Tadao Sakai

Raman Spectrum of Ultrafine Anatase Powders Derived from Hydrolysis of Alkoxide

Ultrafine, nanometer-sized anatase particles were prepared by the hydrolysis of titanium isopropoxide. Their Raman spectra are discussed in view of the finite size effects. The crystallite size D estimated by the X-ray diffraction peaks (Scherrer method) was found to be correlated with the Raman peak width Γ. The relationship could be expressed in the empirical equation, Γ = Γ0 + kD−α with the scaling exponent α of 1.5. Because the anatase crystal spans a three-dimensional network, the result demonstrates that 2× α is equal to the dimensionality of the sample. In addition, the anatase powders prepared by different hydrolysis schemes regressed into curves with different constant terms γ0 and k. The amount of organic residue was mainly affected by the hydrolysis scheme, and the organic residue caused the formation of defects in the crystalline particle by the following heat treatment. Therefore, it is obvious that the variation in Γ0 and k has a close relation to the defect density of the crystalline particles. The defect densities were estimated by using the correlation between the X-ray diffraction and the Raman data.

Formation of ternary ion associates using diprotic acid dyes and its application to determination of cationic surfactants

A sensitive and selective method is described for the determination of cationic surfactants, such as benzethonium, benzalkonium, cetylpyridinium and trimethylstearylammonium, based on the formation and extraction of ternary ion associates with an acid dye (bromophenol blue or bromochlorophenol blue) and quinidine. Quinidine reacts with divalent anionic dyestuffs to form a bulky 1∶1 complex anion, which is extractable into 1,2-dichloroethane as ternary ion associates with cationic surfactants in nearly neutral media. The ternary ion associate gives a blue product. Linearity of the calibration curve is improved and the extractability of the cationic surfactants is enhanced in the presence of quinidine. In addition, many other amines do not interfere with the determination. The blue ion associates can be used for the selective and sensitive spectrophotometric determination of cationic surfactants.

Simultaneous two- and three-component determinations in multicomponent mixtures by extraction-spectrophotometry and thermochromism of ion-association complexes.

A selective method of determination of amines and quaternary ammonium salts by solvent extraction and thermochromism of ion-association complexes has been established. The method is based on the formation of ion-association species with tetrabromophenolphthalein ethyl ester and the thermochromism effect in the organic phase at low temperature. The absorbance of the red amine charge-transfer complexes decreases quantitatively (DeltaA) with increase in temperature (DeltaT), and Delta A Delta T is characteristic of a particular species. This characteristic has been applied for the sensitive and selective determination of amines. The absorbance of the blue quaternary ammonium ion-association complexes does not vary with temperature, however, and the quaternary ammonium compounds can be determined without interference by amines because of the disappearance of the red species at 60 degrees . Methylephedrine, diphenhydramine, ephedrine (amines), benzethonium and/or berberine (quaternary ammonium compounds) in two- and three-component mixtures can be determined by using the thermochromism effect. The method is highly selective, sensitive and reproducible.

Flow-injection spectrophotometric determination of palladium in catalysts and dental alloys with 2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulfopropyl-amino)aniline

2-(5-Bromo-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)aniline rapidly forms a water-soluble complex with palladium in an acetate-buffered medium at pH 3.2.The molar absorptivity of the complex is 9.84×104l mol−1 at 612 nm. The calibration graph is linear over the range of 10–100 μg l−1 palladium; the detection limit is 2 μg l−1 and the relative standard deviation is 0.6% for 100 μg l−1 palladium. The sample throughput is 50 h−1. Divalent transition metals (Fe, Ni, Co) do not interfere at levels from 2 to 10 mg l−1. Interference from copper is prevented by adding 10−3 M EDTA solution to the carrier stream. Palladium in solutions of catalysts and dental alloys can be determined selectively, sensitively and rapidly.

Double-membrane phase separator for liquid-liquid extraction in flow-injection analysis

Abstract A double-membrane phase separator for liquid-liquid extraction in flow-injection analysis was designed and its usefulness was examined in order to achieve smooth, long-term and efficient phase separation with good reproducibility. The construction and performance of the flow-injection system using the phase separator were illustrated by the extraction of berberine-perchlorate ion associates.

Batchwise and flow-injection methods for thermo-spectrophotometric determination of acetylcholine and choline with tetrabromophenolphthalein ethyl ester

Abstract A selective spectrophotometric method was established for the determination of acetylcholine (Ach) and choline (Ch) by liquid—liquid and thermochromism of ion association complexes. This method is based on the formation of ion association compounds with tetrabromophenolphthalein ethyl ester (TBPE · H) and thermocromism of ion associates in the organic phase, where selectivity can be improved. The absorbance of blue Ach and/or Ch ion association complexes does not vary with temperature changes, but that of the red amine complexes disappears when the temperature of the absorbance measurements is kept at 45°C. A two-line manifold was constructed for the flow-injection method. The sample is injected into the buffered stream adjusted to pH 11 and mixed with the extracting TBPE · H dichloroethane solution. The organic phase separated with a polytetrafluoroethylene porous membrane passes through a temperature-controlled micro flow cell (45°C) and the absorbance of the organic phase is measured. The sample throughputs were 36 h −1 for both Ach and Ch. The calibration graphs were linear in the range 6.25 × 10 −5 –7.5 × 10 −6 mol dm −3 for Ach and 1.25 × 10 −6 –1.5 × 10 −5 mol dm −3 for Ch. The relative standard deviation was 1.2% for 5 × 10 −6 mol dm −3 Ach ( n = 5_ and 1.2% for 1 × 10 −5 mol dm −3 Ch ( n = 8).

Extraction-spectrophotometric determination of nickel in steels and aluminium metal with 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine and ethyl tetrabromophenolphthalein

Abstract Nickel ions react with 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine in aqueous solution at pH 6.8 to form a red 1:3 complex cation which can be extracted at pH 6.3 into 1,2-dichloroethane with ethyl tetrabromophenolphthalein anion as an ion association compound having an absorption maximum at 610 nm. The apparent molar absorptivity is 2.21 × 10 5 l mol −1 cm −1 and a linear calibration graph is obtained in the range 0–0.05 μg ml −1 (0−8.52 × 10 −7 M) nickel in aqueous solution. The r.s.d, is 1.5%. This method can be applied to the determination of traces of nickel in steels and aluminium chips.

Liquid-liquid extraction of cinchona alkaloids by using some metal complexes of optically pure usnic acids

Abstract Liquid-liquid extraction of cinchona alkaloids by using some metal complexes of zinc(II), cobalt(II) and copper(II) with (+)- and (−)-usnic acids was studied. The synergic effect of the chelates was studied by adduct formation with neutral Lewis bases such as tri- n -octylphosphine oxide and optically active isomers of cinchona alkaloids. It was possible to differentiate between the adduct formation of quinine and that of quinidine, and also of cinchonine and of cinchonidine, in the synergic extraction of zinc(II) and cobalt(II) with (+)- and (−)-usnic acids.

Extraction-spectrophotometric determination of trace iron (II) in sea water with 2-[2-(3,5-dibromopyridyl)azo]-5-diethylaminobenzoic acid

An extraction-spectrophotometric method is described for the determination of traces of iron(II) with 2-[2-(3,5-dibromopyridyl)azo]-5-diethyl-aminobenzoic acid. The reagent forms a stable and blue 1∶2 iron/reagent complex that can be extracted into chloroform. The apparent molar absorptivity of the iron(II) complex is 1.09 × 105 1 mol−1 cm−1 at 624 nm in chloroform. The reagent is relatively selective; interferences from cobalt, copper, nickel and vanadium can be removed by using dimethylglyoxime and EDTA. The method is applied to the determination of iron (II) in sea water and aluminium alloys with good precision and accuracy.

Stereoselective adduct formation of α-acylcamphorato-copper(II) chelates with some chiral Lewis bases

The formation constants of the mono-adducts of α-acylcamphorato-copper(II) chelates such as (+)-Cu(facam)2, (−)-Cu(facam)2, (+)-Cu(hfbc)2 and (−)-Cu(hfbc)2 with some chiral Lewis bases were determined spectrophotometrically in benzene. In order to compare the adduct formation constants obtained with the (+)- and (−)-forms, some pairs of chiral Lewis bases such as 1-amino-2-propanol [(R)(−), (S)(+)], 1-(α-naphthyl)ethylamine [(R)(+), (S)(−)], α-phenyl ethylamine [(R)(+), (S)(−)] and also quinine and quinidine were examined as neutral ligands. Although not very pronounced, the effects of combinations obtained for (+)- or (−)-Cu(II) chelates and (+)- or (−)-ligands indicate that formation constants obtained by the formation of adducts with the ligands having different directions of the optical rotation seems to be superior to those with the same direction.