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This work describes the synthesis and application of a novel magnetic metal-organic framework (MOF) [([Fe.sub.3][O.sub.4]-2,5-dimercapto-1,3,4-thiadiazole)/[Cu.sub.3] [(benzene-1,3,5-tricarboxylate).sub.2]] to preconcentrate trace amounts of Cd(II), Pb(II), and Zn(II) ions. A Box-Behnken design was used to find the parameters affecting the preconcentration procedure through response surface methodology. Three variables including sorption time, amount of the magnetic sorbent, and sample pH were selected as affecting factors in the sorption step, and four parameters including type, volume, concentration of the eluent, and elution time were selected in the elution step for the optimization study. These values were 33 mg, 11 min, 5.7 EDTA, 4.3 mL, 0.64 mol [L.sup.-1] EDTA solution, 16 min, for amount of the magnetic sorbent, sorption time, sample pH, type, volume, and concentration of the eluent, and elution time, respectively. Following the sorption and elution steps, the ions were quantified by FAAS. The limits of detection were 0.10, 0.15, and 0.75 ng [mL.sup.-1] for Cd(II), Zn(II), and Pb(II) ions, respectively. The relative standard deviations (RSD) of the method were less than 8.3% for five separate batch experiments in the determination of 25 µg [L.sup.-1] of Cd(II), Zn(II), and Pb(II) ions. The sorption capacity of the magnetic MOF nanocomposite was 155 mg [g.sup.-1] for Cd(II), 173 mg [g.sup.-1] for Pb(II), and 190 mg [g.sup.-1] for Zn(II). Finally, the magnetic MOF nanocomposite was successfully applied to rapidly extract trace amounts of heavy metal ions in baby food samples. Key words: magnetic metal-organic frame work nanocomposite, heavy metal ions, extraction, baby food samples. Les presents travaux decrivent la synthese et l'application d'un nouveau reseau metallo-organique [([Fe.sub.3][O.sub.4]-2,5-dimercapto-1,3,4-thiadiazole)/[Cu.sub.3][(benzene-1,3,5-tricarboxylate).sub.2]] en vue de la preconcentration des ions de Cd(II), de Pb(II) et de Zn(II) a l'etat de trace. Nous avons utilise un plan d'etude de Box-Behnken afin de trouver, au moyen de la methodologie de surface des reponses, les parametres influant sur la procedure de preconcentration. Trois variables, soit le temps de sorption, la quantite de sorbant magnetique et le pH de l'echantillon, ont ete selectionnees comme facteurs d'influence dans l'etape de sorption et quatre parametres, soit le type, le volume, la concentration, l'eluant et le temps d'elution, ont ete selectionnes dans l'etape de l'elution aux fins d'etude de l'optimisation. Les valeurs de la quantite de sorbant magnetique, de temps de sorption, de pH de l'echantillon, de type, de volume et de concentration de l'eluant, et de temps d'elution etaient respectivement 33 mg, minutes, 5,7, EDTA, 4,3 mL, solution d'EDTAa 0,64 mol [L.sup.-1] et 16 minutes. Apres les etapes de sorption et d'elution, les ions ont ete quantifies par spectrometrie d'absorption atomique a atomisation par flamme (FAAS). Les limites de detection etaient respectivement 0,10, 0,15 et 0,75 ng [mL.sup.-1] pour les ions de Cd(II), de Zn(II) et de Pb(II). Les coefficients de variation (CV) de la methode etaient inferieurs a 8,3% dans les cinq series d'experiences ayant permis de doser les ions de Cd(II), de Zn(II) et de Pb(II) a 25 µg [L.sup.-1]. La capacite de sorption du reseau metallo-organique nanocomposite magnetique etait de 155 mg [g.sup.-1] pour le Cd(II), de 173 mg [g.sup.-1] pour le Pb(II) et de 190 mg [g.sup.-1] pour le Zn(II). Enfin, le reseau metallo-organique nanocomposite magnetique a ete utilise avec succes pour extraire rapidement les metaux lourds presents a l'etat de trace dans des echantillons d'aliments pour nourrisson. [Traduit par la Redaction] Mots-cles: reseau metallo-organique nanocomposite magnetique, ions de metaux lourds, extraction, echantillon d'aliments pour nourrisson., Introduction Heavy metals are toxic pollutants that exist widely in wastewaters, and their presence concerns industries and environmental organizations all over the world. Most of these pollutants are severely toxic [...]

In this paper, switchable solvent-based liquid phase microextraction was developed for preconcentration of cadmium ions and its detection by flame atomic absorption spectrometry. 2,9-dimethyl-1,10-phenanthroline (neocuproine) was used as a complexing agent in the developed sample preparation method. Conversion features of triethylamine and protonated triethylamine bicarbonate were used as a switchable solvent pair. Protonated triethylamine bicarbonate as polar form of switchable polarity solvent was successfully synthesized from triethylamine via proton transfer reaction and used for microextraction of hydrophobic cadmium complex with 2,9-dimethyl-1,10-phenanthroline at pH 7.0. The factors influencing the extraction procedure were investigated and optimized. Under the optimized conditions, limit of detection, limit of quantification, and enrichment factor for the proposed method were 0.02, 0.1 µg L, and 54.2, respectively. The calibration curve was linear in the range of 0.1-60 µg L with a correlation of determination ( r ) of 0.99. The relative standard deviation for determination of 40 µg L of Cd (II) was 3.1% ( n = 6). The intraday and inter-day precisions for real samples analysis were in the range of 4.4-5.6 and 4.9-5.7%, respectively. The proposed method was applied for the determination of cadmium in baby food samples with satisfactory analytical results. In comparison with other methods, the proposed method is very easy, rapid, simple, and sensitive for determination of cadmium at trace levels in complex matrices. [ABSTRACT FROM AUTHOR]

A heterogeneous material composed of MCM-48/H5PW10V2O40 was produced and used as an efficient, eco-friendly and highly recyclable catalyst for the one-pot and multicomponent synthesis of 3,4-dihydroquinoxalin-2-amine, diazepine-tetrazole and benzodiazepine-2-carboxamide derivatives in aqueous media and at room temperature with high yields in short reaction times (40-60 min). The recoverable catalyst was easily recycled at least five times without any loss of catalytic activity. The structures of obtained products were confirmed using 1H NMR and 13C NMR spectra. [ABSTRACT FROM AUTHOR]

A magnetic inorganic-organic nanohybrid material (HPA/TPI-Fe3O4 NPs) was produced as an efficient, highly recyclable and eco-friendly catalyst for the one-pot multi-component synthesis of malonamide and 2,3,4,5-tetrahydrobenzo[ b][1,4]oxazepine derivatives with high yields in short reaction times (25-35 min) in aqueous media at room temperature. The nanohybrid catalyst was prepared by the chemical anchoring of H6P2W18O62 onto the surface of modified Fe3O4 nanoparticles (NPs) with N-[3-(triethoxysilyl)propyl]isonicotinamide (TPI) linker. The magnetic recoverable catalyst was easily recycled at least ten times without any loss of catalytic activity. [ABSTRACT FROM AUTHOR]

The yolk-shell Fe3O4-polyaniline for decoration of Pd-Ni nanoparticles (yolk-shell Fe3O4-PANI/Pd-Ni) were synthesized and used as a new electrocatalyst for oxidation of formic acid. The yolk-shell Fe3O4-PANI/Pd-Ni catalyst provided superior catalyst performance for formic acid oxidation in H2SO4 aqueous solution. These yolk-shell Fe3O4-PANI/Pd-Ni catalysts were found to be more resistant to deactivation in the oxidation of formic acid than yolk-shell Fe3O4-PANI/Pd and Pd/C and to consistently show better long-term performances. The enhanced catalytic performance may arise from the unique structure and surface properties of the yolk-shell Fe3O4-PANI and bi-functional effect, which process extraordinary promotional effect on Pd catalyst. In the current study, a highly efficient catalyst based on Pd-Ni nanoparticles supported on yolk-shell Fe3O4-polyaniline (yolk-shell Fe3O4-PANI/Pd-Ni) was synthesized and used as a new electrocatalyst for the oxidation of formic acid. The electrochemical studies showed that this new catalyst provided superior catalyst performance for formic acid oxidation. The enhanced catalytic performance may arise from the unique structure and surface properties of the yolk-shell Fe3O4-PANI and bi-functional effect, which process extraordinary promotional effect on Pd catalyst. [ABSTRACT FROM AUTHOR]

Gold and silver nanoparticles (NPs) are shown to exert a positive effect on the chemiluminescence (CL) reaction of permanganate aldehydes. Interestingly, between various shapes examined, Au nanoprisms have the highest beneficial effect. This effect is even more notable in the presence of sodiumdodecyl sulfate (SDS) surfactant. UV-vis spectra and transmission electron microscopy were used to characterize the NP shapes and sizes. Furthermore, it was observed that iron(III) ions can slightly increase CL emission of this system. This intensification is very effective in the presence of fluoride ions (F-). These observations formthe basis of themethod for the high sensitive determination of F- in the 6-1200nmol L-1 concentration range, with a detection limit of 2.1 nmol L-1. The proposed method has good precision and was satisfactorily used in the selective determination of low concentrations of fluoride ion in real samples. [ABSTRACT FROM AUTHOR]

In the current work, a new version of rank annihilation factor analysis was developed to circumvent the rank deficiency problem in multivariate data measurements. Simultaneous determination of dissociation constant and concentration of monoprotic acids was performed by applying model-based rank annihilation factor analysis on variation matrices of spectrophotometric acid-base titrations data. Variation matrices can be obtained by subtracting first row of data matrix from all rows of the main data matrix. This method uses variation matrices instead of multivariate spectrophotometric acid-base titrations matrices to circumvent the rank deficiency problem in the rank quantitation step. The applicability of this approach was evaluated by simulated data at first stage, then the binary mixtures of ascorbic and sorbic acids as model compounds were investigated by the proposed method. At the end, the proposed method was successfully applied for resolving the ascorbic and sorbic acid in an orange juice real sample. Therefore, unique results were achieved by applying rank annihilation factor analysis on variation matrix and using hard soft model combination advantage without any problem and difficulty in rank determination. [ABSTRACT FROM AUTHOR]

A sensitive and simple method based on the fluorescence quenching CdS quantum dots (QDs) was reported for the determination of copper(Cu2+) and nickel (Ni2+) in water samples. Water-soluble and biocompatible thioglycolic acid- capped CdSQDs was synthesized by one step process, then characterized by fluorescence, absorption spectroscopy and transmission electron microscopy (TEM). The fluorescence intensity of synthesized QDsremarkably decreased in the presence of Cu2+ and Ni2+ ions. The emission of CdSQDs had a linear decreasing relationship with Cu2+ and Ni2+ concentration in the range of 0.6 to 200 and 1 to 250 ng mL-1 with detection limits of 0.15 and 0.4 ng mL-1, respectively. Other potentially interfering ions such as iron, sodium, potassium, calcium, and magnesium ions did not affect the luminescence. The method showed good sensitivity and was satisfactorily applied to the determination of Cu2+ and Ni2+ contamination in real water samples, obtained from Nahand dam, Karkaj and Azarshahr well, tab and mineral waters. [ABSTRACT FROM AUTHOR]

A heterogeneous material composed of MCM-48/H5PW10V2O40 was produced and used as an efficient, eco-friendly and highly recyclable catalyst for the one-pot and multicomponent synthesis of 3,4-dihydroquinoxalin-2-amine, diazepine-tetrazole and benzodiazepine-2-carboxamide derivatives in aqueous media and at room temperature with high yields in short reaction times (40-60 min). The recoverable catalyst was easily recycled at least five times without any loss of catalytic activity. The structures of obtained products were confirmed using 1H NMR and 13C NMR spectra. [ABSTRACT FROM AUTHOR]

Gold and silver nanoparticles (NPs) are shown to exert a positive effect on the chemiluminescence (CL) reaction of permanganate aldehydes. Interestingly, between various shapes examined, Au nanoprisms have the highest beneficial effect. This effect is even more notable in the presence of sodium dodecyl sulfate (SDS) surfactant. UV-vis spectra and transmission electron microscopy were used to characterize the NP shapes and sizes. Furthermore, it was observed that iron(III) ions can slightly increase CL emission of this system. This intensification is very effective in the presence of fluoride ions (F(-)). These observations form the basis of the method for the high sensitive determination of F(-) in the 6-1200 nmol L(-1) concentration range, with a detection limit of 2.1 nmol L(-1). The proposed method has good precision and was satisfactorily used in the selective determination of low concentrations of fluoride ion in real samples., (Copyright © 2015 John Wiley & Sons, Ltd.)