Substoichiometric methods are eminently suitable for the determination of many elements. As a new application of substoichiometry, a substoichiometric speciation of the element in different chemical states is proposed. Substoichiometric speciation of As(III) and As(V) is demonstrated as an example. This is based on a highly selective substoichiometric extraction of As(III) with thionalide and As(V) with tetraphenylarsonium chloride in the presence of an excess amount of pyrogallol. Coexistence of other diverse arsenic species including methylarsenic compounds does not give any interference to the selective determination of As(III) and As(V). For substoichiometric radioactivation, a novel application of the synergistic extraction system in a combination of a substoichiometric amount of thenoyltrifluoroacetone with an excess amount of phenanthroline is demonstrated for Yb as an example. Substoichiometric speciation based on the selective speration and an application of synergistic extraction to substoichiometric separation have additional possibilities in substoichiometry.
A new type of synthetic multi-element reference material (SyRM) with pseudo-biological matrix was prepared by a co-polymerization
reaction of an aqueous solution of acrylamide and acrylic acid containing known amounts of the elements. SyRM has the excellent
homogeneity and the quantitative retention of major and trace elements. Elemental composition can simulate the biological
samples to be analyzed. SyRM can be used for the same purpose of conventional certified reference materials with high accuracy
and precision. SyRM was applied as a comparative standard for non-destructive photon and α-particle activation analysis. Selective
preconcentration methods combined with NAA were proposed and the SyRM containing about fifty elements with known amounts was
prepared. In order to evaluate the reliability of present methods, 3d transition elements and rare earth elements were determined
in the SyRM. It was clearly observed that these methods have good accuracy and precision in trace analysis of biological materials
by comparing the analytical results with the original contents in the SyRM. The SyRM supported multielement analysis of marine
macro-algae can be used as comparative standards for the quality assurance of analytical techniques.
The synergic extraction of La(III), Nd(III), Sm(III), Tb(III) and Lu(III) with 0.1M acetylacetone (Hacac) and 1,10-phenanthroline (phen) in benzene was studied. The adduct formation constant,
s, for RE(acac)3 (phen) in benzene was determined. The
s decreases with inceasing atomic number of RE(III). The
s in different organic solvents can be predicted in connection with the activity coefficients of the solutes, and the validity of this prediction is confirmed by good agreement with the experimental values of
s in carbon tetrachloride and heptane.
A redox substoichiometry is proposed for an accurate and precise determination of arsenic. This method is based on the substoichiometric
oxidation of trivalent arsenic to pentavalent with potassium bromate or ceric sulfate followed by the separation of these
species by thionalide extraction of trivalent arsenic. It was applied to neutron activation analysis of arsenic in the NBS
SRM Orchard Leaves and the Shark Powder. The results were obtained with an excellent accuracy and precision.
The combined use of photon activation and γ-γ coincidence spectrometry is described for the useful and selective nondestructive
determination of nickel in geological materials. This method is characterized by the utilization of the nuclide emitting β+ particles in its decay and γ-γ coincidence counting with two gates: one for the annihilation photopeak region and the other
for the higher Compton plateau region. The practical detection limits by this method for nickel, arsenic, rubidium, sodium
and scandium in silicate matrices could be set at 2.0, 1.2, 9.0, 110 and 1.4 μg, respectively.
Partition coefficients of Cu(acac)2 were determined in eleven organic solvents-0.10M perchlorate systems. Their magnitude was compared with that of the enol form of Hacac and evaluated by a modified equation based on the regular solution theory. The partition coefficient of the copper (II) chelate has been demonstrated to strongly depend on some specific solute-solvent interactions such as direct coordination to the central metal and hydrogen bonding to the ligand molecules. In the case of chloroform, particularly the specific interaction has been elucidated by an association reaction, for which the equilibrium constant has been determined.
Recent works on the trace analysis of various materials by activation analysis are summarized. INAA and IPAA are applied for the multielement determination of various standard reference materials and electronic materials. As an example, the analytical results of pepperbush and fluoride glass are shown. In activation analysis using chemical separation, the destructive neutron activation analysis coupled with isotope addition technique is presented and applied to the determination of trace impurities in indium phosphide. Selective substoichiometry and substoichiometric separagtions of some elements are also introduced.
The effect of phenols on the ion-pair extraction of chromium(VI) as chromate anion (HCrO
) with tetraphenylarsonium cation (TPA+) has been investigated. By using TPACl, chromate is extracted as an ion-pair, TPA+·HCrO
, into organic solvents, but its extractability into nonpolar solvents such as carbon tetrachloride is very low. The addition of several phenols greatly enhances the extractability, e.g., the distribution ratio of chromium(VI) between carbon tetrachloride and water rises 5500-fold in the presence of 0.020M 3,5-dichlorophenol in the organic phase. The enhancement was larger when using more acidic phenols and less polar solvents. From the analysis of the extraction data for the 3,5-dichlorophenol-carbon tetrachloride system, it was shown that one molecule of chromate is extracted together with one TPA+ and 1–3 phenol molecules and the extraction constants were determined. The UV spectrum indicated the extracted species including chromate ester to the TPA+·ArOCrO
Mercaptotropone was synthesized from tropone, and its acid dissociation constant (Ka) and distribution coefficient (KD) between benze and aqueous solution were spectrophotometrically determined as 5.75 (pKa) and 2.46 (log KD); Extraction behaviour of Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Pb(II), Cr(III), Fe(III), Y(III), and Zr(IV) with this reagent into benzene was examined. Cu(II) and Fe(III) were completely extracted from acidic solution, Mn(II), Co(II), Ni(II), Zn(II), Pb(II), and Zr(IV) were also extracted from intermediate pH region, a part of Cr(III) was extracted, but Y(III) was not extracted.