Kinetic spectrofluorimetric determination of silver, based on its catalytic effect on the oxidation of pyrocatechol-1-aldehyde 2-pyridylhydrazone by peroxodisulphate in the presence of 1,10-phenanthroline as activator

A kinetic fluorimetric method for the determination of silver is described, based on its catalytic effect on the oxidation of pyrocatechol-1-aldehyde 2-pyridylhydrazone by peroxodisulphate. In aqueous solution silver concentrations of 0.2-0.8 mug ml can be determined, and 10-80 ng ml in the presence of 1,10-phenanthroline as activator. The fluorescent species obtained (lambda(ex) 357 nm, lambda(em) 445 nm) results from oxidation of the reagent. The kinetic parameters and the interferences are reported, and the method is applied to the determination of silver in developed panchromatic plates.     

Extraction-spectrophotometric determination of iron with 2-(2′-benzothiazolylazo)-4,6-dimethylphenol

An extraction-spectrophotometric method for the determination of trace amounts of iron based on its extraction into chloroform with 2-(2-benzothiazolylazo)-4,6-dimethylphenol (BTADMP) from a pH 6.5 medium has been developed. The extracted 12 FeBTADMP complex species allow the determination of 4–30gmg of iron (=3.92×10⁴1·mol^–1·cm^–1 at 790 nm). The method is highly selective and has been applied to the determination of iron in polymineral-polyvitamin pharmaceutical products.     

Engineered pixels using active plasmonic holograms with liquid crystals

Digital holography requires arrays of small reconfigurable elements to achieve complex reconstruction of the hologram with common systems based on pixels utilizing liquid crystal on silicon (LCoS) technology. The backplane of a typical pixel element is potentially underutilized and thus relatively large physical areas exist in which information can be stored and exploited to give additional functionality to pixel elements. Polarisation and wavelength dependent optical properties can be achieved in small areas using the plasmonic effects of optical antennae. The integration of LCs with optical antennae‐based plasmonic holograms allows active modulation of the far field pattern. The work here demonstrates the concept that conventional LCoS pixel elements can be greatly enhanced with the integration of plasmonic holograms, composed of optical antennae patterned on the surface, giving rise to new levels of modulation capability for holographic pixel elements. Using LCs, polarisation dependent effects in plasmonic holograms can be switched. ‘Engineered pixels', with sub‐wavelength multiplexing over both polarisation and wavelength, can increase the channel capacity of a typical LC display device. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Spectrophotometric determination of vanadium with 4-(1′H-1′,2′,4′-Triazolyl-3′-azo)-2-methylresorcinol

Summary 4-(1H-1,2,4-Triazolyl-3-azo)-2-methylresorcinol reacts with vanadium(V) at pH 8.10 (Tris-HClO₄ buffer solution) to produce a pink-violet 11 complex ( _max=525 nm,=2.55×10⁴l·mol^–1· cm^–1) in a 50% (v/v) methanol-water medium, which allows the spectrophotometric determination of 0.1 to 1.51 ppm of vanadium. The method has been applied for the determination of the vanadium content in low alloy steels.

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Spectrophotometriscbe Bestimmung von Vanadin mit 4-(1H-1,2,4-triazo-lyl-3-azo)-2-methylresorcin

Zusammenfassung Vanadin bildet bei pH 8,10 (Tris-HClO₄-buffer) mit 4-(1H-1,2,4-tri-azolyl-3-azo)-2-methylresorcin ein rosenrot-violettes Chelat, dessen Absorptionsmaximum bei 525 nm in Gegenwart von 50% Methylalkohol gemessen wird. Dieser 11-Komplex entspricht bei einer Vanadin-Konzentration von 0,1–1,51g/ml dem Beerschen Gesetz; seine molare Absorptivität ist 2,55×10⁴l·mol^–1·cm^–1. Das Verfahren wurde zur Bestimmung des Vanadins in Stahl verwendet.

     

Pyrocatechol-1-aldehyde salicyloylhydrazone as reagent for the spectrofluorimetric determination of zinc

Summary A procedure is developed for the Spectrofluorimetric determination of 10–800 ppb of zinc with pyrocatechol-1-aldehyde salicyloylhydrazone in a 60% (v/v) ethanol-water medium at apparent pH 6.7 (acetic-acetate buffer). _ex=400 nm, _em=530 nm. Interferences have been evaluated and the method applied to the determination of zinc in alloys and lubricating oils.

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Spektrofluorimetrische Bestimmung von Zink mit Brenzcatechin-1-aldehyd-salizyloylhydrazon

Zusammenfassung Zink bildet mit Brenzcatechin-1-aldehyd-salizyloylhydrazon ein gelbes, fluoreszierendes Chelat in Gegenwart von 60% Ethanol bei pH 6,7 (Essigsäure-Natriumacetat-Puffer); _ex=400 nm, _em=530 nm. Zwischen Intensität der Fluoreszenz und Zink-Konzentration besteht im Bereich von 10 bis 800 ppb Linearität. Das Verfahren wurde zur Bestimmung des Zinks in Legierungen und Schmierölen verwendet.

     

Thermometric titration of mono- and poly-protic acids in water—methanol medium

Several mono- and poly-carboxylic acids are determined in aqueous and methanol—water (50% v/v) media by thermometric titrimetry. The titration errors are evaluated and compared in terms of some structural aspects of the acids tested. Their neutralisation enthalpies are also determined; in most cases the absolute values of these enthalpies decrease as the methanol content of the medium increases.     

Analytical applications of azoisoxazoles. III. Complexes of cobalt,copper, and cadmium with 2-(5′-methyl-2′-isoxazolylazo)-4-methoxyphenol

2-(5′-methyl-2′-isoxazolylazo)-4-Methoxyphenol has been synthesized and its ionization constant (pK_a = 7.98 ± 0.08) spectrophotometrically determined in a 4% ($\text{v}\text{v}$) ethanol-water medium at μ = 0.25 M (NaClO₄). The reagent originates water soluble complexes with cobalt (log β₂ = 11.45 ± 0.16), copper (log β₁ = 7.15 ± 0.10), and cadmium (log β₁ = 3.96 ± 0.12), and can be used for the spectrophotometric determination of cobalt and copper as well as metallochromic indicator for copper.     

Studies on the kinetics of the ligand-substitution reaction of the Zinc(II)-4-(4′-methyl-2-́thiazolylazo)-2-methylresorcinol with 1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid

Spectrophotometric studies have been carried out on the kinetics of the ligand-substitution reaction of the Zinc(II)-4-(4′-methyl-2′-thiazolylazo)-2-methylresorcinol complex with 1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid, in the pH range 8.4–9.4 at μ = 0.25 and 25 °C. The reaction rate constant was established to be $\text{?}\text{(d[}\text{ZnR}{}_2\text{]}\text{dt)}\text{= K[}\text{ZnR}{}_2\text{][H}{}^{\mathrm{+}}\text{][Y′]/[HR}{}^{\mathrm{?}}\text{], and}\text{K = 6.88 × 10}{}^4\text{liter · mol}{}^{\mathrm{?1}}\text{· sec}{}^{\mathrm{?1}}$ was obtained.