Microtitration of Sulfate with Beryllon II as indicator: Determination of sulfate in environmental samples

Summary A new indicator, 2-(8-hydroxy-3,6-disulfo-1-naphthylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid (Beryllon II, DSNADNS) is proposed for microtitrimetric determination of sulfate with barium. This method is an order of magnitude more sensitive (LOD 0.25 ppm) and has less interference than the existing indicators. The color change is sharper and faster compared to Thorin. Titration is carried out in 80% 2-propanol at an apparent pH of 3.5. The superiority of the indicator is attributed to the lower solubility of the bariumdye salt. Results are presented for environmental samples and compared with values obtained by ion chromatography.

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Mikrotitration von Sulfat mit Beryllon II als Indikator: Bestimmung von Sulfat in Umweltproben

Zusammenfassung Als neuer Indikator für die Bestimmung von Sulfat mit Barium wurde 2-(8-Hydroxy-3,6-disulfo-l-naphthylazo)-1,8-dihydroxynaphthalin-3,6-disulfonsäure (Beryllon II, DSNADNS) vorgeschlagen. Das Verfahren ist um eine Größenordnung empfindlicher und wird weniger gestört als bei Verwendung üblicher Indikatoren. Der Farbwechsel ist schärfer und rascher als mit Thorin. Die Titration erfolgt in 80% 2-Propanol bei pH 3,5. Die Überlegenheit des vorgeschlagenen Indikators dürfte der geringeren Löslichkeit seines Bariumsalzes zuzuschreiben sein. Ergebnisse für Umweltproben wurdenmit den Werten der Ionenchromatographie verglichen.

     

Automated determination of total phosphorus in aqueous samples

The determination of total phosphorus in an automated microbatch analyzer system is described. The procedure combines persulfate digestion of the sample and colorimetric detection of orthophosphate by the ascorbic acid reduction of phosphomolybdate in a single processing chamber. Approximately 9 min are required per sample; approximately 1.7 ml of sample and 0.17 ml of total reagent are consumed. The limit of detection is < or =10 microg/1. phosphorus. The method is tolerant of variations in salinity of the sample. Good agreements with ASTM procedures are shown for a variety of test compounds, lake water, wastewater and urine samples.     

Transversely illuminated liquid core waveguide based fluorescence detection Fluorometric flow injection determination of aqueous ammonium/ammonia

The analytical performance of a new type of fluorescence detector, based on a transversely illuminated liquid core waveguide (LCW), has been investigated using the determination of NH(3)/NH(4)(+) as the 1-sulfonatoisoindole. With a very inexpensive combination of a miniature Hg blacklight as an excitation source, a colored plastic sheet as the emission filter, and an integrated blue sensitized photodiode-operational amplifier as the detector (totaling <$100 in hardware cost), we were able to achieve a limit of detection (LOD) of 35 nM (1.6 pmol) NH(3) with a linear dynamic range up to 60 muM NH(3). Details of detector construction and performance are given.     

Efficient White‐Light Generation from Ionically Self‐Assembled Triply‐Fluorescent Organic Nanoparticles

Low cost, simple, and environmentally friendly strategies for white‐light generation which do not require rare‐earth phosphors or other toxic or elementally scare species remain an essentially unmet challenge. Progress in the area of all‐organic approaches is highly sought, single molecular systems remaining a particular challenge. Taking inspiration from the designer nature of ionic‐liquid chemistry, we now introduce a new strategy toward white‐light emission based on the facile generation of nanoparticles comprising three different fluorophores assembled in a well‐defined stoichiometry purely through electrostatic interactions. The building blocks consist of the fluorophores aminopyrene, fluorescein, and rhodamine 6G which represent blue, green, and red‐emitting species, respectively. Spherical nanoparticles 16(±5) nm in size were prepared which display bright white‐light emission with high fluorescence quantum efficiency (26 %) and color coordinate at (0.29, 0.38) which lie in close proximity to pure white light (0.33, 0.33). It is noteworthy that this same fluorophore mixture in free solution yields only blue emission. Density functional theory calculations reveal H‐bond and ground‐state proton transfer mediated absolute non‐parallel orientation of the constituent units which result in frustrated energy transfer, giving rise to emission from the individual centers and concomitant white‐light emission.     

Evaluation of 1st and 2nd generation of poly(amidoamine) dendrimer functionalized carbon nanotubes for the efficient removal of neptunium

Journal of Radioanalytical and Nuclear Chemistry - Herein, sorption of pentavalent neptunium from aqueous acidic solution was carried out onto 1st and 2nd generation of poly(amidoamine) dendrimer...     

Rate equation simulation of temporal characteristics of a pulsed dye laser oscillator

A time-dependent, two-dimensional (in space) rate equation model of a transversely-pumped pulsed dye laser oscillator, which incorporates transverse pump intensity variation in the presence of intracavity dye laser radiation, is proposed to understand and predict its temporal behaviour. The model yields output pulses which agree well with experimental results using rhodamine 6G and kiton red dyes. The shape, amplitude and temporal position of the simulated pulse within the pump pulse vary dramatically across the tuning range of each dye depending on the relative gain and loss values.     

N-Aryl Modification in γ-Lactam: Design and Synthesis of Novel Monocyclic γ-Lactam Derivatives as Inhibitor for Bacterial Propagation

In search of novel γ-lactam antibacterial agents as non-β-lactam mimics of some γ-lactam antibiotics, N-aryl modification in the γ-lactam ring has been made to synthesize compounds 4–8 in two to six steps. Compound 4 was synthesized using the intermolecular Michael addition of diethyl N-(6-coumarinyl)-2-aminomalonate and 3-aryl/(2-heteroaryl)acryloyl chloride followed by intramolecular amidification. Hydrolysis and stereoselective decarboxylation of 4 resulted in the formation of trans- γ-lactam carboxylic acids (5), which on side chain homologation followed by saponification of the intermediate γ-lactam monoester (7) afforded γ-lactam carboxylic derivatives 8. Moderate to good bacterial growth inhibition was observed for some of the synthesized compounds against E. coli and S. aureus.     

Decomposition kinetics ofbis(biguanide)silver(III) cation in acid perchlorate media

Summary In acid perchlorate media, the title complex undergoes intramolecular redox decomposition generating ultimately Ag⁺ ion and oxidation products of the ligand. The reaction follows a simple first-order process, and the observed pseudo-first-order rate constant is given by k_obs=k₀+kK_a/[H⁺] where K_a is the deprotonation constant of the parent complex; pK_a is approximately 5.9 at 30°. The values of 10⁵ k₀(s^–1) and 10⁷ kK_a (Ms^–1) at 30°, I=1.0 M, are 9.3±0.1 and 11.8±1.3; corresponding H (kJ/mol), S (JK^–1 M^–1) values are 105±0.5, 23±1 and 79±8,-96±5, respectively. The results are compared with those for similar reaction of (ethylenebisbiguanide)silver(III) and effect of change in ligand structure on kinetic behaviours of these complexes is discussed.     

Influence of environment and grain size on magnetic properties of nanocrystalline Mn–Zn ferrite

Nanocrystalline Mn_1−xZn_xFe₂O₄ (0.2?x?0.9) was prepared by mechanical alloying of the concerned oxide precursors and subsequent annealing in air and Ar atmosphere, respectively. Milling and annealing in air produces Zn-ferrites (ZnFe₂O₄) instead of Mn–Zn ferrites as MnO converts to higher oxides at higher oxygen partial pressure and fails to dissolve in the spinel phase. This is confirmed by careful quantitative X-ray diffraction analysis using Rietvelt profile matching and also by the non-saturating paramagnetic nature of the magnetization response with very low saturation level of these spinels milled and annealed in air. On the other hand, single-phase Mn–Zn ferrite results from the identical precursor oxide blend when milling and annealing are carried out under controlled (Ar) atmosphere. The average grain size of the as-milled and annealed powders, measured by Rietvelt refinement, varies between 6–8 and 14–18 nm, respectively. Further investigations performed with Mn_0.6Zn_0.4Fe₂O₄ reveal that a careful selection of annealing parameters may lead to an early superparamagnetic relaxation. Therefore, the blocking temperature can be significantly reduced through proper heat treatment schedule to ensure superparamagnetism and negligible hysteresis at low temperature.