Tooru Kuwamoto

Chemical speciation of chromium in sea water: Part 2. Effects of Manganese Oxides and Reducible Organic Materials on the Redox Processes of Chromium

Abstract Experiments designed to clarify the role of manganese oxides in the oxidation process of Cr(III) to Cr(VI) in sea water are described. The theoretical redox equilibrium controlled only by dissolved oxygen is shown not to be always attained for the Cr(III)/ Cr(VI) system in practice. Some naturally occurring materials can reduce Cr(VI) under the conditions of natural sea water.

Chemical speciation of chromium in sea water: Part 1. Effect of Naturally Occurring Organic Materials on the Complex Formation of Chromium(III)

Abstract The effect of naturally occurring organic materials on the coprecipitation behaviour of trivalent chromium is studied to estimate the relative abundance of organic-bound chromium in sea water. Some amino acids and polyhydric organic acids can bind chromium(III) under the conditions prevalent in natural sea water. Some of the chromium(III) in sea water therefore probably occurs in organic species.

Chemical speciation of chromium in sea water: Part 3. The determination of chromium species

Abstract A method for the determination of chromium(III), chromium(VI) and organicallybound chromium in sea water is reported. It is confirmed that sea water contains about 9 × 10 -9 M dissolved chromium. This is shown to be divided as ca. 15% inorganic Cr(III), ca. 25% inorganic Cr(VI) and ca. 60% organically-bound chromium. It is suggested that the inconsistency of earlier results on the dominant chromium species and its concentration in sea water is largely due to the fact that organically bound chromium species were not considered.

Tungsten in North pacific waters

Tungsten in oceanic waters has only been analysed in a few coastal areas. Here, we report the first tungsten depth profiles in oceanic waters. Tungsten concentration in the north Pacific is constant at 53–60 pmol l−1 (normalized to a salinity of 35‰) from the surface to the bottom. Similar vertical profiles of tungsten and molybdenum probably result from the fact that both elements are hardly adsorbed at all onto organisms and particulate organic matter in surface waters. However, although the crustal abundance of tungsten and molybdenum are nearly equal, the concentration of tungsten is ∼ 11800 of that of molybdenum in oceanic waters. This indicates that tungsten is removed from seawater much more rapidly than molybdenum, by adsorption onto ferric hydroxide, manganese oxide and clay minerals.

Ion chromatographic elution behaviour and prediction of the retention of inorganic monovalent anions using a phosphate eluent

Abstract For the prediction of the retention times of inorganic anions with a phosphate eluent, Jenkes model was modified by using the elution system coefficients as a new concept instead of the calculated selectivity coefficients and measured effective column capacity as in Jenkes method. The capacity factors of analytes were precisely determined by using the modified calculation equation over a wide range of pH.

Gas chromatography of metal chelates with carrier gas containing ligand vapour.

Abstract The vapour of the ligand was used as carrier-gas additive in the gas chromatography of metal chelates. The effect of trifluoro-acetylacetone on non-symmetrical peaks was examined for Be(TFA) 2 , Al(TPA) 3 Cr(TFA) 3 , Pe(TFA) 3 , U(TFA) 4 and Th(TFA) 4 . All the chromatograms appeared quite normally especially those of Th(TFA) 4 ; Fe(TFA) 3 and Th(TFA) 4 were improved markedly by using the carrier gas containing ligand vapour.

Determination of germanium by graphite-furnace atomic-absorption spectrometry

The premature loss of germanium as volatile GeO results in low sensitivity and poor reproducibility in the determination of germanium by graphite-furnace atomic-absorption spectrometry. This interference can be eliminated by suppressing the premature reduction of GeO(2) to GeO during the ashing step, and dissociating the germanium oxides into the atoms simultaneously with their vaporization during the atomization step. The premature reduction of GeO(2) to GeO has been successfully prevented by several approaches: (1) diminishing the reducing activity of the graphite furnace by (a) oxidizing the graphite surface and intercalating oxygen into the graphite lattice with oxidizing acids, such as nitric or perchloric, in the sample solution, or (b) using a tantalum-treated graphite furnace; (2) keeping the analyte as germanium (IV) by addition of sodium or potassium hydroxide to the sample solutions.

Fundamental investigation of thermal properties of rare-earth β-diketonates

Abstract The thermal properties of the rare-earth chelates of Htfa (trifluoroacetylacetone) and Hhfa (hexafluoroacetylacetone) have been investigated. Thermogravimetric curves were obtained by heating samples in the injection chamber of a gas chromatograph, both in an atmosphere of helium, and of helium containing ligand vapour. None of the chelates was completely vaporized in a helium atmosphere at temperatures up to about 240°, but the tfa chelate of Lu and all the hfa chelates were completely vaporized in the atmosphere of helium containing ligand vapour. The vapour pressures and heats of vaporization of these chelates were also measured.

Gas chromatography of metal chelates with carrier gas containing ligand vapour : Thorium(iv) trifluoroacetylacetonate

The vapour of the ligand was used as carrier-gas additive in the gas chromatography of metal chelates. The effect of trifluoro-acetylacetone on non-symmetrical peaks was examined for Be(TFA)(2), Al(TPA)(3) Cr(TFA)(3), Pe(TFA)(3), U(TFA)(4) and Th(TFA)(4). All the chromatograms appeared quite normally especially those of Th(TFA)(4); Fe(TFA)(3) and Th(TFA)(4) were improved markedly by using the carrier gas containing ligand vapour.

Sensitivity of non-suppressed ion chromatography using divalent organic acids as eluents

Abstract Aqueous organic acids such as tartaric and malic acids were effective as eluents for some rapidly eluted anions in non-suppressed ion chromatography. For these eluents, the equation for the sensitivity was derived and the response of the conductivity detector was calculated. Reasonable agreement was found between the observed and calculated sensitivities.