Two subjects are reviewed concerning the electrochemical approach to ion solvations. In Section 2, applications of ion-selective electrodes as sensors for ion solvations are discussed. In Section 3, the problem of the liquid junction potential between different solvents is discussed in connection with the difficulties encountered in the study of ion solvations.

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The flow rate ν and column length L are simultaneously optimized in liquid chromatography with the aid of the information measure, FUMI Φ, and its related functions: the information flow υ and information loss δΦ. Two types of the optimal conditions are selected for the liquid-chromatographic analysis of an antipyretics mixture. For the most precise analysis (Φ-optimal), the shortest possible column and a low flow rate ν are recommended. A slightly longer column than the Φ-optimal L and a higher υ are recommended for the most efficient (rapid) analysis (υ-optimal). Both the Φ- and υ-optimals avoid strong peak overlap. The above-mentioned operational difference of the optimals is obtained by the computer simulation of chromatograms of the antipyretics.

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Measurement of the activity of a lipase-detergent complex in a homogeneous system using 4-methylumbelliferyl oleate as a fluorescent substrate was studied. A linear relation between the quantity of the complex and the amounts of 4-methylumbelliferone formed was obtained up to 240pmol/tube when incubated with 0.05mM 4-methylumbelliferyl oleate in aqueous 95% tetrahydrofuran. Under these conditions, the activity of the complex is about 1pmol min^-1 μg^-1. The maximum activity was obtained in neutral or weakly alkaline medium. In this assay system, metal ions such as Fe³⁺ and Co²⁺ strongly inhibited the activity. This method could be applied to the screening of lipase inhibitors in foods.

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The sensitivity of combined headspace gas chromatography (HSGC) and mass spectrometry (MS) for a stimulant (methamphetamine) and its urinary metabolite (amphetamine) was investigated. The analytical methods consisted of a combination of (1) HSGC and electron impact (EI)-MS, (2) HSGC, on-column trifluoroacetyl (TFA) derivatization of stimulants and EI-MS and (3) HSGC and chemical ionization (CI)-MS using isobutane as a reagent gas. The combination of HSGC and EI-MS after on-line TFA-derivatization of stimulants (2) was the most informative method in these three procedure, but HSGC/CI-MS (3) was the most sensitive method. Detection limits of methamphetamine (MA) and amphetamine (AP) in urine by HSGC/CI-MS were found to be about 10ng/ml (S/N>10) by monitoring quasimolecular ions of these compounds; m/z 150 and 136 observed on their mass spectra, respectively. Furthermore, the most sensitive CI-MS method was applied to quantivative analysis of these drugs excreted in urine by the selected ion monitoring (HSGC/CI-SIM).

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A new analytical method for a herbicide, methyl 3-[1-(allyloxyimino)butyl]-4-hydroxy-6, 6-dimethyl-2-oxocyclohex-3- enecarboxylate, sodium salt (alloxydim-sodium), in ground water is described in this report. By this method, the total content of alloxydim-sodium and its degradation products found in soil can be analyzed. Alloxydim-sodium and its degradation products from ground water were converted to 2-methoxycarbonyl-3, 3-dimethylpentane-1, 5-dioic acid and 3, 3-dimethylpentane-1, 5-dioic acid by oxidation with hydrogen peroxide under reflux. After excess hydrogen peroxide was decomposed, the products were extracted with ethyl acetate under acidic condition. After the extract was dried up, the residue was methylated with diazomethane. These derivatives were determined using a gas chromatograph mass spectrometer (GC-MS) before and after a cleanup procedure by Sep-pak Florisil ® The detectable limit was 0.1ppb (μg/l) for each compound. The recovery of alloxydim-sodium and its degradation products ranged from 53 to 85%.

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Protein-coated cyanopropyl silica gel packed in a precolumn was successfully used as an adsorbent for ketoprofen in blood plasma. After column switching, ketoprofen collected in the precolumn was transferred into an ovomucoid column, and the chiral separation was carried out by a mobile phase of 0.1 M phosphate solution (pH 3.2) containing 20% methanol. The separation factor was 1.32, and the resolution was 1.30. The recovery by direct injection of plasma samples was approximately 100%, with a relative standard deviation of about 5% between days (n=6). The calibration graph of each enantiomer was a straight line up to 1nmol; each detection limit was 5pmol (S/N=5).

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A method has been developed for the enantioselective determination of the title compound S-145, a novel thromboxane A₂ receptor antagonist, in a plasma by competitive radioimmunoassay. In order to obtain an antiserum that is optically specific to (+)-S-145 or (-)-S-145, hapten-carrier conjugates were individually prepared by coupling with bovine serum albumin. In displacement studies with enantiomerically pure radioligands, the opposite enantiomer showed a negligible cross-reaction (0.1 to 0.3%) and the racemate showed about a 50% cross-reaction. No cross- reactivity was found with related prostanoids, except for a few metabolites of S-145. The minimum detectable dose (p<0.05) of radioimmunoassays for each enantiomer of 5-145 was 0.5pg/tube. By applying these radioimmunoassays to plasma samples, we developed a precise assay technique without using prior extraction. The limit of the determination of both enantiomers was 200pg/ml in human plasma. The recovery was almost 100%. The intra- and inter-assay variances were 6-12% and 4-10% for human plasma, respectively. When the plasma levels were determined for each enantiomer after an oral administration of the S-145 racemate to several animal species, significant differences were observed between the two enantiomers.

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A sensitive and selective method based on the formation of ternary complexes of berberine, quinidine and a divalent anion of dibasic acid dyes (A^2-) such as Bromophenol Blue, Bromochlorophenol Blue and Bromocresol Green is described. Berberine was extracted in large amounts into 1, 2-dichloroethane with A^2-; only in the presence of quinidine in a neutral aqueous media. Berberine could react in 1, 2-dichloroethane with A^2- to give a blue product. In addition, the extractability of Berberine in a neutral aqueous media could be enhanced by the formation of bulky ternary complexes (berberine⁺-A^2--quinidine⁺); the selectivity was improved because most of the amines and alkaloids did not react with A^2- in the above-mentioned media. The blue complexes can be used for a sensitive and selective spectrophotometric determination of berberine in crude drugs.

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Two pairs of cinchona alkaloids, quinine/quinidine and cinchonine/cinchonidine, were extracted by ion-pair formation with some anions of camphor derivatives. The extraction behaviors are examined, and the differences between the two isomers compared. These alkaloids were extracted into chloroform and 1, 2-dichloroethane in the pH range 4-7 as a 1:1 ion-pair with chiral anions. The relationship between the distribution ratio of the ion-pair and pH is discussed. In the pH range between the pK_a1, and pK_a2 values of cinchona alkaloids, the extraction constants were determined, and the differences caused by the effect of substituents of cinchona alkaloids and counter ions were examined. The solvent effect were also studied.

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The dual-mode nebulization system in inductively coupled plasma atomic emission spectrometry was newly designed for practical use, using a small spray chamber and a concentric nebulizer. The drain in the one-way mode was simply switched to the nebulizer with a rotary valve for the recycling mode. The present system allowed nebulization to maintain for 20min with a 2ml sample, a rapid sample exchange within 10 min, and a low memory of 0.01%. A problem due to the gradual enrichment of determinants was easily overcome with an internal standard method. The sensitivity and reproducibility in both modes were comparable to those of a conventional one-way system. The present system was successfully applied to the analysis of some reference materials. A decomposed sample was measured in the recycling mode, while standards for calibration were measured in the one-way mode in order to save time and procedure.

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A method for the continuous introduction of volatile hydrides and mercury into a helium microwave-induced plasma using a hydrogen separation membrane has been developed. Upon passing the evolved gaseous species through a hollow-fiber membrane, hydrogen and water vapor were removed, while the hydrides and mercury were left and introduced into the plasma. The detection capabilities of a tangential flow torch and two capillary discharge tube torches were compared. The effects of the carrier and auxiliary gas flow rates, hydrogen separation temperature and volume of buffer tank were investigated for germanium. The detection limits for Ge, As, Sb, Sn and Hg were 0.04, 0.32, 6.1, 1.4 and 0.50ng/ml, respectively. The relative standard deviation of the emission intensities of Ge at 5ng/ml was 1.4% (n=7).

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Laser-induced plasmas generated by a Q-switched Nd: YAG laser were observed with an optical imaging spectrometer which was assembled from a 0.32m spectrometer and a cooled CCD (charge-coupled device) detector. The ambient atmosphere, the kind of gas used and its pressure, influenced the emission intensities for both atomic lines and the continuum, and the volume of emissive regions of plasmas. The power density of the laser also affected the plasma characteristics. Tight focusing of laser radiation did not directly bring about a plasma of high emission intensity, because of the absorption of laser energy by the plasma itself. The importance of prevention of a gas breakdown before sample vaporization was also indicated. These effects are discussed from the viewpoints of initial cascade growth of electron number density, absorption of laser energy by the plasmas, and plasma expansion processes.

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Nanogram quantities of copper(II), chromium(III) and manganese(II) in a 100-ml water sample were quantitatively coprecipitated with indium hydroxide at pH 9.5. The precipitate was centrifuged and dissolved in 0.5M hydrobromic acid. The desired heavy metals in the solution (5ml) were directly determined by graphite-furnace atomic absorption spectrometry, where the indium was nearly completely removed by volatilization as bromide at the ashing step. Though no loss of the analytes mentioned above was observed, cadmium and lead were significantly lost during the ashing stage. The time required for the coprecipitation and determination was about 30min.

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A rapid and accurate method for the simultaneous determination of aluminum(III), iron(III) and beryllium(III) is proposed. The method can be applied to the determination of aluminum(III), iron(III) and beryllium(III) in rainwater without any preliminary separation. The determinations are performed by a CPA matrix method with spectrophotometric detection using Chromazurol S. The results obtained in analyses of rainwater samples are reported in order to demonstrate the effectiveness of the proposed method.

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N, N′-Diphenylpropanedithioamide (DPDTA) forms a stable 1:2 (metal:ligand) complex with palladium(II), which is quantitatively extracted from aqueous solutions of pH 1.5-5.8 into toluene, the extract having an absorption maximum at 357nm. Beer′s law is obeyed over the range 0.1-2.0μg ml^-1 of palladium. The apparent molar absorptivity is 4.76×10⁴M^-1 cm^-1. A sensitive and selective extraction-spectrophotometric method for the determination of micro amounts of palladium has been proposed. Further, the equilibria and kinetics of the extraction of palladium(II) with toluene solutions of DPDTA have been studied. The partition coefficient of DPDTA and the extraction constant of its palladium(II) complex between an aqueous and a toluene phase were determined to be 10^{3, 13} and 10^7.56, respectively. The reaction orders of the rate of the complexation reaction of palladium(II) with DPDTA in the extraction were +1, 0 and +1 with respect to the concentrations of palladium(II), hydrogen ion and DPDTA, respectively. Kinetic data and activation parameters for the reaction have also been determined.

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Thiosulfate was oxidized stoichiometrically to sulfate with Iodate in a sulfuric acid medium. The produced iodine, equivalent to the excess iodate, was spectrophotometrically measured as triiodide at 350nm. The complete oxidation of thiosulfate to sulfate using iodate was achieved. The reaction rate was investigated in a medium containing varying amounts of sulfuric acid at room temperature and at 40°C. A linear calibration graph with a negative slope was obtained over the concentration range 4×10^-7-4.3×10^-5M (mol dm^-3)(0.045-4.82ppm) thiosulfate. The relative standard deviation was 0.41% at the 2.5×10^-5M thiosulfate level. The proposed method was successfully applied to the determination of thiosulfate in hot spring and lake waters.

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A highly sensitive, rapid and facile method of fluorophotometry is described for the determination of phosphate using the ion pair formation of molybdophosphate with Rhodamine 6G. This ion pair is collected on a membrane filter made of cellulose nitrate when the sample solution is adjusted to 0.35mol dm^-3 in sulfuric acid, 1.9mmol dm^-3 in ammonium molybdate and 3.1μmol dm^-3 in Rhodamine 6G, and it is filtered through the membrane filter under suction. The membrane filter together with the ion pair is dissolved into Methyl Cellosolve. The fluorescence intensity of this solution is measured at 555nm with the excitation at 535nm. The calibration curve of phosphate is linear from 5 to 100ng of phosphorus, with the correlation coefficient of 0.999; the relative standard deviation was 1.6% for 100ng of phosphorus (n=12). Although arsenic(V) causes positive error, no ions, including silicate, commonly existing in natural water interfere with the determination of phosphate. The proposed method was applied to the determination of phosphate-phosphorus in water samples and satisfactory results were obtained.

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A simple and sensitive method to evaluate the antioxidant activity using a chemiluminescence system was newly devised. Chemiluminescence, generated from the reaction of a luminescent reagent with lipid hydroperoxides, was detected using a chemiluminescence analyzer. Added antioxidants inhibited the progress of the reaction and decreased the chemiluminescence intensity. Effectivity of antioxidants which could be estimated from the inhibition of chemiluminescence indicated a good agreement with that estimated by the thiocyanate method, except for α-tocopherol. This method was improved for the screening of 236 species of edible and medicinal plants for antioxidant activity.

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A catalytic-photometric method with a continuous-flow system was developed for the determination of nanogram amounts of manganese. The method is based on its catalytic effect on the oxidative coupling reaction of 3-methyl-2-benzothiazolinone hydrazone with N, N-dimethylaniline to form a blue-violet compound (λ_max=590nm) in the presence of hydrogen peroxide. In this reaction, 1, 10-phenanthroline and citrate acted as activators for the catalytic action of manganese(II). Manganese(II) at the 2-30ng ml^-1 level can be determined at a rate of 10 samples h^-1. The method
can be applied to the determination of manganese in biological materials.

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A novel flow injection method has been developed for the determination of selenium in biological samples. The method is based on a selective catalytic effect of Se(IV) on the reduction of 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2H tetrazolium bromide (MTT). The calibration line ranged over 1.3pmol to 1.2nmol of selenite with a detection limit of 0.63pmol. Interference from the copper ion could be eliminated by an on-line adsorption of Cu on an ODS column as a Cu-bathocuproine Bisulfate chelate. The utility of the method was demonstrated by determining the selenium content in a standard sample.

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A sensitive single sweep polarographic peak, related to the nitrite concentration, appears in a slightly acidic solution containing nitrite and thiourea. The peak is ascribed to the reduction of formamidine disulfide (RSSR) resulting from the reaction between nitrite and thiourea. The reduction process involves a slow conversion of this disulfide to mercury sulfide, i.e.a preceding reaction mechanism. The method is used to determine trace concentrations of nitrite, with a detection limit of 5×10^-7mol/dm³. The sensitivity increases ten times when catholic stripping voltammetry is used at the static mercury electrode.

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The effect of complexing agents on the titration of vanadium(V) with iron(II) was studied. Complexing agents which form more stable complexes with iron(III) than iron(II) produce a sharper titration of vanadium(V) with Iron(II). Citrate, pyrophosphate and EDTA improve the potential break at the equivalence point. The presence of excess EDTA decreases the formal potential of the V(V)/V(IV) couple due to the formation of vanadium(V)-EDTA complexes. The use of a ligand buffer with zinc(II) in excess over EDTA is very effective for improving the end-point detection in the titration, preventing the formation of vanadium(V)-EDTA complexes.

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Novel pyridylformazane derivatives have been synthesized by introducing various substituents into a benzene ring. Their characteristics as analytical reagents, such as acid dissociation constants and color reactions with various transition metal ions, have been investigated. A linear relationship has been established between Hammett′s substituent constants (σ) and acid dissociation constants (pk_a1, and pk_a2), and between (σ) and stability constants of metal complexes. Introduction of a nitro group into mesa- or para-position of the benzene ring has increased the sensitivity to a great extent; the molar absorption coefficient (logε) of the zinc complex was 4.91 and the stability constant (log K_ZnA2) was 18.97±0.05.

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The solvent extraction of lanthanoid ions with N-p-methoxy (MBPHA) and N-p-octyloxy (OBPHA) derivatives of N-benzoyl-N-phenylhydroxylamine (BPHA) in chloroform was studied. The selected lanthanoids (Yb, Ho, Eu, Pr and La) were all found to extract with compounds as self-adducts of the form LnL₃mHL, (m=1 for BPHA, 2 for MBPHA and 3 for OBPHA), where L and HL denote the ligand anion and neutral ligand, respectively. The extraction constants and separation factors for the lanthanoids with MBPHA and OBPHA were evaluated.

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The contribution of substituent groups to the extractability of phenols and benzoic acids was examined by using a substituent constant, π, derived from the distribution coefficients of nonionic substances. This constant is defined as π_X=log K_D(X)-log K_D(H), where K_D(X) is the distribution coefficient of a derivative and log K_D(H) is that of the parent compound. The substituent constants of the groups at the ortho-position of phenol were found to vary with a variation of the extraction solvent, possibly due to competition between the hydration and solvation of an organic solvent. From the K_D values of the phenols and benzoic acids determined between chloroform and water, the substituent constants of halogeno, cyano, trifluoromethyl and nitro groups were calculated. In phenols, the π values of the ortho-substituting group (π^o) were greater than those of the meta- and para-substituting group, π^m and π^p, respectively, whereas in benzoic acids π^o are smaller than π^m and π^p. Such results can be explained by a masking effect and the overlapping effect: the masking effect increases the π^o values, whereas the overlapping effect decreases the π^o values. A method for predicting the total π values of di- and tri-substituted phenols and benzoic acids is proposed.

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The kinetics of the extractions of copper(II) and nickel(II) with 2′-hydroxy-5′-nonylbenzophenone oxime (HL) in heptane was studied by means of a high-speed stirring apparatus. Linear correlations were established between the initial extraction rate of the metal ions and the amount of HL adsorbed at the liquid-liquid interface. The ratecontrolling step was the reaction between L^- at the interface and the metal ions in aqueous phase adjacent to the interface. A solvent effect of heptane and chloroform on the interfacial mechanism of the extraction of nickel(II) was also examined.

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The enhancement of the concentration of analytes by a feed/receiving volume effect in coupled membrane transport was both theoretically and experimentally investigated in view of the designs of uphill transport membrane sensors and novel preconcentration techniques in general. Theoretical equations for the feed/receiving volume effect were derived for the membrane diffusion-limited co-transport and counter transport cases. The theoretical results coincided well with the volume effect observed experimentally for some representative liquid membrane systems, in which the concentration of an analyte in the receiving solution was found to increase upon decreasing the volume of the receiving (inner filling) solution. The complexation reaction of an analyte in the receiving solution was found to be useful as an additional driving force for further enhancing the analyte concentration by coupled transport.

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