Kensaku Haraguchi

Distribution of metal chelates between aqueous and surfactant phases separated from a micellar solution of a nonionic surfactant

A dilute micellar solution of poly(oxyethylene) 4-nonylphenyl ether with oxyethylene units 7.5 (PONPE-7.5) was separated into two phases (aqueous and surfactant phases) at room temperature. The partition constants of several chelating reagents and their metal chelates between the two phases were determined at 293 K and ionic strength 0.1 (NaClO4). The partition constants of the neutral metal chelates depend on the kind of metal ions and were considerably smaller than those expected from the regular solution theory. These facts suggested that the chelates were incorporated into a hydrocarbon environment in the surfactant phase, whereas the chelating reagents were distributed in the poly(oxyethylene) part of PONPE-7.5. A brief review was also presented on the analytical applications to the extraction of metal ions and organic compounds.

Copper(II) binding abilities of molecular weight fractionated humic acids and their mixtures

It was found that the intermolecular interaction between molecular weight fractionated humic acids (HAs) affected the copper(II) binding abilities. The mean values of copper(II) binding constants (μav) and the total binding capacities (Nt) of the molecular weight fractionated HAs were in the range of 6.0–6.6 and 4.7–5.4 (meq g−1 of C), respectively. The μav and Nt values of the unfractionated HA, which could be regarded as a mixture of the fractions, were smaller than those of the fractionated ones (5.6 and 3.8). Moreover, when the fractionated HAs were mixed in the various mixing ratio, the μav and Nt values of all mixtures were not identical to arithmetic mean values of the fractions, but were smaller than those values of the fractions (5.5–5.7 and 2.2–3.6). These results showed the decrease of the copper(II) binding abilities by mixing the fractions. In order to explain these results, the UV-visible absorption, fluorescence, Fourier transform infrared spectra and gel permeation chromatogram of the fractionated HAs and their mixtures were investigated. From the obtained results, we concluded that the decrease of binding abilities in the mixtures was due to the shielding effect of the copper(II)-binding sites by intermolecular interaction between the molecular weight fractions.

Determination of trace elements in sea-water by inductively coupled plasma mass spectrometry after preconcentration by formation of water-soluble complexes and their adsorption onC18-bonded silica gel

A simple and reliable preconcentration method was developed for the determination of seven trace metals (Mn, Fe, Ni, Cu, Zn, Cd and Pb) in sea-water by ICP-MS. The method is based on the formation of water-soluble complexes in an aqueous sample followed by adsorption of the complexes onto a C18-bonded silica gel column. The chelating reagent used was 2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)phenol (5-Br-PAPS). By passage of 100 ml of sea-water sample, after addition of 5-Br-PAPS and adjustment of the pH to 8.3, quantitative adsorption of the metal complexes onto the column took place while the major matrix ions in sea-water passed through the column. A similar but separate sample work-up at pH 4.5 provided acceptably low blank values for Fe. The metals were subsequently eluted with 4.0 ml of 1.0 M HNO3. All seven elements were determined with an all-argon plasma, whereas ultratrace levels of Fe were determined with a nitrogen–argon mixed-gas plasma to reduce the isobaric interference by 40Ar16O on 56Fe. The detection limits of the method, based on a 25-fold preconcentration, range from 0.08 ng l–1 for Cd to 16 ng l–1 for Fe. The precision and accuracy of the method were demonstrated by analyzing coastal and open-ocean sea-water certified reference materials.

Determination of silicon in electrolyte solutions by electrothermal atomic absorption spectrometry using platinum as a chemical modifier

A method has been developed for the determination of silicon by electrothermal atomic absorption spectrometry using platinum as a chemical modifier. The sensitivity for the determination was improved by a factor of 15 in the presence of platinum as compared with that in the absence of a chemical modifier. The calibration curve for silicon was linear over the range 0–0.8 ng, and the detection limit was calculated (as 3σ of the blank absorbance) to be 8 pg. The concentration of silicon in the electrolyte solutions of fuel cells was determined using the platinum modifier and Zeeman-effect background correction, with 0.1 mol l–1 of lithium chloride present as a matrix matching reagent.

Determination of atmospheric trace metal concentrations by isotope dilution inductively coupled plasma mass spectrometry after separation from interfering elements by solvent extraction

An isotope dilution ICP-MS method for the determination of six elements (Ni, Cu, Zn, Cd, Tl and Pb) in atmospheric particulate samples is described. The method involves a complexation/solvent extraction step to separate these elements from potentially interfering elements prior to ICP-MS analysis. Accuracy of the method was demonstrated by analysis of a Vehicle Exhaust Particulates CRM. The method was successfully applied to the analysis of atmospheric particulates collected in a remote mountainous area of Hokkaido Island, Japan.

Chemical structure changes in Cold Lake oil-sand bitumen and catalytic activities during catalytic hydrotreatment

Abstract Chemical structure changes in Cold Lake oil-sand bitumen and catalytic activities of red-mud/sulfur and NiMo catalysts during catalytic hydrotreatment are discussed. Particular attention is given to hydrogenation and hydrogenolysis of structural units, and to the removal of heteroatoms. NiMo catalyst at 450°C reaction temperature gives high conversion of oil-sand bitumen to lower boiling fractions improving H C ratio and extensive removal of heteroatoms. According to the deposition of metals on the spent catalysts, red-mud/sulfur catalyst is effective for bitumen demetallization, removing V and Ni metals.

Activation of serum response factor in the liver of Long-Evans Cinnamon (LEC) rat

We have studied the DNA binding activities of transcription factors in the liver of Long-Evans Cinnamon (LEC) rats, an animal model of Wilsons disease. Owing to a genetic defect, this strain of rats accumulates excessive copper in the liver and develops severe hepatitis and hepatocellular carcinoma. We found that the DNA binding activity of the serum response factor (SRF) was higher in the liver of LEC rats (approximately 2-fold) than in that of Wistar rats. There was a close correlation between the intensity of the activity and the concentrations of copper in the nuclear protein. The DNA binding activity of Sp1, on the other hand, showed similar levels in both LEC and Wistar rats. SRF may play an important role in the development of hepatocellular carcinoma in LEC rats by mediating the proto-oncogene c-fos induction. We suggest that the copper in nuclear protein may be involved in the activation of SRF.

Kinetics of complexation of nickel (II) and copper (II) with some azophenol derivatives in aqueous nonionic surfactant solution

The kinetics of formation of 1∶1 complexes of nickel(II) and copper(II) ions with some azophenol derivatives in aqueous and micellar solution of a nonionic surfactant, Triton X-100, have been studied by a stopped-flow spectrophotometric method. Second order rate constants for the reactions were determined at 298 K and ionic strength 0.1 (NaClO4) in aqueous solution. In the surfactant solution, the pseudo-first-order rate constants for the complexation reactions,k′obs, decreased with increasing the concentration of Triton X-100. This observation was explained by the assumption that the chelating reagents distribute between the micelle of the surfactant and bulk aqueous phase and rate-controlling reactions occur only in the bulk aqueous phase. On the basis of the relation betweenk′obs and the concentration of the surfactant, the partition constants of the reagents between micellar and aqueous phases were determined.

Kinetics of back extraction of some metal 8-quinolinolato chelates with ethylenediamine-N,N,N′,N′-tetraacetate ion

Abstract The kinetics of the back extraction of bis(8-quinolinolato)copper(II)(CuOx 2 ), bis(8-quinolinolato)nickel(II)(NiOx 2 ) and tris(8-quinolinolato)iron(III)(FeOx 3 ) from a chloroform phase to an aqueous ethylenediamine-N,N,N′,N′-tetraacetate ion (EDTA) phase have been studied spectrophotometrically at 25°C and ionic strength of 0.1. In all the systems studied, the rates of back extraction are determined by the reactions in the aqueous phase when agitated at a sufficiently high speed. The rate laws obtained for the three reactions are as follows. − d[CuOx 2 ] d t = {k Cu H [ H + ] + k Cu H 2 Y [ H 2 Y] + k Cu HY [ HY ]}[ Cuox 2 ] − d[NiOx 2 ] d t = {k Ni H 2 Y [ H 2 Y ] + k Ni HY [ HY ]}[ NiOx 2 ] − d[FeOx 3 ] d t = k Fe H [ H + ][ FeOx 3 ] . The rate constants (l. mol −1 s −1 ) were determined as: K H Cu = 3.8 × 10 3 , k H2Y Cu = 2.3 × 10 −2 , k HY Cu = 2.3 × 10 −2 , k H2Y Ni = 5.2 × 10 2 , k HY Ni = 6.5 × 10 and k H Fe = 1.3.

Kinetics and mechanism of back extraction of bis(2-methyl-8-quinolinolato)copper(II) with trans-1,2-cyclohexanediaminetetraacetate ion

The kinetics and mechanism of back extraction of bis(2-methyl-8-quinolinolato)copper(II) (CuL2) from chloroform phase to aqueous trans-1,2-cyclohexanediametetraacetate ion (CyDTA) phase have been studied spectrophotometrically in a pH range between 6·4 and 7·8 at 25°C and ionic strength of 0·1. Within the shaking speed region above 340 strokes/min, the observed rate of back extraction can be regarded as the rate of chemical reaction in the aqueous phase. The reaction proceeds through three reaction paths; the first, a hydrogen ion assisted in the dissociation of CuL2 followed by rapid reaction with CyDTA, the second, a direct H2Y2− attack on the CuL2 and the third, a direct HY3− attack on the CuL2, where H2Y2− and HY3− refer divalent and trivalent CyDTA anions. The rate expression is −d[CuL2]dt = {kH[H+] + kH2Y[H2y2−] + kHY[HY3-]}[CuL2]. The estimated rate constants, kH, kH2Y, and kHY are 1·1 × 104, 2·6 × 10−1 and 1·3 × 10−1 l. mol−1. sec−1, respectively.