Determination of arsenic by arsine generation with reducing tube followed by graphite furnace atomic absorption spectrometry

Summary A sensitive method for hydride generation and graphite tube furnace atomic absorption spectrometric measurements with a reducing tube has been developed for the determination of arsenic in tea and orchard leaves. Arsines were generated in a horizontal glass tube, in which a pellet of NaBH₄ was placed. 1.5–2.0 l/min of argon flow rate and 2,400° C of atomization temperature were the best experimental conditions. The strong supression of the arsenic signal by Ni and Co was effectively eliminated with 1,10-phenanthroline. A detection limit of 0.3 ng was obtained with a precision of 3–4%.Paper read at the Meeting of the Japan Society for Analytical Chemistry, June 1980     

Preparation of arsenic‐containing white rice grains as calibration standards for X‐ray fluorescence analysis of total arsenic in cereals

A preparation method of arsenic‐containing white rice grains as calibration standards was developed for the X‐ray fluorescence (XRF) analysis of arsenic in rice grains. Calibration standards were prepared by adding 10 g of white rice grains (from Japan) to 100 ml methanol‐containing dimethylarsinic acid corresponding to 2–100 µg arsenic. The mixture was heated, dried at 150 °C, cooled to room temperature, and then stored in a silica gel desiccator. A total of 5.0 g of each calibration standard was packed into a polyethylene cup (32 mm internal diameter and 23 mm height) covered with a 6‐µm‐thick polypropylene film and then analyzed by wavelength‐dispersive XRF spectrometry. The calibration curve for arsenic obtained from the white rice grains containing arsenic showed good linearity over a concentration range of 0.21–5.00 mg kg^?1 arsenic. The limit of detection of arsenic was 0.080 mg kg^?1. To check the reliability of the XRF method, the concentrations of arsenic in six samples of grain cereals and two samples of flour were compared with those obtained by atomic absorption spectrometry after acid decomposition. The values obtained by both analytical methods showed good agreement. Copyright © 2016 John Wiley & Sons, Ltd.     

Light-scattering detection with a fluorimetric detector in high-performance liquid chromatography

Non-fluorescence compounds were detected by a fluorescence detector based on scattering light. The fluorescence detector was used without any modification, and the scattering light was observed at the wavelength twice as long as the excitation wavelength. Actually the wavelength of the observed scattering light was the same as that of the excitation light. The maximum signal was achieved at around 280 nm. The signal was increased with increasing molecular weight or size of analytes. Colloidal silica with nanometer sizes, ethylene glycol oligomers, saccharides and cyclodextrins could be visualized by the present detection method. The detection limit at S/N=3 for colloidal silica with 78 nm was 39 pg for 20-microL injection.     

Reversible redox processes of poly(anilines) in layered semiconductor niobate films under alternate UV-vis light illumination

The synthesis of polyaniline (PANI) with semiconducting layered niobate (NbO) to form PANI/NbO hybrid materials and their reversible color change under a unique redox process under the influence of UV and/or visible light have been investigated. The in-situ polymerization of anilinium chlorides (ANI) packed in a regular orientation in a bilayer structure within the NbO interlayers led to PANI/NbO hybrid powders by heat treatment using (NH(4))(2)S(2)O(8) as the catalyst. The resulting PANI of these hybrids showed the characteristics of a fully oxidized quinoid form, i.e., pernigranine (PG). The PANI/NbO suspension in H(2)O was cast on a glass substrate to form a PANI/NbO film after evaporation of the water with a good parallel orientation of the NbO layers against the glass substrate. Upon UV light irradiation in the presence of a reductant such as MeOH, the violet-colored PANI (PG) polymers within the NbO interlayers were reduced by the NbO-induced photocatalytic reactions and led to a colorless PANI, i.e., leucoemeraldine (LE). Moreover, the resulting colorless PANI/NbO films reverted back to a blue-colored PANI, i.e., emeraldine (EM), due to oxidation by the surrounding O(2) gas. The PANI/NbO hybrid films were able to retain repetitive and reversible photoinduced patterning for over 50 cycles under such alternate UV and visible light irradiation.     

Permeation and separation of benzene/cyclohexane mixtures through liquid-crystalline polymer membranes

The side-chain liquid-crystalline polymer (LCP) was synthesized by the addition of the mesogenic monomer to poly(methylsiloxane) with Pt catalyst. When the benzene/cyclohexane mixtures were permeated through the LCP membranes by pervaporation at various temperatures, the permeation rate increased with increasing benzene concentration in the feed solution and permeation temperature. Though the LCP membranes exhibited a benzene permselectivity, a mechanism of the permeation and separation for the benzene/cyclohexane mixtures was different in the glassy, liquid-crystalline and isotropic state of the LCP membranes. These results suggested that the permselectivity was fairly influenced by the change of the LCP membrane structure, that is, a state transformation. It was found that a balance of the orientation of mesogenic groups and flexibility of siloxane chains is very important for the permeability and selectivity. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys, 35: 699–707, 1997     

Effect of permeation temperature on permeation and separation of a benzene/cyclohexane mixture through liquid-crystalline polymer membranes

When a benzene/cyclohexane mixture of 10 wt % benzene was permeated through side-chain liquid-crystalline polymer (LCP) membranes by pervaporation at various temperatures, the permeation rate increased with increasing permeation temperature. The LCP membranes also exhibited a benzene permselectivity. The permselectivity for the benzene/cyclohexane mixture through the LCP membrane was different in the glassy, liquid-crystalline, and isotropic states. The LCP membrane had different apparent activation energies for permeation at each state. LCP membrane in the liquid-crystalline state had the highest apparent activation energy of the three states. Results suggest that the benzene permselectivity was influenced by changes in the LCP membrane structure, i.e., a state-transformation. It was found that a balance of the orientation of mesogenic groups and the flexibility of the siloxane chains was very important for benzene permselectivity. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36 : 281–288, 1998     

Determination of selenium by hydride generation with reducing tube followed by graphite furnace atomic absorption spectrometry

Summary Selenium was determined in biological samples (tea and bovine liver, NBS, SRM 1577) by a combination of hydride generation with reducing tube, graphite furnace atomization and atomic absorption detection. The selenium was reduced by a pellet of sodium borohydride which was placed in a horizontal glass tube. 1.6–2.0 l/min of argon flow rate and 2400° C of atomization temperature were the best experimental conditions. Copper produces a severe effect on absorbance, even if present in only 2 times the amounts of selenium. Ion-exchange resin (Dowex 50 W-X8) was used for the separation of Cu, Ni and Co. A detection limit of 1 ng was obtained with a precision of 5–6%.

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Selenbestimmung durch Hydriderzeugung im Reduktionsrohr mit nachfolgender Graphitofen-AAS

Zusammenfassung Durch Kombination von Hydriderzeugung und Graphitofen-AAS wurde Selen in biologischen Proben (Tee, Rinderleber, NBS, SRM 1577) bestimmt. Die Reduktion erfolgte durch Natriumborhydrid in einem horizontalen Glasrohr. 1,6–2,0 l/min Argon und 2400° C Atomisierungstemperatur erwiesen sich als optimal. Kupfer übt selbst bei nur doppelter Menge einen störenden Einfluß aus. Zur Abtrennung von Cu, Ni und Co wurde ein Ionenaustauscher (Dowex 50W-X8) verwendet. Die Nachweisgrenze beträgt 1 ng bei einer Reproduzierbarkeit von 5–6%.

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Paper read at the meeting of 9th ICAS/XXII CSI, Tokyo, September 1981     

Effect of solvent extraction on the atomic-absorption spectrophotometric determination of traces of copper with zinc dibenzyldithiocarbamate

Summary The utility of various organic solvents, such as acetates and ketones, for the CuDBC chelate extraction and subsequent atomic absorption spectrophotometric determination is studied. Methyl propionate was found to be the most sensitive solvent. Data for the different substances are presented.

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Einfluß der Lösungsmittelextraktion auf die AAS-Bestimmung von Kupferspuren mit Zinkdibenzyldithiocarbamat

Zusammenfassung Die Verwendbarkeit verschiedener Lösungsmittel (Acetate und Ketone) für die Extraktion des CuDBC-Komplexes und anschließende atomabsorptions-spektralphotometrische Bestimmung wurde systematisch untersucht. Werte für die verschiedenen Substanzen werden angegeben. Die größte Empfindlichkeit kann mit Methylpropionat erzielt werden.

We wish to thank President Dr. Yawara Yoshitoshi and Prof. Dr. Nobuo Sakurai of Hamamatsu University School of Medicine, for their hospitality and encouragement.     

Effects of additional metals on catalyst life of vanadium-containing high silica zeolites in methanol to hydrocarbon conversion

Catalyst life of vanadium-containing high silica zeolites having the ZSM-5 structure was greatly affected by an additional metal incorporated into the crystal. Chromium ion was effective to increase the catalyst life, while zirconium ion decreased it significantly. Temperature-programmed desorption spectra of NH₃ revealed a correlation between the catalyst life and the number of strong acid sites, suggesting that the additional metal affects the catalyst life by changing the number of strong acid sites.

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, ZSM-5, , . , . NH₃ , , , .