccines and gave results in close agreement with those found by previously established HPLC method with no significant interference from vaccines matrices., (Copyright © 2012 Elsevier B.V. All rights reserved.)

The removal of rotenone from synthetic and real wastewaters using modified activated carbons has been investigated. In order to enhance the removal capacity of rotenone, activated carbon was chemically modified through impregnation with NH(3) and (NH(4))(2)S(2)O(8) solutions. The resulting carbons were found to present different surface chemistries, while possessing similar textural properties. The adsorption data obtained at 298 K, on plain and modified carbons were well represented by the Langmuir isotherm model (R(2)>0.997). The highest adsorption capacity (Q(m)=270.3 mg g(-1)) was obtained with the ammonia-treated activated carbon. The relative effect of different surface groups on adsorption capacities were found to be in accordance with the pi-pi dispersive interaction model. The adsorption kinetic models have provided useful insights into rotenone adsorption mechanism. It was concluded that rotenone sorption process followed pseudo-second order model and was controlled by intra-particle diffusion mechanism with a significant contribution of film diffusion. The successful adsorptive removal of rotenone, from real wastewater samples on fixed bed columns, have demonstrated the suitability of this method as an effective alternative solution for the treatment of contaminated wastewaters., (Copyright 2010 Elsevier B.V. All rights reserved.)

A two in one attempt for the removal of tartrazine and metal ions on activated carbon has been developed. The method was based on the modification of activated carbon with tartrazine then its application for the removal of Pb(II), Cd(II) and Cr(III) ions at different pH values. Tartrazine adsorption data were modelled using both Langmuir and Freundlich classical adsorption isotherms. The adsorption capacities qm were 121.3, 67 and 56.7mgg(-1) at initial pH values of 1.0, 6.0 and 10, respectively. The adsorption of tartrazine onto activated carbon followed second-order kinetic model. The equilibrium time was found to be 240min at pH 1.0 and 120min at pH 10 for 500mgL(-1) tartrazine concentration. A maximum removal of 85% was obtained after 1h of contact time. The presence of tartrazine as modifier enhances attractive electrostatic interactions between metal ions and carbon surface. The adsorption capacity for Pb(II), Cd(II) and Cr(III) ions has been improved with respect to non-modified carbon reaching a maximum of 140%. The adsorption capacity was found to be a pH dependent for both modified and non-modified carbon with a greater adsorption at higher pH values except for Cr(III). The enhancement percent of Pb(II), Cd(II) and Cr(III) at different pH values was varied from 28% to 140% with respect to non-modified carbon. The amount of metal ions adsorbed using static regime was 11-40% higher than that with dynamic mode. The difference between adsorption capacities could be attributed to the applied flow rate.

A flow-injection method for measuring the peroxide value (PV, mequiv. O2 kg(-1)) in edible oils is described. The technique is based on spectrophotometric monitoring at 660 nm of methylene blue (MB), generated from leucomethylene blue (LMB) oxidation with peroxides present in oil samples. After being optimized, the method was validated in terms of linearity, precision sensitivity and recovery. Linear calibration graph was obtained in the range 0.1-5 mequiv. O2 kg(-1), with a detection limit (S/N=3) of 0.014 mequiv. O2 kg(-1). The precision of the method (R.S.D., n=9) for within and between-days is better than 1.5% and 2.2%, respectively at 0.4 mequiv. O2 kg(-1). The method was applied successfully to the determination of PV in six edible oil samples, and compared to the classical official method. Using the linear regression test, Student's t-test and variance ratio F-test, there was no significant difference between the compared methods. The proposed method is accurate, simple, cheap and could be used to control edible oil rancidity with a high sample throughputs (30 samples h(-1)).

The differential pulse voltammetric (DPV) determination of trimebutine (TMB) was achieved at a glassy carbon electrode in acetonitrile/0.1 M LiClO4. Trimebutine gave two irreversible, diffusion controlled peaks at 740 and 1318 mV versus Ag/AgCl reference electrode, respectively. The second oxidation peak was used to determine trimebutine concentrations in the range 1-50 microg ml(-1) with a detection limit (3sigmam) of 0.3 microg ml(-1). Precision of the method (RSD, n=6) within- and between-days obtained from six determinations at 5 microg ml(-1) was found to be 0.7 and 1.1%, respectively. The method was successfully applied to the quantitation of TMB in granule dosage form (Debridat) and recoveries between 98.4 and 101% were obtained. Excipients did not interfere with the assay and the results agreed well with those determined by previously established HPLC method.