Ion chromatography–inductively coupled plasma mass spectrometry determination of arsenic species in marine samples

Arsenic speciation analysis in marine samples was performed using ion chromatography (IC) with inductively coupled plasma mass spectrometry (ICP‐MS) detection. The separation of eight arsenic species, viz. arsenite, monomethyl arsonic acid, dimethylarsinic acid, arsenate, arsenobetaine, tetramethylarsine oxide, arsenocholine and tetramethylarsonium ion was achieved on a Dionex AS4A (weaker anion exchange column) by using a nitric acid pH gradient eluent (pH 3.3 to 1.3). The entire separation was accomplished in 12 min. The detection limits for the eight arsenic species by IC–ICP‐MS were in the range 0.03–1.6 µ g l^?1, based on 3σ of the blank response (n = 6). The repeatability and day‐to‐day reproducibility were calculated to be less than 10% (residual standard deviation) for all eight species. The method was validated by analyzing a certified reference material (DORM‐2, dogfish muscle) and then successfully applied to several marine samples, e.g. oyster, fish muscle, shrimp and marine algae. The low power microwave digestion was employed for the extraction of arsenic from seafood products. Copyright © 2004 John Wiley & Sons, Ltd.     

Solvent and Structural Effects on the Photoreduction of Cobalt(III)-Aryl Amine Complexes in Water–Organic Solvent Media*

Photoreduction of [Co(En)₂Cl(RC₆H₄NH₂)]²⁺ ions (where R = p-OMe, p-OEt, p-Me, m-Me, H, p-F, and m-OMe) in varying compositions of water–methanol and water–1,4-dioxane mixtures containing 15–40% (vol.) of organic co-solvent is carried out. Ultraviolet excitation of the above complexes in air-equilibrated solutions causes bleaching of its intense LMCT excited states with concurrent production of Co²⁺ion. As seen from the quantum yield data, _Co(II) increases smoothly with increasing content of organic co-solvent in the binary mixtures. The observed values indicate that the metal center is reduced by both ligands and solvent. The quantum yield _Co(II) is considerably affected by the substituent R of the amine, RC₆H₄NH₂ ligand. The effects of solvent and substituted ligands on the _Co(II) are estimated quantitatively using linear regression and multiple correlation methods. The former analysis was carried out using Grunwald–Winstein (Y) Gutmann donor number (DN ^N) and Krygowski–Fawcett E ^N _T (solvent empirical parameters). In addition, Kamlet–Taft's , , and * solvatochromic parameters were also used to study the effect of solute–solvent interaction. The effect of substitution on the aromatic amine ligand affects the quantum yield values, which was established using Hammett's substituent constant . Extensive tabulations of percentage contributions of these parameters, calculated using methods reported earlier, provide suitable values which are presumed to explain the quantitative effects of solvent and structural changes in the aromatic ligand on photoreduction of the cobalt(III) complexes.     

Calculating intensities using effective Hamiltonians in terms of Coriolis-adapted normal modes

The calculation of rovibrational transition energies and intensities is often hampered by the fact that vibrational states are strongly coupled by Coriolis terms. Because it invalidates the use of perturbation theory for the purpose of decoupling these states, the coupling makes it difficult to analyze spectra and to extract information from them. One either ignores the problem and hopes that the effect of the coupling is minimal or one is forced to diagonalize effective rovibrational matrices (rather than diagonalizing effective rotational matrices). In this paper we apply a procedure, based on a quantum mechanical canonical transformation for deriving decoupled effective rotational Hamiltonians. In previous papers we have used this technique to compute energy levels. In this paper we show that it can also be applied to determine intensities. The ideas are applied to the ethylene molecule.     

Mass spectral fragmentation pattern of 3-(2′-hydroxyethyl)quinolin-2(1H)-one and its derivatives

Fragmentation patterns resulting from electron impact ionization of 3-(2′-hydroxyethyl)quinolin-2(1H)-one, three of its monosubstituted derivatives and four of its disubstituted derivatives were studied. The molecular ion of quinolinone-2-etbanol undergoes initial fragmentation with the loss of OH^·, H₂O, CO, ^·CHO, CH₂O, CH₂OH^·, CH₂?CHOH and HCNO species. The [M – CHO]⁺ ion is tentatively suggested to have been formed by the expulsion of H^· from the [M – CO]^+· ion and the [M - CHO]⁺ peak may be considered as diagnostic of a 2-quinolone-3-ethanol.     

Self-assembled coordination cage as a reaction vessel: triplet sensitized [2+2] photodimerization of acenaphthylene, and [4+4] photodimerization of 9-anthraldehyde

Inner cavity of Pd-nanocage has been used as a reaction vessel for performing triplet sensitized [2+2] photodimerization of acenaphthylene using water soluble xanthene dyes (Eosin Y and Rose Bengal) as sensitizers, and [4+4] photodimerization of 9-anthraldehyde. Although the [4+4] photodimerization of 9-anthraldehyde gave similar results to solution reaction, the xanthene dye sensitized [2+2] triplet state photodimerization of acenaphthylene encapsulated within Pd-nanocage yielded the syn dimer in quantitative yield. The results obtained from the triplet state [2+2] photodimerization of acenaphthylene within Pd-nanocage is remarkable given the fact that the photodimerization reaction when performed in methanol in the presence of Eosin Y and Rose Bengal gave the syn and anti dimers in the ratio 0.5 and 0.6, respectively. Preaggregation of molecules encapsulated inside Pd-nanocage in a syn fashion seems to be the governing factor for such a behavior.     

Optimization of inoculum to substrate ratio for enhanced methane yield from leather fleshings in a batch study

One of the most significant issues of the last few decades has been tracing for renewable energy sources. Animal fleshing (ANFL) is the most common proteinaceous solid waste accured during the production of leather and it must be disposed of in an environmentally responsible manner. This paper is attempts to assess the biogas production from solid waste originating from the chrome based tannery. Anaerobic digestion of these wastes will be a viable option for waste stabilization and energy production in the form of biogas to be utilized in the industry. The bio-methane potential of the wastes were examined by mixing these wastes with various sources of inoculum and different inoculum to substrate (I/S) ratio considered. The batch experiments were carried out in 2.5 l glass reactors with a various source of inoculumviz., Cow Dung (CD), Elephant Dung (ED) and Bio-Digested Slurry (BDS) with varied inoculum to substrate (LFs) ratios for a retention time of 50 days with replications. The results obtained from the experiments showed that BDS:LF (25:75) had the highest gas production of 14505 ml (651.85 ml CH₄g^?1 VS) followed by CD:LF (50:50) produced 12072.5 ml (789.36 ml CH₄g^?1 VS) and ED:LF (75:25) produced 11252.5 ml (1492.08 ml CH₄g^?1 VS)with a methane content of 63.77, 61.92 and 62.72%, respectively.     

Synthesis of 2-isopropylfuro(2,3-b)quinolines-a new synthesis of (±)-lunacrine, (±)-lunasine and (±)-demethoxylunacrine

A new and convenient synthesis of 2-isopropylfuro-(2,3-b)quinolines ($\text{4}$) from 3-(3-methylbut-1-enyl)-2-quinolones ($\text{2}$) is described. A neat synthesis of the alkaloids (±)-lunacrine ($\text{1a}$), (±)-lunasine ($\text{12a}$) and (±)-demethoxylunacrine ($\text{1b}$) is also reported.     

Synthesis,characterization and electrochemical studies of ruthenium(III) heterocyclic Schiff bases

A series of hexacoordinated Ru^III–PPh₃ complexes of general formula [RuCl(PPh₃)L] (L = tetradentate Schiff bases derived from the condensation of 2-furaldehyde or thiophene-2-carboxyaldehyde with alkyl and aryl diamines have been synthesized. The complexes were characterized by elemental analyses, spectroscopic and cyclic voltammetric studies. All of the complexes were paramagnetic. Coordination of the Schiff base appears to occur through the two nitrogen and two heterocyclic oxygen/sulphur atoms.     

R3Al-R'3SiOTf: novel and powerful reagent system for stereospecific alkylation-silylation reactions of epoxides

[reaction: see text] A novel and powerful reagent system R(3)Al-R'(3)SiOTf for the one-pot alkylation-silylation reaction of epoxides was discovered, and the reactions of various epoxides with the new reagent system have been demonstrated to occur stereospecifically giving rise to the corresponding alkylation-silylation products in excellent yields.     

Recent progress in the improvement of hydrothermal stability of zeolites

Zeolites have been successfully employed in many catalytic reactions of industrial relevance. The severe conditions required in some processes, where high temperatures are frequently combined with the presence of steam, highlight the need of considering the evolution of the catalyst structure during the reaction. This review attempts to summarize the recently developed strategies to improve the hydrothermal framework stability of zeolites.

This review attempts to summarize the recently developed strategies to improve the hydrothermal framework stability of zeolites.