Isao Kojima

Determination of metals in small samples by atomic absorption and emission spectrometry with discrete nebulization

Abstract Eight elements in NBS-SRM 1577 bovine liver and other biological standards are determined by flame atomic absorption (Ca, Cu, Fe, Mg, Mn and Zn) and emission (K and Na) spectrometry. Samples (2 mg) weighed into a 3.8-ml teflon vessel are decomposed with 40 μl of (5 ÷ 1) nitric—perchloric acids in a sealed teflon vessel. A 75-μl or 100-μl aliquot of the diluted sample solution is injected into a small teflon funnel coupled directly to the nebulizer needle of the spectrometer. The results obtained agree well with certified values: the standard deviation is about 2%.

Infrared and X-ray photoelectron spectroscopy studies of carbon monoxide adsorbed on silica-supported cobalt catalysts

The adsorption of CO on silica-supported cobalt catalysts has been studied by means of i.r. and X.p. spectroscopies in order to reveal the nature of Co—CO bonding in connection with the catalytic hydrogenation of CO. For a 7.5 wt% catalyst, a single i.r. band for CO appeared first at ca. 2000 cm–1(band A). With increasing exposure to CO this band shifted to 2040 cm–1, accompanied by a sharp band B at 2180 cm–1. In contrast, a 3.35 wt% catalyst produced only band B. Upon evacuation at room temperature, band B was readily removed, whereas band A, shifting to a lower frequency, remained up to 473 K. X.p.s. has revealed that the surface of the former catalyst has exposed metallic cobalt, whereas the surface of the latter consisted mainly of Co2+ ions even after exposure to H2 at 723 K. Bands A and B were assigned to linearly bonded CO on metallic sites and COδ+ on cationic sites, respectively. An analysis of the variation in frequency of band A as a function of the amount of CO suggested the presence of indirect interaction via the metal electrons. The effect of hydrogen was a shift in band A to lower frequency. This led to the conclusion of weakening of the C—O bond in the presence of H2 and no contribution from COδ+ species to the hydrogenation.

Decomposition of bovine liver in a sealed teflon vessel for determination of metals by atomic absorption spectrometry.

Abstract The teflon-lined bomb described is suitable for acid digestion of biological materials. Total decomposition time with nitric and perchloric acids is 6 h. Blanks are low and results agree well with certified values.

Reaction of vanadium(v) complexes with some adduct-forming substances in benzene

Abstract Vanadium(V) reacts with monobasic and bidentate extracting agents, i.e. 8-quinolinol, 2-methyl-8-quinolinol, salicylaldoxime, hinokitiol, benzoylphenylhydroxylamine, maltol, cupferron, dibenzoylmethane, salicylaldehyde, and phenylmethylbenzoylpyrazolone-5, to form 1:2 complexes containing a basic V=O group and an acidic V—OH group in the same molecule. The basic group reacts with acidic substances to give a hyper- and bathochromic effect; the acidic group reacts with basic substances to give a hyper- and hypsochromic effect. These reactions are observed in benzene solutions.

Monodisperse Metallic Iron Nanoparticles Synthesized from Noncarbonyl Complex

Highly monodisperse, metallic iron nanoparticles were prepared by the alcohol reduction of a nontoxic metal precursor (Fe(III) acetylacetonate) in an organic solvent at elevated temperatures. In order to obtain a metallic iron phase and minimize iron oxide ones, a relatively high molar ratio of the reducing agent to the precursor is required. Compared with a single-step reaction, a two-step seed-mediated synthesis results in the systematic control of particle diameter while maintaining monodispersity. The standard deviation of particle diameter is less than 10%, which is sufficiently small to lead to ordered self-assemblies.

Synergic extraction and photometric determination of vanadium(V) with 8-quinolinol in the presence of phenols

Abstract Vanadium(V) 8-quinolinolate reacts with phenols to form a 1:1 addition compound in organic solvents. Enhanced extraction of vanadium 8-quinolinolate in the presence of phenols can be accounted for in terms of the following reaction: VOOx2OHorg+ArOHorg ⇌ VOOx2OH·ArOHorg.On the basis of the bathochromic effect of phenols and the high molar absorptivity of the complex formed, a sensitive method for the extraction-photometric determination of vanadium has been developed. The analytical results for vanadium in the standard silicate rocks. USGS-BCR-1, USGS-W-l. USGS-PCC-1, USGS-G-2. GSJ-JB-1. and GSJ-JG-1. agreed well with the data reported previously.

Microwave digestion of biological samples with acid mixture in a closed double PTFE vessel for metal determination by “one-drop” flame atomic absorption spectrometry

Abstract A microwave-heat system using a closed double PTFE vessel with a polypropylene jacket was evaluated for rapid sample preparation for the determination of trace elements in biological samples. The microwave-assisted digestion was based on sample dissolution with a HNO 3 HClO 4 HClHF mixture. The simultaneous digestion of six samples including one blank was completed within 15 min even with very mild heating. The presence of an alkaline solution between the PTFE vessels was very effective in aiding the digestion and absorption of evolved acid gases. Six metals (Ca, Cu, Fe, Mg, Mn and Zn) in standard reference materials, NIST-SRM 1577 Bovine Liver, NIES-CRM No. 1 Pepperbush, No. 6 Mussel, No. 5 Human Hair, No. 7 Tea Leaves and No. 9 Sargasso, were analyzed by “one-drop” flame atomic absorption spectrometry. Good agreement of the analytical results with the certified values was obtained.

A simple decomposition and chelating resin separation for the determination of heavy metals in silicates by atomic absorption spectrometry

Abstract A simple method for the determination of copper, nickel, zinc, and cadmium in silicate rock samples is reported. Silicates are decomposed with hydrofluoric acid and aqua regia in a sealed Teflon vessel. After centrifugation and addition of malonic acid, the supernatant liquid is passed through a small column of Chelex 100. The metals are eluted with 2 M nitric acid, and determined by atomic absorption spectrometry. The method is rapid, simple, and free from contamination. The results obtained for 14 standard reference rock samples (USGS, GSJ, and CSRM) agree with literature data; the recovery, reproducibility, and accuracy of the proposed method are satisfactory.

Vapour-phase acid decomposition of highly pure silicas in a sealed PTFE bomb and determination of impurities by “one-drop” atomic spectrometry

Abstract Using a sealed double PTFE vessel with a stainless-steel jacket, the purification of acids used in the vapour phase for the decomposition of highly pure silicas was carried out simultaneously in the same vessel at an elevated temperature. A significant decrease in the metal blank level, even from artificially contaminated acids containing 1 mg of each metal (Al, Ti, Cu, Fe, Mn, Ca, Mg and Na), was observed. By “one-drop” flame atomic absorption and “one-drop” inductively coupled plasma atomic emission spectrometry, Na, Ca, Mg, Cu, Fe, Mn and Ti in silicas were successfully determined owing to the very low blank level. This decomposition method made the determination of trace metals except aluminium in highly pure silicas possible without any other preconcentration step. Aluminium was determined only with the use of a small sample mass, owing to the poor decomposition by acid vapours.

Discrete nebulization in atomic absorption spectrometry with a long absorption tube

Abstract The absolute detection limits obtained with 50 μl of sample solutions for 10 elements in an air—hydrogen flame are listed. The values for silver, cadmium, copper and manganese are of the same order of magnitude as those obtained by graphite furnace atomization. The method was satisfactorily applied to the determination of copper and zinc in Bovine Liver.