Motoshi Nakamura

Separation behaviour of silica-containing mixed oxides as column packing materials for liquid chromatography

Abstract Four kinds of silica—containing mixed oxide gels (silica—zirconia, silica—alumina, silica—titania and silica—magnesia) were prepared by a coprecipitation method and studied as column packing materials for liquid chromatography. The physico-chemical characteristics of the gels such as the BET surface area and the acidity of the solid surface were determined. Further, the separation properties of these gels for benzene, dimethyl phthalate and pyridine were evaluated. It was found that silica—magnesia had the best separation ability for the basic compound pyridine, presumably owing to the decrease in the activity of the silanol group and the existence of only very weak acid sites on the surface.

Resorcinol as Fluorimetric Reagent for the Determination of Nitrate

Abstract Sensitive fluorometric procedure has been developed for the determination of nitrate with resorcinol. Reaction conditions, sensitivity of the method and the effect of nitrite are discussed. It is possible to determine 5 to 70 ng of nitrate-nitrogen by the recommended method.

Conditions for solid-phase extraction of agricultural chemicals in waters by using n-octanol–water partition coefficients

The solid-phase extraction behaviour of 25 aromatic compounds and 20 agricultural chemicals was investigated in a reversed-phase system using eight Sep-Pak cartridges. The recovery was related closely to their n-octanol–water partition coefficients. Those compounds with high coefficients were easily sorbed, but were difficult to elute. The extent of elution could be improved by adding methanol to the sample solution. The results suggest that the most important solid-phase extraction conditions for enrichment and separation can be selected approximately by using the partition coefficient as a key parameter. The influences of humic acid and surfactants on the recovery were also studied. Suggested guidelines for efficient enrichment and separation by solid-phase extraction are presented. Some applications were tested and good results were obtained.

Preparation and evaluation of magnesia-coated silica as column packing material for high-performance liquid chromatography

Abstract The preparation of a mixed oxide gel composed of silica and magnesia was attempted by a coating method in order to develop a useful column packing material for liquid chromatography. The physical properties of the gels obtained remained almost the same as those of the native silica gel, but the surface silanol groups and the acid strength both changed, depending on the preparation conditions. The chromatographic behaviour of the gels was tested using benzene, dimethyl phthalate, pyridine and phenol as solutes. The magnesia-coated silicas calcined at temperatures between 600 and 800°C exhibited the excellent separation abilities for these compounds.

Kinetic studies on thiolato-ligand substitution reactions with halide ions of square-planar palladium(II) complex with bis(2-(diphenylphosphino)ethyl)phenylphosphine

Abstract The square-planar thiolato palladium(II) complex with a terdentate phosphine bound ligand, [Pd(pt)(p3)](BF4) (p3=bis(2-(diphenylphosphino)ethyl)phenylphosphine, pt=1-propanethiolate) has been synthesized and characterized by 31P NMR spectroscopy. The solid state structure of [PdI(p3)]I was determined by an X-ray crystal structure analysis. The kinetic parameters for the thiolato-ligand substitution reactions with halide ions, [Pd(pt)(p3)]++X−→[PdX(p3)]++pt− (X−=Cl−, Br−, I−), in chloroform were obtained as follows: k298=7.22, 1.68 and 10.1×10−4 s−1, ΔH‡=67±2, 56±2 and 63±3 kJ mol−1 and ΔS‡=−80±7, −128±6 and −92±11 J mol−1 K−1, respectively. These kinetic results are compared with those for the corresponding reactions of the trigonal-bipyramidal complex with an analogous phosphine bound ligand, [Pd(pt)(pp3)](BF4) (pp3=tris(2-(diphenylphosphino)ethyl)phosphine).

Adsorption characteristics of organic dyes in aqueous solutions on mixed-oxide gels

SummaryFive alumina-containing gels were investigated on the adsorption characteristics for four types of organic dyes (acidic, basic, reactive, and direct dyes). Alumina-magnesias exhibited the properties as strong solid bases and adsorbed effectively three dyes except for the acidic dye. While, alumina-silicas, strong solid acids, showed the high ability only for the acidic dye.

Spectrophotometric Determination of Nitrite in Wastewater with 4,5-Dihydroxycoumarin

Abstract A rapid and simple spectrophotometric method was developed for the determination of nitrite in wastewater. The procedure was based on the extraction of nitrite with ethyl acetate solution of 4,5-dihydroxycoumarin. Beers law obeyed up to 0.75 ppm of nitrite-nitrogen. Results obtained by using the proposed method on waste-water samples agreed well with those obtained by the diazotising-coupling method.

Adsorption Characteristics of Organic Dyes In Aqueous Solutions On Mixed-Oxide Gels. Silica-Containing Mixed-Oxide Gels

Abstract Adsorption characteristics of four types of organic dyes in aqueous solutions on seven silica-containing mixed-oxide gels were investigated. C.I. Basic Red 18 was adsorbed well on all the gels. Silica-magnesia, which was prepared by the homogeneous precipitation, showed higher adsorptive ability for all the dyes than the other adsorbents. It was proved from the examinations that the initial pH of dye solution, the composition of gel, and the precipitation method of gels affected the adsorptive ability.

Fluorometric determination of tin(IV) with 3-hydroxychromone

Summary3-Hydroxychromone reacts with tin(IV) to produce 1∶1 complex in a weakly acidic-neutral medium. The complex exhibits intense fluorescence. A sensitive method is described for the fluorometric determination of tin(IV) with 3-hydroxychromone. The calibration graph is linear in the range of 0.4–8.0μg/25 ml of tin(IV) (pH 4.5–5.0, Excitation wavelength: 365 nm, Measured total fluorescence). Chloride which generally decreases the fluorescence intensity in the fluorometric determination of tin can be tolerated at 300-mg level.Zusammenfassung3-Hydroxychromon reagiert mit Zinn(IV) in schwach saurem bis neutralem Medium unter Bildung eines 1∶1-Komplexes. Dieser fluoresziert intensiv. Ein empfindliches Verfahren zur Bestimmung von Sn(IV) auf dieser Grundlage wurde ausgearbeitet. Die Eichkurve verläuft in dem Gebiet zwischen 0,4 und 8,0μg Sn/25 ml bei pH 4,5, einer Wellenlänge von 365 nm und bei Messung der Gesamtfluoreszenz geradlinig. Chloride, die die Fluoreszenzintensität bei Zinnbestimmungen im allgemeinen herabsetzen, können bis zu 300 mg toleriert werden.

Complexation reaction of organotins with 3-hydroxyflavone and its application to their fluorometric determination.

モノフェニルスズ(MPT),ジメチルスズ(DMT),ジブチルスズ(DBT),ジフェニルスズ(DPT),トリメチルスズ(TMT),トリブチルスズ(TBT)及びトリフェニルスズ(TPT)と3-ヒドロキシフラボンとの蛍光性錯体生成反応の平衡と速度を検討し,その結果を有機スズの蛍光定量に応用した.錯体の生成速度は有機置換基の数と種類にはほとんど依存しなかったが,錯体の安定性には,フェニルスズについてはMPT>DPT≫TPT,二置換有機スズについてはDPT>DBT>DMTの差が見られたので,この差を有機スズの蛍光定量に利用した.各々の有機スズの定量においては,検出限界10nMで5μMまでのMPT,検出限界20nMで3μMまでのDMT,検出限界20nMで4μMまでのDBT,検出限界30nMで3μMまでのDPTの定量が可能であった.いずれの一置換及び二置換有機スズの定量においても三置換有機スズの共存許容量は相対的に大きく,TMTについては100倍モル以上の共存が許容された.