Adsorption characters of various organics on activated carbon fiber (ACF) have been studied. ACF of cellulose resin base and of phenol resin base, which have a lot of micropores (D=1-2 nm) are used as adsorbents, and these are treated with hydrogen gas at 1000°C to eliminate groups on the ACFs' surface. The adsorbed amounts of organics for the unmodified ACF are not so much as that for an usual carbon adsorbent. Even when the surface-modified ACF are used, the adsorbed amounts of large molecular size organics are smaller than that for the carbon adsorbent with mesopores. However, the adsorbed amounts of small molecular size organics are particularly large for the surfacemodified ACF. This may be caused by a lot of micropores existing. The adsorption character of organics is highly dependent on the pore size distribution of adsorbents. Moreover, it is also of importance to eliminate surface groups from adsorbents.

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Various kinds of gases and liquids are separated via their interaction with the surface and pores of silica gels. This report describes the properties of surface and po res of high purity silica gels and their modification with ethanol and (3-aminopropyl)triethoxysilazie.

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The authors have just started a study to develop simple analytical methods of natural and environmental waters which can be widely used without any expensive instruments. As a part of the study, a preconcentration method for fluoride ion in aqueous solution has been investigated.
An effec tive and simple method for preconcentration of fluoride ion in aqueous solution has been developed by use of activated carbon loaded with zirconium (Zr-C*). The Zr-C* was prepared by mixing 100 ml of zirconium(W) nitrate oxide solution (1 g Zr, pH 1.6)with 10 g of activated carbon at room temperature for three days, filtering and drying the residue in air. Ten grams of the resulting activated carbon included O.5 to 0.6 g of zirconium.
The established method for concentration of fluoride ion in aqueous solution is as follo ws: Af ter adjusting the pH of sample solution (O.1 to 10l) to 3.7±0.3, the solution is passed through the Zr-C* bed (0.5 g) with the aid of a device as shown in Fig.1. The fluoride adsorbed on the Zr-C* is eluted with 40 ml of 0.02 moldm^-3 sodium hydroxide solution, then the recovered fluoride ion was determined photometrically with lanthanum alizarin complexon.
As seen in Fig.2, Zr-C* adsorbs fluoride ion quantitatively at the pH 4.5 or below and scarcely at the pH above 9.0, and the desorption of fluoride ion from Zr -C* occurs quantitati vely at the pH 9.0 or above. Thus, the adsorption and desorption only depend on the pH of the solution. Because the adsorption and desorption of -fluoride ion are accomplished instantaneously, zirconium seems to be loaded only on the surface of activated carbon. These characteristics of Zr-C* are favorable for rapid concentration of fluoride ion in a large volume of sample solution (10 1/2 h). Large amounts of phosphate and sulfate which react with zirconium give a low recovery of fluoride. In the presence of metal ions which form the complex with fluoride ion such as aluminum and iron ions, addition of acetylacetone is recommended as a demasking agent.

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The selective adsorption of metal ions with activated carbon impregnated 2, 4, 6-tri-2pyridy1-1, 3, 5-triazine (TPTZ-AC) was studied for the preconcentration of traces of cadmium(II) and copper(II) ions. TPTZ-AC was prepared as follows 5.0 g of activated carbon and 2.0 g of TPTZ are added into 50 cm³ of 3 mol⋅dm^-3 hydrochloric acid. The mixture is stirred 30 min and TPTZ-AC is filtrated after standing for one day, and then it is dried in an oven at 110°C for 2 h. 0.5 μg of cadmium(II), 20 μg of copper(II)and lead(II) were collected completely from 100 cm³ solution in the presence of 5 cm³ of 2% potassium iodide over the pH ranges 5.0-11.0, 4.0-9.0 and 5.0-8.0 respectivery, by stirring with 50 mg TPTZ-AC for 10 min, but nickel(II) and cobalt(II) were not collected quantitatively. Cadmium(II) and copper(II) in the presence of iron010 and aluminum(III) (each 50 mg) were collected completely over the pH range 5.0-8.0. Leadan was not collected selectively. Adsorption time was 10 min in a ultrasonication bath using 50 mg of TPTZ-AC and desorption of adsorbed metals took 5 min in the bath using 1-5moldm^-3 nitric acid. The composition of complex formed with cadmium(II) or copper(II), TPTZ and iodide ion were 1: 1: 2, respectively. The proposed method was successfully applied to the determination of cadmium and copper in several sediments by atomic absorption spectrometry. This method is very simple and rapid, and is suitable for the determination of trace amounts of cadmium(II) and copper(II) in the sample containing large amounts of iron(III) and aluminum(III).

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New ion-exchange resins for the selective adsorption of noble metal ions are prepared by loading trioctylamine (TOA) onto macroreticular hydrophobic resins. The prepared resins reveal adsorption characteristics similar to those for the commercial anion-exchange resins, whereas their elution processes are entirely different from those of the commercial resins, i. e., gold(III), platinum(IV) and palladium(II) are readily adsorbed on the present resins as anionic chloro complexes, and easily liberated from the resins as ion pairs with protonated TOA by elution with 4-methyl-2-pentanone.
The adsorption characteristics of the resins for those noble metal ions have been studied. The adsorption efficiency of the present resin is closely related to the specific surface area and hydrophobic property of the resin matrix and also the amount of TOA loaded. The optimal adsorption efficiency is obtained by the treatment of XAD-7 with 1 mmol (g-resin)^-1 of TOA. The distribution coefficients of the resin for gold(III), platinum(IV)and palladium(II) are 10^4.6, 10^3.6 and 10^3.2, respectively, in 1 mol·dm^-3 HCI solution.
The selective recovery of gold and platinum from the acid-leaching solution s of industrial scraps has been demonstrated by means of the column operation. The breakthrough capacities for gold and platinum are approximately 62 g (kg-resin)^-1 and 37 g (kg-resin)^-1, respectively. Excess amount of other common metal ions including aluminum(III) and copper (II) have not been adsorbed on the resin, and immediately leaked out of the column.

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Polymeric d-camphor and l-menthol membranes were prepared by plasma polymerization, and permeation and adsorption characteristics of amino acids by these membranes were investigated.
It was found that plasma-polymerized d-camphor and l-menthol membranes possessed fairly the structure of their starting compounds and that the permeabilities for aqueous D-tryptophan and D-proline were different from those of L-amino acids.
It was also found that silica particles, the surface of which was covered with plasmapolymerized d-camphor membranes, adsorbed L-tryptophan preferably to D-tryptophan.

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Optically active d-camphor and 1-menthol membranes were prepared by plasma polymerization and their structures were investigated.
Thickness and specific rotatory po wer of the membrane were strongly dependent on the position of the substrate. The membrane was formed most rapidly at the edge of electrodes where current density is supposed to be the highest. Specific rotatory power of the membrane increased with increasing distance of the substrate from the electrode and the value of the membrane deposited in the after glow region was several times greater than that of the starting compound. The variation of specific rotatory power of these membranes was associated with substitution reaction of the groups bound to the optically active carbon.
¹H-NMR, ¹³C-NMR, IR studies of these membrane were carried out and the possible structure of the membranes were discussed.

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The adsorption of phenols from aqueous solution by silicalite, an aluminium-free analogue of zeolite ZSM-5, has been investigated at 25°C. Silicalite selectively adsorbs phenols having the molecular size smaller than the pore size (ca. O.6 nm), and the Langmuir isotherm can be applied in all cases. The distribution coefficients (α) defined by Eq.2were calculated and are given in Table 1. A good linear relationship is seen to exist between α and the carbon number of phenols (Fig.2) and also between α and the solubility of phenols in water (Fig.3). The amount of phenols adsorbed increases with an increase in the carbon number and with a decrease in the solubility.

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The synergistic extraction of cobalt(II) with dithizone(H2dz) and 2, 2'-bipyridyl(bpy)was shown to proceed according to the following equation;
Co²⁺+2H₂dz_org+2bpy_org⇔Co(Hdz)₂(bpy)2_org+2H⁺
where the subscript org denotes the chloroform phase. The extraction constant for the above reaction was estimated to be Kex =107.6. On the other hand, a kinetic approach was applied to the synergistic extraction of nickel(II), whose reaction with a chelating agent generally proceeds rather slowly. The rate-determining step of nickel(II) extraction was estimated to be the formation of Ni(bpy)₂(Hdz)⁺ in the aqueous phase;
Ni(bpy)₂²⁺+Hdz- → Ni(bpy)₂(Hdz)⁺
the rate constant for the reaction being k₂=7.5×10⁴ mol^-1·dma·s^-1 (ca.293 K). By using the present system, the percent extraction of cobalt(II) is enhanced synergistically and at the same time, one can find conditions in which the extractability of nickel(II) remains low due to the small rate of extraction. As a result, mutual separation of cobalt(II) and nickel(II) was performed by shaking the aqueous phase (pH =6.2) containing both i ons with a mixture of dithizone (2.00×10^-4 mol·dm^-3) and bpy (4.00×10^-2 mol·dm^-3) for 30 s.

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Two procedures have been described for extraction of gold(III) with a nonionic surfactant from hydrochloric acid solution. The surfactant used was poly(oxyethylene) 4-nonylphenyl ether with an average number of oxyethylene units 7.5 (PONPE-7.5). One procedure utilizes the cloud point of the surfactant; at a temperature above the cloud point, a surfactant-rich phase is separated from aqueous solution, and gold is extracted into this phase. In this procedure, 30 g of 0.1 mol·kg^-1 of hydrochloric acid solution containing 30-3000 μg of gold and 0.3 g of PONPE-7.5 was heated at 40°C in a water bath for 10 min and then centrifuged. The centrifuge tube was cooled at about 10°C for 1 min, and the aqueous phase (upper layer) was removed, leaving the extract (about 2 g) in the tube. One and half gram of 20% w/w PONPE-20 solution was added to make the extract clear, and water was added to make the solution 5.00 g. Absorbance of this solution was measured at 335 nm to determine gold. Ninety-five% of gold was extracted. Effect of foreign metals is shown in Table 1. Another procedure involves extraction of gold with a 1, 2-dichloroethane solution of PONPE-7.5. In this procedure, 25 cm'of 2 mol·kg^-3 hydrochloric acid solution containing 50-5000 μg of gold was shaken with 5 cm' of 5% w/v PONPE-7.5 in 1, 2-dichloroethane for 5 min. The extract was diluted to 10 cm³ and the absorbance was measured at 325 nm. Ninety-seven to 98% of gold was extracted. Effect of foreign metals is shown in Table 2.

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It was shown in the preceding paper that the extraction constant (K_ex) for 1: 1 ion-pair extraction systems can be expressed as a product of three independent constants (individual extraction constants), namely,
logK_ex=logK_cation+log_anion+logK_solvent
where K_cation, K_anion and K_solvent are the individual extraction constants for the cation, anion and solvent, respectively. In the present paper, the individual extraction constants was assigned to some ions and solvents on the assumption
K_ph4As++=K_Pb4B-, K_benzene=1.0
The assigned values of individual extraction constants were shown to be useful in estimating the value of K. for unknown combinations of cation, anion and solvent and in estimating the extractabilities of ions and extracting powers of the solvents.

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Distribution equilibria of 2-(2-pyridylazo)phenol (PAP), 2-(2-thiazolylazo)-4-methylphenol (TAC), 2-(2-thiazolylazo)-5-dimethylaminophenol (TAM) and PAP chelates of nickel(II), zinc(II) and cadmium(II) have been studied between two phases (surfactant and aqueo us phases) which were formed from a micellar solution of poly(oxyethylene) 4-nonylphenyl ether with on oxyethylene units of 7.5 on the average (PONPE-7.5). On the basis of the distribution curves for the chelating reagents and the PAP chelates as a function of pH, the acid dissociation constants and partition constants of the reagents and the stability constants and the partition constants of the chelates were determined at 293 K and ionic strength of μ-O.1 (NaCl). The equilibrium constants thus obtained were summarized in Tables 2 and 3. The reagents were extracted not only with the uncharged form (HL) but also with the charged form probably as the type Na⁺L^- and H₂L⁺Cl^-. Relatively large values of the partition constants for the negatively charged species (L^-)suggest that L^-is extracted as an ionic associate with the Na⁺ ion that is complexed with the ether oxygen of PONPE-7.5. The partition constant of the neutral chelates (K_D2) depends on the kind of metal ions and is considerably smaller than those e xpected from the regular solution theory. These facts suggest that the chelates are incoporated into a hydrocarbon environment in the surfactant phase, whereas the reagents are distributed into the poly(oxyethylene) part of PONPE-7.5.

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Two new thiacrown ethers in which the dinitro(trifluoromethyl)phenylamino group are introduced as the chromogenic group, 13, 14-[4-[(2, 4-dinitro-6-trifluoromethylphenyl)amino]benzo]-1, 4, 8, 11-tetrathiacyclopentadec-13-ene[4] and 13, 14-[4-[(2, 6-dinitro-4-trifluoromethylphenyl)amino]benzo]-1, 4, 8, 11-tetrathiacyclopentadec-13-ene[5] have been synthesized and their characteristics as extracting and spectrophotometric reagents have been examined and compared to 4-(picrylaminobenzo)-1, 4, 8, 11-tetrathiacyclopentadec-13-ene[3]. These two compounds, [4] and [5] as well as [3] react selectively with univalent class b metals and form intra-molecular pair complexes, which are extracted into organic solvents. Silver( I ) was chosen as a typical class b metal for the study. Less overlap of the absorption spectra of HL and L^- in 50% dioxane-water mixture was found for reagents [4] and [5] as compared with the reagent [3]. Similarly, overlaps of ab sorption spectra of HL and AgL for reagents [4] and [5] in 1, 2-dichloroethane are less than that for the reagent [3]. The pK_a of the reagent [4] in 50% dioxane-water mixture, 9.85, is similar to that of [3], but that of the reagent [5] is very high, >13. It was concluded that the reagent [4] is the best one for the extraction and spectrophotometric determination of univalent class b metals such as Ag(I) and Cu(I). Silver(I) is cornpletely extracted with the reagent [4] into 1, 2-dichloroethane from aqueous solution above pH 8. The interference from Mn(II), co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Fe(III) in the presence of 0.1 rnolidm-3 tartrate as a masking agent was examined. Co(II), Cu(II), Zn(II), Cd(II) and Fe(III) with a 200 fold amount relative to silver do not interfere with the extraction and spectrophotometric determination of Ag(I) using the reagent [4].

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The effect of tetrabutylammonium ion(TBA⁺) on the solvent extraction of cobalt (II)in aqueous 1 mol/dm³ sodium chloride solution with 5 different β-diketones (HA) was studied. The effect was found to be negligible on the extraction with acetylacetone and benzoylacetone while the addition of this bulky cation increased that with trifluoroacetylacetone and benzoyltrifluoroacetone. It also increased the extraction with hexafluoroacetylacetone more than that with these two β-diketones having one trifluoromethyl group. The increase was concluded to be due to an extraction of the CoA₃^-TBA⁺ species in addition to that of the uncharged CoA₂ species. The chemical equilibria of the extractions of these binary and ternary complexes were analyzed and the relation between the chemical properties of the β-diketone and the stability as well as the extractability of the ternary complex was considered.

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A flow injection system with a stream-switching valve for continuous monitoring of the isozyme activity of lactic dehydrogenase (EC 1.1.1.27, LDH) after liquid chromatographic separation is described.
Sample injec ted into micro column (1.5φ×20 mm) system of DEAE-sepharose and QAEsephadex, was eluted stepwise with Tris-buffered sodium chloride (15, 30, 75, 100 and 150 mmol·dm^-3). The separated isozymes were subsequently mixed with the enzyme reagen ts and immediately passed to the fluorescence detector to measure a sample background before the beginning of the enzyme reaction. After the initial measurement of background fluorescence, the mixture, which was passed to the reaction coil by the stream-switching valve, underwent a series of enzyme reactions, ultimately resulting in the formation of NADH. The fluorescence intensity of NADH was measured finally with the same detector.
Isozyme activity was determined by subtracting the area of sample background from the area of fluorescent NADH.
A major advantage of this detection system is the ability to carry out continuous monitoring of the isozyme activity and the sample background. In addition, LDH isozyme in urine containing salt s and inhibitors is purified and measured successfully by using a corridor of a hollow fiber (cuprammonium rayon) on lined to the flow injection system.
The present devic e is useful for the measurement of isozyme activity in various biological samples.

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Separation of β- and γ-picolines by clathrate complex formation with 1, 1, 6, 6-tetraphenyl -2, 4-hexadiyne-1, 6-diol [1] and 1, 1, 2, 2-tetraphenyl-1, 2-ethanediol [2] has been studied. Studies on selectivity of inclusion of [1] and [2] for picoline isomers using various kinds of picoline mixtures showed that β-picoline is included predominantly when its content in a mixture is higher and γ-picoline is included predominantly when its content is higher. This selectivity changed depending on the ratio of host: picoline and on the kind of solvent. It was finally clarified that β- and γ-picolines can be easily separated by using the above phenomena.

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It has been found that 1, 1, 6, 6-tetrapheny1-2, 4-hexadiyne-1, 6-diol [1] and 1, 1, 6, 6-tetrakis (2, 4-dimethylphenyl)-2, 4-hexadiyne-1, 6-diol [2] well recognizes a slight difference of shape of guest molecules and include them selectively. This selective inclusion phenomena of [1] and [2] can be used for efficient separation of the following isomers: o- and pdisubstituted benzene derivative, cis- and trans-2-butene-1, 4-diol, and meso-and dl-3, 5dimethylcyclohexanone.

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The rate of electroosmotic flow could be controlled by the material of capillary column, the concentration of electrolyte, the addition of the surface active reagent in the s olution, the applied voltage and current, etc.
For liquid chromatography using a capillary column (0.4 mm i. d.×9 cm), pyrene (k' =1.2)is eluted out within 6 min by appling 9 kV. A characteristic point is that there is no pressure drop due to the electroosmotic flow. Therefore, this method would be applicable to liquid chromatography with very soft gels.
When the electroosmotic flow is used for zone electrophoresis, it becomes possible to be a separation with elution Simple components whose absolute mobilities are less than the rate of electroosmotic flow, could be carried to the end of capillary column. The separations of metal ions and amino acid derivatives are demonstrated.

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A sensitive capillary isotachophoretic method (CITP) in non-aqueous systems was developed. for the simultaneous determination of heavy metal ions extracted as the diethyldithiocarbamate (DDTC) chelates. Perchlorate, chloride and hydrogen ions were used as a leading (0.005 mol·dm^-3), a terminating (0.01 mol·dm^-3) and a counter ions, respectively; N, Ndimethylfgrmarnide (DMF) was used for the solvent of migrating system.1, 2-Dichloroethane and nitrobenzene were found to be most suitable solvent for the extraction of metal chelates and the extracts could be injected as sample solution for CITP without any pretreatment. The tolerable injection-amounts of the solvents, 1, 2-dichloroethane and nitrobenzene were 20 and 25 μl, respectively. The DDTC chelates injected are converted into the corresponding chloro complex anions by reaction with the counter cation H+and terminating anion Cl^-. The reaction is represented for divalent metal ion as follows,
M(DDTC)₂+2H⁺+nCl^- [MCl_n]^(n-2)-+2H·DDTC
The separation was achieved through the equilibria among the chloro complexes with the chloride and the 'hydrogen ions supplied from the terminating, leading zones, respectively. The H·DDTC liberated was readily decomposed to diethylammonium ion and carbon disulfide under the system. The calibration curves obtained by injecting 10 μi of DDTC chelate extracts from mixed solution of Fe(III), Cd(II), Zn(II), Pb(II) and Mn(II) were found to be linear in the range of 2-10 nmol. The proposed method was also applicable to the separation of trace metal ions shown in Fig.8 at the concentration as low as 1×10^-6mol·dm^-3. The order of decreasing effective mobilities of the chloro complexes in this system was Ga(III), Fe(III), Hg(II), Cd(II), Zn(II), Sb(III), Pb(II), Mn(II) and In(III).

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When a DC high voltage is applied between the both ends of an open-tubular capillary filled with an ionic surfactant solution, the whole solution is transported by the electroosmotic flow, while the charged micelle migrates with a different velocity from that of the solution because of an electrophoretic effect. In other words, electroosmotic and electrophoretic effects cause the differential migration between the micelle and the surrounding aqueous phase. A solute added into the surfactant solution distributes itself between the micelle and the aqueous phase. Electrokinetic chromatography, which is based on the combination of the electrokinetic migrations and the micellar solubilization phenomenon, was applied to the separation of seven alkyl phenyl sulfides whose alkyl groups were methyl, ethyl, propyl, isopropyl, butyl, isobutyl and s-butyl, and four alkyl benzyl sulfides whose alkyl groups were methyl, ethyl, propyl and isopropyl. The ten sulfides among the eleven were separated by a 0.05 mm i. d. × 900 mm fused silica tube filled with a 0.02 mol·dm^-3 sodium dodecyl sulfate solution (pH 7.0) at ambient temperature. Distribution coefficients of the sulfides in micellar solubilization were calculated for sodium dodecyl sulfate and sodium tetradecyl sulfate solutions at 35°C. The use of a mixed solution of 80% of a 0.03 mol·dm^-3 sodium dodecyl sulfate solution (pH 7.0) and 20% of methanol gave also successful separation of the ten aromatic sulfides among the eleven. The unresolved pair was different from that observed with a O.02 mol·dm^-3 sodium dodecyl sulfate solution.

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Electrochemical studies on the ion transfer across the interface between immiscible organic and aqueous electrolyte solutions (oil/water interface) indicate that an oil/water interface works satisfactorily as an ion-selective electrode interface for both amperometric (or voltammetric)and potentiometric analyses of ions. The presence of an ionophore, which specifically binds an ion in the oil phase, renders the interface ion-selective for the ion. This was experimentally demonstrated for the transfer of sodium, potassium, rubidium, cesium, and ammonium ions across the ionophore(L)-containing nitrobenzene/water interface, where L is dibenzo-18-crown-6 (DB 18 C 6), and of sodium and potassium ions across the Lcontaining nitrobenzene/water interface, where L is bis[(benzo-15-crown-5)-4'-ylmethyl]pimerate (BB 15 C 5), DB 18 C 6, dibenzo-24-crown-8 (DB 24 C 8), or dicyclohexano-18--crown-6(DC 18 C 6, isomeric mixture). Theoretical and experimental examinations show that the ion-selective oil/water interface permits two types of electrochemical analyses of ions: amperometry (or voltammetry) and potentiometry. In other words, the oil/water interface can function either as an amperometric (or voltammetric) ion-selective electrode or as a potentiometric ion-selective electrode. The former gives the current response proportional to the concentration of ion, whereas the latter the potential response linear to the logarithm of ion activity (concentration). An advantage of the voltammetric method over the potentiometic one is that two or more ions can be simultaneously determined if their half-wave potentials are reasonably separated. This was experimentally verified for simultaneous determination of sodium and potassium ions using a voltammetric ion-selective electrode based on the DB 15 C 5-containing nitrobenzene/water interface. Other important features of the two types of the electrochemical analyses are discussed.

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A micro-scale chromatograph that facilitates the employment of modified carbon dioxide as the mobile phase with a single pump was assernMed. Carbon dioxide was modified in a 40 ml mixing chamber and the separation was carried out below the critical temperature of carbon dioxide. Liquid chromatographic retention behaviours of aromatic and polycyclic compounds by a liquid carbon dioxide elution were examined in this work. Relative standard deviations of the capacity factor of polycyclic aromatic hydrocarbons were 5-8%. The retention of test solutes had tendency to decrase with increasing the methanol concentration in the mobile phase when “Develosil ODS”, and silica-gel columns were used The system was applied to the resolution of enantiomers with the chiral stationary phase.

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The retention time of nonionic compounds was predicted from their Van der Waals volume, π-energy and hydrogen-bonding energy effects in reversed-phase-mode liquid chromatography using octadecyl-bonded silica gels. For ionic compounds like acids, their dissociation constants were further added into the above relation. However, the optimization on ionexchangers was difficult because ion-ion interaction was unpredictable and the work of the silanol group on the surface of chemically-modified silica gels was uncertain. Therefore, the selectivity and the specificity of rigid vinyl alcohol copolymer gels were examined in reversed-phase-mode liquid chromatography. The standard compounds were alkanes, alkanols, alkylbenzenes, aromatic carboxylic acids and polycyclic aromatic hydrocarbons. The results were compared with those obtained on chemically-bonded silica gels. The selectivity of vinyl alcohol copolymer gels to polycyclic aromatic hydroc arbons was very weak compared to that of polystyrene gels, but was stronger than that of octadecyl bonded silica gels.
The selectivity was explained as the difference of the energy effect of the retention of these compounds. The results obtained on ion-exchange vinyl alcohol copolymer gels demonstrated that their dissociation constants were regularly shifted but the shift was not the same as that obtained on modified silica gels.

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Reversed phase liquid chromatography (RPLC), the most widely used mode in highperformance liquid chromatography, commonly uses silica gel as a support material for columns, on which octadecyl chain is chemically grafted. In RPLC, the solvophobic theory has been used to explain the retention mechanisms of hydrophobic or partly hydrop hobic solutes on RPLC columns, but we have still some problems that can not be explained by the theory. An example is the fact that nucleosides having a hydrophilic ribose ring show more preferential retention on silica-based RPLC columns (ODS columns) than their corresponding bases which are highly hydrophobic. Two possible factors for this unusual retention are the unusual hydrophobic interaction between solutes and octadecyl chains and the specific interaction of solutes with silica gel. In order to elucidate this fact, vinyl alcohol copolymer gel, whose retention mechanism for such solutes has been explained by the solvophobic theory, was taken as a support material and the retention of nucleosides and their bases were investigated on a column packed with octadecyl chain-grafted vinyl alcohol copolymer gel. It was revealed that the retention of all samples on the packing was well explained by the solvophobic theory and such samples were adsorbed on an ODS silicagel with unusual retention behavior. The extraordinary long retention of adenosine 3', 5'-cyclic phosphate on ODS silica columns was determined to be due to the similar interaction between silica gel and the solutes.

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A wide variety of commercially available liquid chromatography instruments (LC) now completely satisfy the requirements of most routine analytical and semipreparative separations. However, the selection of satisfactory separation conditions is still a major problem in LC. Recent advancements in computer technology now offer us very valuable and useful microcomputers, which can make the situation for finding the desired separation conditions convenient and time-saving. This contribution describes the computer-assisted strategy, i. e., the role of computer in LC, to identify benzo [a] pyrene in a sample as the test solute, which is one of the most important substances in environmental analysis.
In this strategy, information on LC systems suitable for solving an alytical problems, identification of benzo [a] pyrene in this case, can be obtained by retrieving references stored in a data base system and optimization can be performed by a retention prediction system based on the theoretical models of LC separations. The solute in complex mixtures that appears in chromatogram can be easily identified by the use of a computerized UV multichannel detection system. All the systems were controlled by microcomputers. As the results, it has been realized that the approach could be applied to practical analytical problems even though the strategy described in this investigation has been focused on only one solute.

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A channel thin-layer cell with a copper working electrode has been used as a directly amperometric detector for amino acids in high-performance liquid chromatography. All essential amino acids except cysteine gave the increase of the anodic dissolution current at the copper electrode by the reaction of copper(II) ions with amino acids at -20 m V vs. Ag/AgCl. The amperometric response of amino acids is dependent on their properti es and correlated to the acid dissociation constant of amino group of amino acids. This evidence indicates that the cell reaction is controlled by the rate of the complex formation of copper(II) ion with amino acid. A favorable S/N ratio was obtained with the cell geometry of the channel height and width of O.1 mm and O.5 mm, respectively, at the flow rate of 0.5 ml/min using 0.1 mol·dm^-3 phosphate buffer (pH 7.0)/methanol 9: 1 as the mobile phase. Although all essential amino acids were not well separated with a reverse phase column, the wide linear dynamic range more than three orders was obtained. The detection limit (S/N=2) was 20 pmol for histidine, 2 nmol for proline, and subnanomole order for other amino acids. The proposed electrochemical method is straightforward and simple compared with other detection methods.

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Separations of positional isomers and geometrical isomers of unsaturated compounds were examined by using octadecylsilylated (C₁₈) phase and 2-(1-pyrenyl)ethylsilylated (PYE)phase on silica gel in reversed-phase liquid chromatography.
C₁₈ phase showed preferential retention of solutes with double bonds at an internal position and with E configuration. The results can be explained in terms of the hydrophobic property of each solute. The interaction between double bonds in a solute and pyrene rings of PYE phase contributed to the unique selectivity of this stationary phase. Stronger interactions were observed with a double bond at a terminal position and with an internal double bond with Z configuration. The tendency can be explained by the steric effect of substituents on the sp² carbon atoms. The electronic interaction was pronounced in a mobile phase of high methanol contents, because of the smaller contribution of hydrophobic interaction in such a mobile phase. In the case of unsaturated carboxylic acid derivatives, PYE phase showed preferential retention for solutes possessing double bonds away from the carboxyl group, and provided separation between linolenic acid and γ-linolenic acid, which cannot be separated by C₁₈ phase.
The complementary use of PYE phase, which has widely different selectivity, with C₁₈phase will increase the capability of reversed-phase liquid chromatography.

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Two novel chiral stationary phases derived from (R)- and (S)-1-(1-naphthyl) ethylamine with (R)-phenylglycine chemically bonded to (3-aminopropyl)silanized silica, [5] and [6], which contain two asymmetric carbon atoms attached to two nitrogen atoms of the ureylene group, have been prepared. These phases showed good enantioselectivity for derivatives of amino acid, amine, carboxylic acid and alcohol enantiomers. Especially excellent separation factors were obtained in enantiomeric separation of aromatic amine and carboxylic acid in the form of 3, 5-dinitrobenzoyl and 3, 5-dinitroanilide derivatives respectively upon phase [6]. It is noticed some enantiomers were resolved directly without any prederivatization on these phases. For example, enantiomers of both E- and Z-isomers of S-3308 (1-(2, 4- di chloropheny1)-4, 4-dimethy1-2-(l, 2, 4-triazol-1-y1)-1-penten-3-ol) are well resolved simul taneously with [5].

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The retention behaviors of various amino acids, corresponding amines, and peptides in a reversed phase high performance liquid chromatography with crown ether-cont aining mobile phases have been investigated, and the results were compared with those obtained in the ion-pair reversed phase chromatography.
The capacity factors were in c reased by the addition of 18-crown-6 in the mobile phase according to the association between 18-crown-6 and the protonated primary amino g roup of amino acid. The extent of the increase varied with the configuration around the amino group more specifically than observed in the ion-pair chromatography; the ami no acid bearing lower class carbon atom(s) at α- or β-position showed the higher extent of the increase. Lysine, which has another amino group on its lateral chain, showed the larger increase than histidine and arginine, while all these basic amino acids ind icated almost the same degree of increase in the ion-pair mode. However, proline, which does not have a primary amino group, showed decreased capacity factor, while it showed increa sed capacity factor in the ion-pair chromatography. The addition of 18-crown-6 caused larger difference in the capacity factors between amino acid and the corresponding amine than that of the ion-pair reagent, indicating that the stronger hindrance stemmed from the carboxyl group in the association of the α-amino group with 18-crown-6.
Like amino acids, the changes in the capacity factors of pe p tides caused by the addition of 18-crown-6 were significantly dependent on the structure of the N-terminal amino acid residue. The complex formation between 18-crown-6 and peptides with a branched carbon atom at β-position in the N-terminal residue caused relatively small enhancement of the capacity factor. The formation constant was also small.
The structure -recognizing ability of 18-crown-6 enabled the rapid and effective separation of amino compounds which was difficult in the conventional reversed phase ion-pair chromatography. Several examples of amino acids or peptides by the proposed technique are demonstrated.

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A highly sensitive and selective fluores, cence high-performance liquid chromatography using 9-anthryldiazomethane as a pre-labeling reagent was applied to the separation and determination of icosapentaenoic acid (IPA) and arachidonic acid (AA) at nanogram level in ovary and testis of several adult fishes and plankton lived in the sea area of Micronesia.
Then, a tendency of IPA and AA contents, as a precursor of prostaglandins, in the both reproductive organs of fishes and plankton has partially been revealed by the present work.
The limit of detection and the coefficient of variation of IPA and AA in the reproductive organs of fishes obtained by the present method are about 2 ng and 7.7%, respectively. In the range of our experiments, IPA contents in their reproductive organ s of Euthynnus pelamis (female and male), Coryphaena hippurus (female), Scomberomorus niphonius (male)and Cuttlefish (female) were remarkably higher than those of the other fishes, and also IPA contents in several plankton taken in this sea area were significantly high as compared with those of plankton of Lake Hamana in Japan.
Our experimental results may offer us an useful suggestion as to further investigation of the movements and a food cycle of IPA and AA in marine organisms, such as tuna and oceanic bonito as a migratory fish and plankton, which live at the sea area of Micronesia.

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2-Methoxy-2, 4-diphenyl-3(2H)-furanone (MDPF), a fluorogenic reagent for amino cornpounds, has been evaluated as a precolumn fluorescence derivatization reagent for amino acids. The derivatization reaction was optimized by determining the reaction products formed under various conditions. α-Amino acids gave fluorescent MDPF derivatives which were directly determinable with a flow injection technique. On the other hand, N-alkyl-α-amino acids yielded nonfluorescent MDPF adducts. The adducts were first subjected to chromatography to remove interfering residual MDPF and its hydrolysis product and finally determined as fluorescent MDPF-2-aminoethanol after on-line postcolumn reaction with 2-aminoethanol. The established conditions involves the reaction of amino acids with 10 mmol·dm^-3 MDPF at pH 10 and 20°C for 40 min. The reaction mixture was separated on a reversed-phase C₁₈ column of TSK LS-410 K with gradient elution using 50 mmol·dm^-3 sodium phosphate buffer (pH 7.0)-methanol system. Although most of α-amino acids gave two fluorescent MDPF derivatives due probably to a pair of diastereomers, they were determined in quantities of 2-5 pmol. The relative standard deviations (n=5) of the method ranged from 2.9 to 5.3% for the analyses of 100 pmol of α-amino acids. Furthermore, in the preliminary examination MDPF was also found to be applicable to the precolumn fluorescence derivatization of peptides. Owing to high detectabilities and extreme chemical stabilities of its derivatives, MDPF seems to be promising as a precolumn fluorescence derivatization reagent for α-amino acids and peptides as well as primary amines.

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Selective binding of antitumor platinum(II) complexes with DNA was studied by means of the enzymatic digestion and high-performance liquid chromatographic techniques. Inspection of the enzymatic digestion products of platinum-modified DNA showed that adjacent guanine bases are the preferred platinum-binding sites in DNA.
Reaction products of d(GpG) with a variety of antitumor platinum complexes were separated by HPLC. When the platinum complexes involving optical isomeric diamine were allowed to react with d(GpG), two peaks appeared in the chromatograms because of formation of diastereoisomers. Reaction of d(GpG) with the platinum complexes inv olving meso-diamine ligand also gave two reaction products because of asymmetric structure of the platinum complex. The optimal conditions for separating these compounds are presented. The enzymatic digestion products of (1, 2-cyclohexanediamine)platinum-modified DNA showed four major peaks in the chromatogram. Two of them are assigned to Pt[(1 R, 2 R)-1, 2-cyclohexanediamine][d(GpG)] and Pt[(1 S, 2 S)-1, 2-cyclohexandiamine][d(GpG)]. The remaining two peaks come from Pt[(1 R, 2 S)-1, 2-cyclohexanediamine][d(GpG)]. These results suggest the binding mode of antitumor platinum complexes involving chiral diamine ligand on DNA.

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The retention behavior of some amino acids in high-performance liquid chromatography (HPLC) has been investigated using modified hydrophilic gel beads (PW) such as ACD-PW and Me-ACD-PW. The ACD-PW has 6-deoxy-6-amino-β-cyclodextrin moieties and the Me-ACD-PW has O-methylated amino-β-cyclodextrin moieties. These modified gel beads have both ionic sites (amino moiety on C-6 position of the glucose ring of CD) and hydrophobic cavities. In this paper, the ionic interaction effects between amino moiety on CD ring and guest molecule and the inclusion effects caused by the hydrophobic cavity of CD were examined in the present HPLC systems.
Aromatic amino acids showed low capacity factors because of ionic repulsive force between the amino moiety of amino acid and the amino moiety on CD ring. For the natural aromatic amino acid such as phenylalanine (Phe), tyrosine (Tyr) and dihydroxyphenylalanine (DOPA), the inclusion effect was not observed. But N-substituted amino acids showed high capacity factors; N-acetylated Phe(Ac-Phe) and N-formylated Phe (f-Phe) gave 6and 10 times higher capacity factors than Phe in ACD-PW respectively, and 30 and 50 times higher in Me-ACD-PW. These N-substitution effects on retention behavior were also observed for a nonaromatic amino acid such as alanine (Ala). The capacity factors of N-substituted amino acids depended on the ionic strength of eluent. The dependency was observed clearly in Me-ACD-PW. Methylation of hydroxyl groups on the CD ring enhanced the interaction with amino acids.
The inclusion effect was observed clearly in Me-ACD-PW gel. The aromatic guests such as benzyloxycarbonyl(Z)-Phe and Z-Ala showed high capacity factors. And the aro matic and ionic amino acids such as f-Phe and Ac-Phe gave 10 times higher capacity factors than those in ACD-PW.
These results suggest that the inclusion site and ionic site in CD molecule recognized the target amino acids cooperatively: when both sites stood at intervals, only the inclusion effect was observed. Modified CD has great possibilities to separate many bioactive molecule s as stationary phase in “host-guest chromatography with maltiplex recognition”.

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Determination of catecholamines in human urine was tried by ion-exchange chromatography on a weakly acidic ion exchanger with hydrophilic matrix (Asahipak ES-502 C, 0.76 mm i. d. × 10 cm) using Buffer A (pH 6.7, sodium succinate-borate-e thylenediaminetetraacetate 0.05mol⋅dm^-3- 0.015mol⋅dm^-3- 0.5 mol⋅dm^-3) or Buffer B (pH 6.7, sodium succinate-ethylenediaminetetraacetate 0.04 mol⋅dm^-3- 0.5 mol⋅dm^-3) as the mobile phase at 55°C, or 30°C (Buffer A) or 70°C (Buffer B). Elution with Buffer A at 30°C gave the best separation and diluted urine samples could be analyzed without prepurification. The results agreed well with those obtained by the method using internal standard.

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Separation of oligodeoxyribonucleotides, prepared by chemical synthesis, was carried out using reversed 'phase ion-pair chromatography with LiChrospher 100 RP-18e. By this technique, the peak shape and the separation of peaks were highly improved, compared to the results obtained by conventional reversed phase chromatography with the same column. The chain length and the concentration of the tetraalkylammonium ion-pair reagents were found to be responsible for their retention behaviors and tetrabutylammonium phosphate showed marked enhancement of the peak resolution. In the separation with this reagent, a good linear relationship between the elution volumes and the base numbers of oligodeoxyribonucleotides was obtained. This implies that ion-pair chromatography can be used for the separation of oligodeoxyribonucleotides according to their base numbers.

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The effectiveness of column-switching technique in photometric ion chromatography was investigated by use of two columns, into which resins with different specific ion-exchange capacity were packed. A system is consisted of two pumps, a sample injector, two columns, a switching valve, two UV detectors and a dual-pen recorder. As a result, it was found that the column-switching technique possessed the following advantages: (1)rapid and simultaneous determination pf, yarious ions with noticeably different capacity ratios; (2) excellent separation of the peak which can not be resolved by use of a single column; (3) elimination of system peak.

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