Search results for "Azine"
showing 10 items of 1589 documents
2,2′-Bipyrimidine- and 2,3-bis(2-pyridyl)pyrazine-containing manganese(II) compounds: Structural and magnetic properties
2003
The preparation, crystal structures and magnetic properties of four different manganese(II) compounds of formula [Mn(bipym)Cl2]n·2nH2O (1), [Mn2(dpp)2(H2O)2Cl4]·2H2O (2), [Mn(dpp)(H2O)2]n(ClO4)2n·1.5nH2O (3) and [Mn(dpp)(dca)2]n (4) [bipym = 2,2′-bipyrimidine, dpp = 2,3-bis(2-pyridyl)pyrazine and dca = dicyanamide anion] are reported. Compounds 1 and 3 are uniform chains of six-coordinated manganese(II) ions bridged by bis(bidentate) bipym (1) and dpp (3) ligands with two chloride groups (1) and two water molecules (3) in cis position. The electroneutrality in 3 is achieved by uncoordinated perchlorate anions. The manganese atom in 1 and 3 exhibits a distorted octahedral environment mainly …
Synthesis, X‐ray Crystal Structure and Magnetic Properties of Oxalato‐Bridged Copper( II ) Complexes with 2,3‐Bis(2‐pyridyl)pyrazine, 2,3‐Bis(2‐pyrid…
2004
Five oxalate-containing copper(II) complexes of formula [Cu(dpq)(H2O)(ox)]·5H2O (1), [Cu(dpp)(H2O)(ox)]·H2O (2), [Cu(bpz)(ox)]n (3), [Cu2(dpp)2(H2O)2(NO3)2(ox)]·4H2O (4) and [Cu2Cl2(bpz)2(H2O)2(ox)][Cu(bpz)(H2O)2(ox)]·2H2O (5) [dpq = 2,3-bis(2-pyridyl)quinoxaline; dpp = 2,3-bis(2-pyridyl)pyrazine; bpz = 2,2′-bipyrazine; ox = oxalate] were prepared and their structures were determined by X-ray diffraction on single crystals. Complexes 1 and 2 are discrete mononuclear complexes with oxalate and dpq (1)/dpp (2) acting as bidentate ligands. Complex 3 is a neutral oxalato-bridged (2,2′-bipyrazine)copper(II) chain where the oxalate adopts a bidentate/monodentate coordination mode, whereas 4 is an…
Advantages of monolithic over particulate columns for multiresidue analysis of organic pollutants by in-tube solid-phase microextraction coupled to c…
2011
Abstract The performance of a monolithic C 18 column (150 mm × 0.2 mm i.d.) for multiresidue organic pollutants analysis by in-tube solid-phase microextraction (IT-SPME)-capillary liquid chromatography has been studied, and the results have been compared with those obtained using a particulate C 18 column (150 mm × 0.5 mm i.d., 5 μm). Chromatographic separation has been carried out under isocratic elution conditions, and for detection and identification of the analytes a UV-diode array detector has been employed. Several compounds of different chemical structure and hydrophobicity have been used as model compounds: simazine, atrazine and terbutylazine (triazines), chlorfenvinphos and chlorp…
Determination of cyromazine in pesticide commercial formulations by vibrational spectrometric procedures
2004
Two vibrational spectrometry-based methodologies were developed for Cyromazine determination in solid pesticide formulations: a Fourier transform infrared (FTIR) procedure, based on the extraction of Cyromazine by CH3OH and direct determination in the extracts by peak height measurement at 1622 cm−1 corrected using a baseline defined at 1900 cm−1, and a FT-Raman determination, made directly on the powdered solid products using standard chromatographic glass vials as sample cells and measuring the Raman intensity between 633 and 623 cm−1 for a baseline established between 663 and 601 cm−1. The sensitivity obtained was 0.01631 absorbance g−1 mg for FTIR determination and 2.23 area values g−1 …
Changes in yield ofin-vivo fluorescence of chlorophyll a as a tool for selective herbicide monitoring
1993
Triazines and derivatives of phenylurea, which are often found in outdoor water samples, induce specific changes in the yield of thein-vivo chlorophyll α-fluorescence of PSII. These changes are correlated quantitatively with the concentration of the herbicides and can therefore be used to set-up a low-price monitor system. In order to detect selectively the herbicide-sensitive part of the fluorescence emission a pulse amplitude modulated fluorimeter was used. The bioassay system was optimised with respect to test organism, growing and measuring conditions. The relationship between fluorescence yield and herbicide concentrations were experimentally determined for the triazines atrazine and s…
Determination of pesticides in soil samples by solid phase extraction disks
1993
A systematic study comparing the methodology and analytical results obtained in an investigation of seven pesticide residues (Molinate, Atrazine, Carbofuran, Pirimicarb, Prometryn, Malathion and Tetrachlorvinphos) in soil samples is reported. Solid-phase extraction (SPE) using glass columns and 47 mm disks of octyl and octadecyl-bonded silica was used in the pesticide analysis. The best extraction efficiency and clearest extracts are obtained with C8 disks. The analyses were carried out by capillary gas chromatography with nitrogen and phosphorus detection. Recovery experiments were performed at ppb levels in spiked soil samples. The average recoveries of the compounds were 53–77%. Detectio…
FTIR determination of Aspartame and Acesulfame-K in tabletop sweeteners.
2004
Two different strategies for sweeteners determination in tabletop samples by Fourier transform middle-infrared (FTIR) spectrometry, an off-line and a fully mechanized extraction of Aspartame and Acesulfame-K with different mixtures of chloroform and methanol, have been developed. The off-line method involves the extraction of both active principles by sonication of samples with 25:75 v/v CHCl3/CH3OH and direct measurement of the peak height values at 1751 cm(-1), corrected using a baseline defined at 1850 cm(-1) for Aspartame, and measurement of the peak height at 1170 cm(-1) in the first-order derivative spectra, corrected by using a horizontal baseline established at 1850 cm(-1), for Aces…
Micropumping multicommutation turbidimetric analysis of waters
2007
Abstract A micropumping multicommutation manifold to perform turbidity determinations in waters is described. The procedure is based on the use of a combination of hydrazine sulfate and hexamethylenetetramine, to obtain an external standard of nephelometric turbidity units (NTU), which could compare the absorbance measurements at high wavelengths for samples with a calibration line obtained from a concentrated formazine standard diluted on-line. To minimize sample and reagent consumption and waste generation, the flow system was designed with two solenoid micro-pumps, one of them for the alternative introduction of the formazine standard and samples and the other one for the water carrier. …
Determination of carbonyl compounds in particulate matter PM2.5 by in-tube solid-phase microextraction coupled to capillary liquid chromatography/mas…
2013
Abstract In this paper, a new procedure based on in-tube solid phase microextraction (IT-SPME)-capillary liquid chromatography hyphenated to mass spectrometry detection by using microelectrospray ionisation (CapLC–MS), has been reported. The device was proposed to quantify 12 carbonyl compounds (10 aliphatic aldehydes, an unsaturated aldehyde and a ketone) derivatized with 2,4-dinitrophenylhidrazine (DNPH) reagent in aqueous extracts of PM 2.5 . This methodology involves the on-line preconcentration of DNPH-carbonyl compounds derivatives coupled to the CapLC–MS system, efficiently providing appropriate sensitivity for the determination of the target analytes. Detection limits for the analyt…
Separation of plasma membrane proteins of cultured human fibroblasts by affinity chromatography on bonded microparticulate silicas.
1984
Abstract Adsorbents for high-performance affinity chromatography were prepared by bonding proteins and reactive Procion triazine dyes to 3-isothiocyanatopropyl- and 3-aminopropylsilicas. The materials prepared were used successfully in the separation of hydrophobic plasma membrane proteins of cultured human fibroblasts. The data obtained show that the reaction of 3-isothiocyanatopropyltriethoxysilane (ITCPS) with the surface hydroxyl groups of silica yields a new and convenient route to preparing an “activated carrier” that is capable of coupling with potential affinity ligands containing amino functional groups. The reaction and bonding procedures of 3-isothiocyanatopropyltriethoxysilane a…