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1.
This paper reports the optimized synthesis of zinc molybdates by the hydrothermal method and the combination of ZnMoO4 and peroxymonosulfate (PMS) under UV irradiation for the degradation of pirimicarb. The as‐prepared ZnMoO4 photocatalyst was characterized using X‐ray diffraction, scanning electron microscopy, X‐ray photoelectron spectroscopy and UV–visible diffuse reflectance spectroscopy. The effects of operational parameters in the ZnMoO4/PMS/UV system were evaluated and the results indicated the highest performance is achieved with pH = 9.0, 1 mM PMS and 1 g l?1 ZnMoO4. The degradation efficiency of pirimicarb was 98% after 3 h in the photocatalytic process. A photodegradation mechanism is proposed based on scavenger and electron spin resonance studies to decide the main active species and by using chromatography–mass spectrometry to identify the major intermediates. Pirimicarb degradation is found to be mainly driven by holes and ?O2? radicals, with the contribution of ?OH and SO4?? radicals enhancing the process in the tested catalytic system. The mechanism is proposed involving two routes, dealkylation and decarbamoylation. Lastly, the zinc molybdate photocatalyst is shown to be stable, reusable and efficient in the removal of pirimicarb from real water samples in the presence of PMS, demonstrating potential application in the treatment of contaminated and/or environmental water.  相似文献   

2.
A new piezoelectric quartz crystal (PQC) sensor using molecularly imprinted polymer (MIP) as sensing material has been developed for fast and onsite determination of pirimicarb in contaminated vegetables. Three MIPs particles have been prepared by conventional bulk polymerization (MIP-B) and precipitation polymerization in either acetonitrile (MIP-P1) or chloroform (MIP-P2). MIP-P2, with uniform spherical shape and mean diameter at about 50 nm, has shown the best performance as the sensing material for PQC sensor. The sensor fabricated with MIP-P2 can achieve a steady-state response within 5 min, a very short response time as compared to MIPs-coated PQC sensor reported in the literature. The sensor developed exhibits good selectivity (low response to those pesticides with similar structures to pirimicarb, such as atrazine, carbaryl, carbofuran and aldicarb) and high sensitivity to pirimicarb with a linear working range from 5.0 × 10−6 to 4.7 × 10−3 mol L−1 (following a regression equation (r = 0.9988) of −ΔF = 0.552 + 1.79 × 106 C), a repeatability (R.S.D., n = 5) of 4.3% and a detection limit (S/N = 3, n = 5) of 5 × 10−7 mol L−1. The MIP-coated PQC sensor developed is shown to provide a sensitive and fast method for onsite determination of pirimicarb in aqueous extract from contaminated vegetables with satisfactory recoveries from 96 to 103% and repeatability (R.S.D., n = 5) from 4.6 to 7.1% at pirimicarb concentrations ranging from 8.0 × 10−6 to 2.0 × 10−4 mol L−1.  相似文献   

3.
The synthesis and performance of a molecularly imprinted polymers (MIPs) as a selective solid phase extraction sorbent for the preconcentration of the carbamate pirimicarb from water samples is described. The MIP was prepared using pirimicarb as the template, methacrylic acid as the functional monomer and ethylene glycol dimethacrylate as the cross-linking monomer, and using chloroform as the solvent. The detection of pirimicarb was carried out by differential pulse voltammetry (DPV) at a hanging mercury drop electrode (HMDE) in 0.1 mol l−1 HCl. Solvents of different polarities were checked for the polymer synthesis, and different experimental variables (sample pH, selection of the eluent used, eluent volume, analyte and eluent flow rates and sample volume) associated with the rebinding/extraction process were optimised. For a 25 ml sample, the process took about 13 min and resulted in a nominal enrichment factor of 50 (eluent MeOH:H2O:HAc, 7:2:1; 0.5 ml) for pirimicarb. A limit of detection of 4.1 μg l−1 was obtained, and a good reproducibility of the measurements using different MIP microcolumns was found. Furthermore, the MIP selectivity was evaluated by checking several substances with similar and different molecular structures to that of pirimicarb. As an application, pirimicarb was determined in water samples of diverse origin which were spiked at a concentration level of 71.5 μg l−1.  相似文献   

4.
The reactions of palladium(II) chloride, PPh3 and heterocyclic-N/NS ligand in a mixture of CH3CN (5 ml) and CH3OH (5 ml) produced [PdCl2(PPh3)(L1)]·(CH3CN) (1) (L1 = ADMT = 3-amino-5,6-dimethyl-1,2,4-triazine), [PdCl2(PPh3)(L2)] (2) (L2 = 3-CNpy = 3-cyanopyridine), [PdCl(PPh3)(L3)]2·(CH3CN) (3), [PdCl(PPh3)2(HL3)]Cl (4) (HL3 = Hmbt = 2-mercaptobenzothiazole). The coordination geometry around the Pd atoms in these complexes is a distorted square plane. In 3, L3 acts as a bidentate ligand, bridging two metal centers, while in 4, HL3 appears as monodentate ligand with one nitrogen donor atom uncoordinated. Complexes 1-4 are characterized by IR, luminescence, NMR and single crystal X-ray diffraction analysis. All complexes exhibit luminescence in solid state at room temperature.  相似文献   

5.
The photodegradation behaviour of ethylene-vinyl acetate copolymer (EVA)/low density polyethylene (LDPE) composite containing four different types of titanium dioxide (TiO2) was investigated through colour difference, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and mechanical tests. The results showed that the performance losses of composites were qualitatively correlated with the degradation degree. The vinyl acetate (VA) groups in EVA were sensitive to UV light and the photodegradation mainly occurred in the amorphous region. The chain scission and annealing effect facilitated the secondary crystallization of composites. The heterogeneous nucleation effect of TiO2 on the crystallization of composites was related to the particle size of TiO2. The micro rutile TiO2, micro anatase TiO2 and their mixture (rutile/anatase = 13/87) exhibited a photo-stabilising effect, while the nano mixed crystals TiO2 (rutile/anatase = 20/80) had an opposite effect.  相似文献   

6.
A simple and efficient synthesis of novel pyrimidine-substituted alkanoate, acetohydrazide, and imines is described. The synthesis of novel ethyl 2-(2,6-dimethylpyrimidin-4-yloxy)acetate (EDMPyA) 2 was performed through SN2 O-alkylation of 2,6-dimethyl-4-hydroxypyrimidine 1 with ethyl haloacetate. The compound EDMPyA 2 was subjected to nucleophilic substitution reaction with hydrazine hydrate to afford novel 2-(2,6-dimethylpyrimidin-4-yloxy)acetohydrazide (DMPyAH) 3. This DMPyAH 3 upon condensation with differently substituted carbonyl compounds (aldehydes/ketones) furnished DMPyAH imines (DMPyAH-I) 4a–d. These imines can be used for the preparation of unique β-lactams. The structure elucidation of all the newly synthesized compounds was performed using spectroscopy (FT-IR, 1H and 13C NMR) and elemental analysis (C, H, N).  相似文献   

7.
A simple, stability-indicating high-performance thin-layer liquid chromatographic (HPTLC) method for analysis of minocycline was developed and validated. The densitometric analysis was carried out at 345 nm using methanol-acetonitrile-isopropyl alcohol-water (5:4:0.5:0.5, v/v/v/v) as mobile phase.The method employed TLC aluminium plates pre-coated with silica gel 60F-254 as the stationary phase. To achieve good result, plates were sprayed with a 10% (w/v) solution of disodium ethylene diaminetetraacetic acid (EDTA), the pH of which was adjusted to 9.0. Compact spots of minocycline were found at Rf = 0.30 ± 0.02. For proposed procedure, linearity (r = 0.9997), limit of detection (3.7 ng spot−1), recovery (99.23-100.16%), and precision (% R.S.D. ≤ 0.364) was found to be satisfactory. The drug undergoes acidic and basic degradation, oxidation and photodegradation. All the peaks of degradation products were well resolved from the pure drug with significantly different Rf values. The acidic and alkaline degradation kinetics of minocycline, evaluated using this method, is found to be of first order.  相似文献   

8.
1,1,4,4-Tetramethylsemicarbazide readily undergoes alkylation with prop-2-ynyl bromide and allyl bromide at the tertiary nitrogen atom of the hydrazine fragment to give 1-(prop-2-yn-1-yl)-and 1-(prop-2-en-1-yl)-1,1-dimethyl-2-(dimethylaminocarbonyl)hydrazinium bromides, respectively. A new procedure was proposed for the synthesis of 6-bromomethylidene-2-dimethylamino-4,4-dimethyl-5,6-dihydro-4H-1,3,4-oxadiazin-4-ium bromide by reaction of 1,1,4,4-tetramethylsemicarbazide with 1,3-dibromoprop-1-yne in acetonitrile.  相似文献   

9.
A reusable optical bioassay platform using permeability-controlled hydrogel pads for selective saccharide detection has been developed. An optical glucose detection assay based on fluorescence resonance energy transfer (FRET) between dye-labeled dextran and Concanavalin A (ConA) was incorporated into hydrogel pads by entrapment. The hydrogel pads are constructed from hemispherical hydrogel attached onto hydrophobic surfaces of a microtiter plate. The resulted hemispherical hydrogel pads entrapping the sensing biological materials were further surface coated with polyelectrolyte multilayers through a Layer-by-Layer (LbL) self-assembly process to create a permeability-controlled membrane with nanometer thickness. The selective permeable LbL film deposited on the hydrogel surface allows small molecular weight analytes to diffuse into the hydrogel pads while the large molecular weight sensing biological molecules are immobilized. An encapsulation efficiency of 75% for the ConA/Dextran complex within the coated hydrogel pads was achieved and no significant leakage of the complex was observed. Glucose calibration curve with linear range from 0 to 10 mM glucose was obtained. Selective permeability of the hydrogel pads has been demonstrated by measurement of saccharides with various molecular weights. The LbL hydrogel pads could selectively detect monosaccharides (glucose, MW = 180) and disaccharides (sucrose, MW = 342) while polysaccharides (dextran, MW ∼ 70 kDa) cannot diffuse through the LbL layer and are excluded. LbL hydrogel pads allow regeneration of the FRET system with good signal reproducibility of more than 90% to construct a reusable and reagentless optical bioassay platform.  相似文献   

10.
A series of Ru(acac)24-diene) complexes containing cis- and trans-diene coordination have been investigated by cyclic voltammetry to correlate structural bonding and conformation patterns of diene ligands with redox behaviors. The solid-state structure of Ru(acac)2(2,3-dimethyl-1,3-butadiene) has been determined by single crystal X-ray diffraction methods. Ru(acac)2(2,3-dimethyl-1,3-butadiene) crystallizes in the monoclinic space group C2/c with a = 12.368(2) Å, b = 17.0600(2) Å, c = 16.0110(2) Å, β = 98.4405(10)° and V = 3341.38(10) Å3 for Z = 8. A structural comparison between several Ru-trans4-diene complexes and Ru-η4-1,3-cyclohexadiene revealed no difference in the Ru-C(diene) bond distances. However, through cyclic voltammetry experiments these species demonstrated different redox behavior, as function of the coordinated diene ligand.  相似文献   

11.
M. Bosco 《Talanta》2007,72(2):800-807
The photodegradation of phenol using TiO2 as catalyst was studied and monitored by fluorescence excitation-emission matrix (EEM). Hydroquinone, catechol and resorcinol were the dihydroxyderivative intermediates although in lower concentrations than phenol. The data were analyzed using a three-way multivariate curve resolution alternating least squares method (MCR-ALS) and augmented matrices. The procedure was assessed using synthetic samples prepared with a {4,3} Simplex-lattice design that considered a representative range of analyte concentrations. The results were analyzed in terms of overall RMSEP for the overall data set. A detailed study was made of how the analytes behaved at each concentration level and how the concentration of the other species affected the process. The method was used to quantify phenol in photodegradation samples with an overall prediction error of 5.37%. The conversion values were fitted to pseudo first-order kinetics and the apparent rate constant was calculated to be −4.9 × 10−4 ± 5.2 × 10−5 min−1.  相似文献   

12.
trans-Di(cyano-κ1)-(trans-6,13-dimethyl-6,13-bis(propionylamido)-1,4,8,11-tetraazacyclotetradecane-κ4)cobalt(III) perchlorate dihydrate, trans-[Co(C18H38N6O2)(CN)2)]ClO4 · 2H2O, is formed by reaction of trans-[Co(diam)(CN)2]ClO4 · 2H2O (diam = trans-6,13-diamino-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane) with propionic anhydride in DMF. The centrosymmetrical cation has the azamacrocycle in planar coordination by the four secondary amine nitrogen atoms of the azamacrocycle, with Co–N = 1.979(2) and 1.968(2) Å and with trans cyano groups with Co–C = 1.920(2) Å. The propionylamido substituents are axially oriented, with the terminal methyl group disordered over two sites.  相似文献   

13.
Azlactone anions—the key intermediates in the classical Erlenmeyer synthesis of amino acids—apparently possess aromatic stabilization, as indicated by the relative rate of base catalyzed deuterium exchange in the following analogs: 1-methyl-2-phenyl-5(4H)-imidazolone > 2-phenyl-5(4H)-oxazolone (azlactone) > 3,3-dimethyl-2-phenyl-4(3H)-pyrrolone. This is paralleled by the relative rate of condensation of these compounds with hexadeuteroacetone. Reported pKa data also suggest that the azlactone products of the Erlenmeyer synthesis are analogs of the fulvenes.  相似文献   

14.
In order to identify the initiation step in the photodegradation of poly(2,6-butylenenaphthalate)-block-poly(tetramethyleneglycol) (PBN-PTMG), we undertook its photolysis with monochromatic irradiation. We discuss the initiation reaction on the basis of the analytical results for the PBN-PTMG in the presence or absence of 2,2′-dihydroxy-4-methoxybenzophenone as a UV absorber, 2-hydroxy-4-methoxybenzophenone as a UV absorber, β-carotene as a quencher of singlet oxygen or methylene blue as a photosensitiser, respectively.The PBN-PTMG containing 2,2′-dihydroxy-4-methoxybenzophenone exhibits better resistance to the incident light of ca. 370 nm corresponding to the absorption of the n, π* transition of the carbonyl group in the PBN block than the PBN-PTMG containing 2-hydroxy-4-methoxybenzophenone. The PBN-PTMG containing β-carotene shows similar photodegradation tendencies as that of the PBN-PTMG without β-carotene. In contrast, the PBN-PTMG with methylene blue is not degraded by monochromatic radiation in the range λ = 600-690 nm. These facts indicate that singlet oxygen does not participate in the initiation reaction of the photodegradation of the PBN-PTMG. Therefore, we concluded that the photodegradation of the PBN-PTMG is induced through the hydrogen abstraction by carbonyl groups in n, π* excited states.  相似文献   

15.
The dinuclear bis(ferrocenecarboxylato) complex Ru2(CO)4(μ-OOCFc)2(py)2 (Fc = ferrocenyl, py = pyridine) was found to react with aromatic diimines (2,2′-dipyridyl, 4,4′-dimethyl-2,2′-dipyridyl, 1,10-phenanthroline, 5-nitro-1,10-phenanthroline, and 5-amino-1,10-phenanthroline) in methanol to give the cationic diruthenium complexes [(N∩N)2Ru2(CO)2(μ-CO)2(μ-OOCFc)]+ (1: N∩N = 2,2′-dipyridyl, 2: N∩N = 4,4′-dimethyl-2,2′-dipyridyl, 3: N∩N = 1,10-phenanthroline, 4: N∩N = 5-nitro-1,10-phenanthroline, 5: N∩N = 5-amino-1,10-phenanthroline), which have been isolated as the hexafluorophosphate salts. The molecular structure of 3, solved by single-crystal X-ray analysis of the tetraphenylborate salt [3][BPh4], shows a diruthenium backbone bridged by two carbonyl and by one ferrocenecarboxylato ligand, the two 1,10-phenanthroline ligands being in the axial positions. Cyclic voltammetry in dichloromethane reveals for all compounds two successive oxidations due to ferrocene/ferrocenium redox couple and oxidation of the diruthenium core.  相似文献   

16.
Ruthenium(II) nitrosyl complexes with polypyrazolylmethanes, [(Bpm)Ru(NO)Cl3] [Bpm = bis(1-pyrazolyl)methane, 1], [(Bpm)Ru(NO)Cl3] [Bpm = bis(3,5-dimethyl-1-pyrazolyl)methane, 2], [(Tpm)Ru(NO)Cl2][PF6] [Tpm = tris(1-pyrazolyl)methane, 3], and [(Tpm)Ru(NO)Cl2][PF6] [Tpm = tris(3,5-dimethyl-1-pyrazolyl)methane, 4], have been synthesized and characterized. The solid-state structures of [(Bpm)Ru(NO)Cl3] (2) and [(Tpm)Ru(NO)Cl2][PF6] (4) were determined by single-crystal X-ray crystallographic analyses. These complexes have been tested as catalysts in the transfer hydrogenation of several ketones under mild conditions.  相似文献   

17.
This work presented a novel method for specific detection of sulfate-reducing bacteria (SRB) based on the photocatalytic property of ZnS nanoparticles. ZnS semiconductor nanoparticles were synthesized by taking advantage of the characteristic bacterial metabolite, sulfide, and then ZnS nanomaterials were used as photocatalyst for methylene blue (MB) photodegradation. As the amount of ZnS photocatalyst synthesized from microbe metabolized sulfide was affected by initial bacterial concentration before cultivation, the photodegradation ratio of MB was highly related with initial SRB concentration. Under the optimized conditions, a linear relationship between the MB photodegradation ratio and the logarithm of SRB concentration was observed in the range of 1.0 × 103–1.0 × 108 cfu mL−1. Besides, this proposed method showed excellent specificity for SRB detection. To the best of our knowledge, this is the first example of using the photocatalytic property of microbial synthesized ZnS for bacterial detection.  相似文献   

18.
Synthesis and Reactions of 8-membered Heterocycles from 3-Dimethylamino-2,2-dimethyl-2H-azirine and Saccharin or Phthalimide 3-Dimethylamino-2,2-dimethyl-2H-azirine ( 1 ) reacts at 0-20° with the NH-acidic compounds saccharin ( 2 ) and phthalimide ( 8 ) to give the 8-membered heterocycles 3-dimethylamino-4,4-dimethyl-5,6-dihydro-4 H-1,2,5-benzothiadiazocin-6-one-1,1-dioxide ( 3a ) and 4-dimethylamino-3,3-dimethyl-1,2,3,6-tetrahydro-2,5-benzodiazocin-1,6-dione ( 9 ), respectively. The structure of 3a has been established by X-ray (chap. 2). A possible mechanism for the formation of 3a and 9 is given in Schemes 1 and 4. Reduction of 3a with sodium borohydride yields the 2-sulfamoylbenzamide derivative 4 (Scheme 2); in methanolic solution 3a undergoes a rearrangement to give the methyl 2-sulfamoyl-benzoate 5 . The mechanism for this reaction as suggested in Scheme 2 involves a ring contraction/ring opening sequence. Again a ring contraction is postulated to explain the formation of the 4H-imidazole derivative 7 during thermolysis of 3a at 180° (Scheme 3). The 2,5-benzodiazocine derivative 9 rearranges in alcoholic solvents to 2-(5′-dimethylamino-4′,4′-dimethyl-4′H-imidazol-2′-yl) benzoates ( 10 , 11 ), in water to the corresponding benzoic acid 12 , and in alcoholic solutions containing dimethylamine or pyrrolidine to the benzamides 13 and 14 , respectively (Scheme 5). The reaction with amines takes place only in very polar solvents like alcohols or formamide, but not in acetonitrile. Possible mechanisms of these rearrangements are given in Scheme 5. Sodium borohydride reduction of 9 in 2-propanol yields 2-(5′-dimethylamino-4′,4′-dimethyl-4′H-imidazol-2′-yl)benzyl alcohol ( 15 , Scheme 6) which is easily converted to the O-acetate 16 . Hydrolysis of 15 with 3N HCl at 50° leads to an imidazolinone derivative 17a or 17b , whereas hydrolysis with 1N NaOH yields a mixture of phthalide ( 18 ) and 2-hydroxymethyl-benzoic acid ( 19 , Scheme 6). The zwitterionic compound 20 (Scheme 7) results from the hydrolysis of the phthalimide-adduct 9 or the esters 11 and 12 . Interestingly, compound 9 is thermally converted to the amide 13 and N-(1′-carbamoyl-1′-methylethyl)phthalimide ( 21 , Scheme 7) whose structure has been established by an independent synthesis starting with phthalic anhydride and 2-amino-isobutyric acid. However, the reaction mechanism is not clear at this stage.  相似文献   

19.
The preparation and characterization of 5,6-substituted-1,10-phenanthrolines, phdtos = 5,6-bistosyl-1,10-phenanthroline (1) and phdbt = 5,6-dibenzyltiol-1,10-phenanthroline (2) are described. The synthesis of (1) was achieved in good yield via the corresponding dihydroxide and 2 was obtained by cross-coupling reaction of 5,6-dibromo-1,10-phenanthroline and benzylthiol mediated by a palladium catalytic system in refluxing toluene (120 °C). These phenanthroline derivatives were used as ligands to afford [FeII(phdtos)3](PF6)2 (5) and [FeII(phdbt)3](PF6)2 (6) complexes.  相似文献   

20.
Today sub-2 μm packed columns are very popular to conduct fast chromatographic separations. The mass-transfer resistance depends on the particle size but some practical limits exist not to reach the theoretically expected plate height and mass-transfer resistance. Another approach applies particles with shortened diffusion path to enhance the efficiency of separations. In this study a systematical evaluation of the possibilities of the separations obtained with 5 cm long narrow bore columns packed with new 2.6 μm shell particles (1.9 μm nonporous core surrounded by a 0.35 μm porous shell, Kinetex™, Core-Shell), packed with other shell-type particles (Ascentis Express™, Fused-Core), totally porous sub-2 μm particles and a 5 cm long narrow bore monolith column is presented. The different commercially available columns were compared by using van Deemter, Knox and kinetic plots. Theoretical Poppe plots were constructed for each column to compare their kinetic performance. Data are presented on polar neutral real-life analytes. Comparison of a low molecular weight compounds (MW = 270–430) and a high molecular weight one (MW ∼ 900) was conducted. This study proves that the Kinetex column packed with 2.6 μm shell particles is worthy of rivaling to sub-2 μm columns and other commercially available shell-type packings (Ascentis Express or Halo), both for small and large molecule separation. The Kinetex column offers a very flat C term. Utilizing this feature, high flow rates can be applied to accomplish very fast separations without significant loss in efficiency.  相似文献   

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