A survey is given on factors and phenomena affecting the electrode response function. Evidences are shown for the predominant role of surface processes in the potential formation reaction.

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Ab-initio and MESQUAC-MO-SCF (Mixed Electrostatic QUAntum Chemical) calculations on LiF structures with various geometries are presented. The LiF oligomers were studied with fixed geometries, corresponding to structures found in the crystal. For these oligomers bond distance optimization was carried out and the corresponding results for their stabilization energy were compared with experimental measurements and results from former calculations, which included geometry optimization. Values for the conversion energy between several geometries of these oligomers are also presented. The MESQUAC-MO-SCF method applied to the solid state gave results close to experimental data. Surface effects on a LiF model crystal (cube with 216atoms with interionic distance 2.01A) are also presented.

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A current scan polarographic and chronopotentiometric examination of transfer processes involving tervalent lanthanides, Ln, and methylene bis (diphenylphosphine oxide), P, in a dichloroethane/aqueous phase pair has resulted in the finding that the ligand diffuses into the aqueous phase and reacts with an Ln(SO₄)⁺ ion to give a singly charged complex Ln(SO₄)P_n⁺, where n is 1 or 2, which then transfers under the influence of the electrical field into the organic phase.

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Two-photon photoionization detection was used to detect 28 polycyclic aromatic hydrocarbons (PAHs) separated by reversed phase liquid chromatography. A windowless flow cell and a nitrogen laser were used to obtain the photoionization signals. The analytical merit of the technique was illustrated by the determination of the limits of detection (LOD) for the 28 PAHs. LODs as low as 50 and 70pg injected were obtained for anthracene and pyrene, respectively. The importance of the chromatographic efficiency is discussed. The dramatic influence of the mobile phase conductivity, which is mainly responsible for the leakage currents, is shown. The lower the leakage current and the solvent polarity, the better the two-photon photoionization detection.

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The determination of trace amounts of bismuth in environmental samples was investigated by hydride generation-atomic absorption spectrometry. For a simpler procedure, an argon-hydrogen flame was used instead of the graphite furnace originally proposed by lee. Under the analytical conditions proposed here, the detection limit was 1ng as bismuth (S/N=2) and the precision was 1.5% (n=7). Analytical results are presented for sediments, seawater, and some standard reference materials.

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A crown ether polymer, poly(dibenzo-18-crown-6) [poly(DB18C6)], efficiently adsorbed iron(III), gold(III), gallium(III), thallium(III) and antimony(V) from hydrochloric acid solutions. The suitable concentrations of hydrochloric acid were ≥8M for iron(III), 0.1-6M for gold(III) and thallium(III), ≥5M for gallium(III) and ≥7M for antimony(V). The extent of adsorption decreased with an increase in concentration of the metals. The capacities of poly(DB18C6) for the metals, except for antimony(V), were 0.9-1.7mmol g^-1. Separations of gold plus thallium, iron and gallium from each other and of gold, thallium or gallium from large amounts of iron were achieved by using the polymer columns.

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The effect of pre-aquation of PtCl₄^2- by Hg(II) ion on the rate of extraction of Pt(II) with acetylacetone in dodecane, as the complex Pt(acac)₂, was investigated at 25°C. Dependences of initial extraction rates on the concentrations of Hg(II) ion, hydrogen ion and acetylacetone suggested that acceleration of the extraction observed in the pre-aquated system is ascribable to the fast reaction between Pt (H₂O)₄²⁺ and acetylacetone in aqueous phase. Heating of aqueous solution of PtCl₄^2- and acetylacetone in Teflon bomb reactor was effective to accelerate the complex formation.

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Solvent extraction of lithium, sodium, potassium and tetrabutylammonium(tba⁺) picrates in aqueous solutions into 4-methyl-2-pentanone(MIBK) was determined at 298K. The absorption spectrum of the MIBK solutions was measured. When the salt concentration was low, the distribution ratio of picrate was constant but it increased by an increase in the concentration. This was explained in terms that the salts were extracted as ion pairs and dissociated nearly completely in the organic phase in the lower concentration range but the dissociation became incomplete as the concentration increased. The extraction as well as the dissociation in the organic phase of the three alkaline picrates were nearly similar to each other. However, the extraction of tba⁺ picrate was much better and the ion pairs dissociated a little more than the alkali picrates. The absorption spectrum of MIBK solutions of tba⁺ picrate was similar to that of its aqueous solutions and the spectrum did not change even in the higher concentration range where a partial association of the ions was assumed from the solvent extraction data. The spectrum of MIBK solutions of alkali metal picrates agreed with that of tba⁺ salt when the concentration was low but the peak shifted to the lower wavelength when the concentration increased. This shift was explained in terms of incomplete dissociation of the ion pairs and the dissociation constants were determined by a dual-wavelength method. The dissociation constants of the alkali picrate ion pairs in MIBK obtained from the spectrophotometric data well agreed with those obtained from the solvent extraction data.

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Several metal chelates of 2-(2-pyridylazo)-5-methylphenol (PAP-5-Me) were extracted from an aqueous phase into a surfactant phase which was separated from a micellar solution of poly(oxyethylene)=4-nonylphenyl=ether with oxyethylene units of 7.5 (PONPE-7.5). On the basis of the distribution curves for the respective chelates, the partition constants of the neutral chelates were determined at 293K at an ionic strength of 0.1 (NaCl). The partition constants were considerably smaller than those expected from the regular solution theory. The partition constants were also dependent upon the kind of metal ions. This fact is probably due to such an ordered structure as liquid crystal in the surfactant phase which can differentiate the size of the metal chelates.

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Adsorption by magnesium oxide of more than forty radionuclides in respective ionic species in water was observed. Generally, the radionuclides in di-valent and/or multi-valent cations are favorably adsorbed by magnesium oxide; but not for the those in mono-valent cations. In addition, the adsorption by magnesium oxide was not effective to most of the radionuclides in negative ionic species. From the observations, the adsorption mechanism is more prominently by the ion exchange of the di- or multi-valent cation species with the hydrous magnesium oxide. Separation of the radionuclides related to the corrosion products possibly produced in a nuclear power plant from natural seawater was attempted by the magnesium oxide adsorption method. It should be emphasized that the adsorption method was found to be practical for separating radionuclides from a large quantity of natural seawater with high recovery and high reproducibility.

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Monensin and salinomycin, which are produced by Streptomyces, are widely used as additives in broiler feed and cattle feed. However, at a certain level, these antibiotics are toxic. For the quality control of feed and premix it is thus very important to monitor the concentrations of these antibiotics. At present, colorimetric methods are widely used for this purpose, but they are rather time-consuming. The present paper describes the application of colorimetric methods to flow injection analysis (FIA) of these antibiotics. The established method facilitates the rapid analysis of feed and premix for the quality checking.

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An automated HPLC method was proposed for the determination of a human epidermal growth factor, hEGF[1-53], and its fragments, hEGF[1-51] and hEGF[1-47], in the cultured medium of E, coli. The cultured medium was directly injected into the HPLC system which was composed of a short protein-coated octadecylsilane (ODS) precolumn for deproteinization and trapping of hEGFs and a usual ODS analytical column. By a column-switching technique, hEGFs trapped in the precolumn were transferred to the analytical column to allow their separation. The detection limits of hEGFs were ca. 100ng by UV detection at 210nm and were ca. 10ng by native fluorescene detection (Ex 287nm, Em 340nm). The recovery of the spiked hEGFs in the present method was almost quantitative (99.5-101.4%) with good reproducibility (less than 3% of RSD, within each run). The present method is simple and reproducible enough for the routine analysis of cultured medium for hEGFs.

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A highly sensitive and specific quantitative assay of the 1β-hydroxylated bile acids and related compounds has been developed by gas chromatography-selected ion monitoring of their methyl ester-trimethylsilyl ether derivatives using the deuterium labeled internal standards: [²H₇] DCA, [²H₇] CA, [²H₅] 3β-hydroxy- and [²H₆] 3β, 12α-dihydroxy-5-cholen-24-oic acids. Calibration curves for these bile acids are useful over the range of 0.01-100μg in serum (0.2 ml), urine (5ml), or lyophilized meconium (1mg). Recoveries of the bile acids and their conjugates ranged from 92 to 101% of the added amounts of their standard samples. In the analysis of bile acids in human meconium by the developed method, novel 1β, 3α, 7α-trihydroxy- (II) and 1β, 3α, 7α, 12α-tetrahydroxy- (IV) 5β-cholan-24-oic acids were determined in significant amounts of 0.24μg/mg (5.3% of the total bile acids) and 0.27μg/mg (6.3%), respectively.

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Flow injection analysis of glucose is described, using a combination of the potentiometric detection with the potential buffer solution consisting of hexacyanoferrate(III)-hexacyanoferrate(II). Effects of the concentration of the potential buffer solution, reaction time and temperature are examined on sensitivity of the proposed analytical method. Glucose from 10^-7M to 10^-3M, for injections of 140μl samples, can be determined by changing concentrations of the buffer solution from 1×10^-5M to 1×10^-2M.

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The applicability of the zone-melting technique using dibenzofuran as a medium to the separation of small amounts of anthracene in polynuclear aromatic chemicals has been studied. After 100mg (or 20mg) of the chemicals containing anthracene had been mixed with 4g of purified dibenzofuran, 20 zone-passes were performed. Most of the compounds and the concomitant impurities could be eliminated from the beginning part of the zone-molten ingot, in which anthracene is concentrated. By this technique, anthracene was separated from chemicals such as pyrene, benz [a] anthracene, 9-fluorenone, and 9, 10-phenanthrenequinone up to 100mg, and perylene and anthraquinone up to 20mg. The zone-molten ingot was cut into halves and the beginning half was dissolved in xylene. Anthracene separated in this half could be determined by synchronous fluorescence spectrometry without removal of dibenzofuran. The recovery of anthracene was 93-95%. The determination limit in the first four chemicals listed was 2ppm and in the latter two the limit was 10ppm.

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A method for sensitive determination of aromatic carboxylic acids in airborne particulates is described. Airborne particulates are collected on silica fiber filters with a high volume air sampler. Aromatic carboxylic acids in the samples are extracted with 0.2mol dm^-3 sodium hydroxide by heating at 70°C. The carboxylic acids are derivatized with pentafluorobenzyl bromide, and cleaned up through a Sep-Pak NH₂ cartridge. The resulting derivatives are determined sensitively and selectively with a gas chromatograph equipped with an electron capture detector. The detection limit is 0.02μg for o-, m- and p- toluic acids, and 0.03μg for benzoic acid.

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