Koichi Oguma

An alternating trilinear decomposition algorithm with application to calibration of HPLC–DAD for simultaneous determination of overlapped chlorinated aromatic hydrocarbons

In this paper an alternating trilinear decomposition (ATLD) algorithm that is an improvement of the traditional PARAFAC algorithm without any constraints is described as an alternative algorithm for decomposition of three‐way data arrays. It is based on an alternating least squares principle and an improved iterative procedure that, in a real trilinear sense, uses the Moore–Penrose generalized inverse with singular value decomposition. Its performance is compared with that of the traditional PARAFAC algorithm by a series of Monte Carlo simulations with different noise levels. It was found that the ATLD algorithm has a capability to converge faster than the traditional PARAFAC algorithm. The ATLD‐based second‐order calibration retains the second‐order advantage that calibration in the presence of unknown interferents can be performed to provide satisfactory concentration estimates. Both algorithms have been used for simultaneous determination of overlapped chlorinated aromatic hydrocarbons measured by means of a high‐performance liquid chromatograph with a diode array detector.

Population Analysis of Structural Properties of Giant Liposomes by Flow Cytometry

We used fluorescence flow cytometry to analyze the structural properties of populations of giant liposomes formed by different preparation methods. The inner aqueous volumes and nominal membrane surface areas of a large number of individual liposomes were measured simultaneously by using fluorescent markers. We compared these properties of liposomes prepared by the natural swelling method, the freeze-dried empty liposomes method, and the water-in-oil (W/O) emulsion method. A two-dimensional contour distribution map of the inner volume and the nominal surface area was used to elucidate the structural properties of liposomes over a wide range of liposome sizes. Lamellarity of liposomes was evaluated as the ratio of the nominal surface area to the theoretical surface area calculated from the liposome inner volume. This population analysis revealed the dependency of lamellarity on liposome volume: while the nominal surface areas of populations of liposomes prepared by the natural swelling and the freeze-dried empty liposome methods were widely distributed, those prepared by the W/O emulsion method had a narrower distribution within small values. Furthermore, with the latter method, the nominal surface area varied in proportion to the two-thirds power of the inner volume ranging for several orders of magnitude, indicating the liposomes had a thin membrane, which was constant for the wide volume range. The results as well as the methodology presented here would be useful in designing giant liposomes with desired properties.

Simultaneous determination of iron(III) and total iron by flow injection analysis using kinetic spectrophotometry with tiron

Two flow injection analysis systems have been developed for the simultaneous spectrophotometric determination of iron(III) and total iron using Tiron as the colour developing reagent. The first system uses a single detector with two flow cells aligned with the same optical path to yield two peaks corresponding to iron(III) and total iron in the sample. The sample through put is high (60 samples h–1) with a precision of 0.35% for iron(III) and 0.55% for total iron. The second system is a multi-detection system which allows 30 samples to be analysed per hour with the advantage of much simpler instrumentation.

Ion interaction chromatography of nitrilotriacetatocomplexes of the rare earth elements with post-column reaction detection.

The chromatographic behaviour of nitrilotriacetatocomplexes of the rare earth elements (Sc, Y and lanthanides) on a reversed phase ODS column has been investigated in the presence of 1-octane-sulphonate. There is a great difference in selectivity for the ODS among the rare earth nitrilotriacetato-complexes. Concentration gradient elution with nitrilotriacetic acid (0.005-0.050M, pH 3.0) that contains 0.01M 1-octanesulphonate allows the rare earth elements to be separated from each other within 30 min at room temperature, except a Gd-Eu pair which is eluted together. Yttrium elutes at about 10 min between samarium and neodymium. Detection and quantitation of the rare earth elements can be achieved by post-column reaction with Chlorophosphonazo III in acid media at 700 nm.

Determination of traces of palladium in stream sediment and auto catalyst by FI-ICP-OES using on-line separation and preconcentration with QuadraSil TA.

A flow injection analysis (FIA) method using on-line separation and preconcentration with a novel metal scavenger beads, QuadraSil TA, has been developed for the ICP-OES determination of traces of palladium. QuadraSil TA contains diethylenetriamine as a functional group on spherical silica beads and shows the highest selectivity for Pd(II) at pH 1 (0.1 mol l(-1) hydrochloric acid) solution. An aliquot of the sample solution prepared as 0.1 mol l(-1) in hydrochloric acid was passed through the QuadraSil TA column. After washing the column with the carrier solution, the Pd(II) retained on the column was eluted with 0.05 mol l(-1) thiourea solution and the eluate was directly introduced into an ICP-OES. The proposed method was successfully applied to the determination of traces of palladium in JSd-2 stream sediment certified reference material [0.019+/-0.001 microg g(-1) (n=3); provisional value: 0.0212 microg g(-1)] and SRM 2556 used auto catalyst certified reference material [315+/-4 microg g(-1) (n=4); certified value: 326 microg g(-1)]. The detection limit (3 sigma) of 0.28 ng ml(-1) was obtained for 5 ml of sample solution. The sample through puts for 5 ml and 100 microl of the sample solutions were 10 and 15 h(-1), respectively.

Separation and determination of quaternary ammonium compounds by high-performance liquid chromatography with a hydrophilic polymer column and conductometric detection

Abstract An HPLC method has been developed for separation and determination of long alkyl chain quaternary ammonium compounds. A column packed with a hydrophilic polymer packing, Shodex Asahipak GF-310 HQ, and a water–acetonitrile mixture containing 4,4′-bipyridyl and hydrochloric acid were used to depress hydrophobic adsorption of the quaternary ammonium compounds and increase the sensitivity of the conductometric detection with a micromembrane suppressor. Dodecyltrimethylammonium, cetyltrimethylammonium, tetradecyldimethylbenzylammonium and stearyltrimethylammonium ions can be completely separated from one another and quantified at 0.1 nmol level.

Aqueous two-phase extraction of nickel dimethylglyoximato complex and its application to spectrophotometric determination of nickel in stainless steel.

A polyethylene glycol (PEG)-based aqueous two-phase system has been established for the extraction of Ni-dimethylglyoximato complex. Appropriate amounts of PEG solution and solid (NH(4))(2)SO(4) were added to the Ni-dimethylglyoximato complex which had been formed in the presence of sodium tartrate and K(2)S(2)O(8) at pH 12 in a separatory funnel and shaken vigorously for about 1min. The mixture was allowed to stand for 10min and then the absorbance of the extracted complex in the upper PEG-rich phase was measured at 470nm. Beers law was obeyed over the range of 0.26-2.1ppm Ni. The proposed extraction method has been applied to the determination of Ni in steel. A steel sample was decomposed with an appropriate acid mixture. An aliquot of the sample solution was taken, treated with H(3)PO(4) and most of the iron and copper were removed by hydroxide precipitation using solid BaCO(3) to control the pH of the sample solution in advance of the extraction of Ni. The analytical results obtained for Ni in steel certified reference material JSS 650-10 (The Japan Iron and Steel Federation), BCS 323 (Bureau of Analysed Samples Ltd.) and NIST SRM 361 and 362 (National Institute of Standards and Technology) were in good agreement with certified values.

Simultaneous determination of trace amounts of iron(III) and titanium(IV) by flow injection with spectrophotometric detection

The simultaneous determination of iron(III) and titanium(IV) has been carried out by flow injection using Tiron as the colour-developing reagent. The sample is injected simultaneously at two inlet points separated by a silver reductor column and the two plugs are allowed to meet the Tiron solution. The coloured slugs reach the detector cell at different times, giving double peaks, and are monitored at 430 nm. The first peak affords the concentration of iron(III) plus titanium(IV) and the second the concentration of titanium(IV). The system allows 30 samples to be analysed per hour for iron(III) and titanium(IV). Results are presented for the quantitative analysis of 11 standard reference rock samples of the Geological Survey of Japan. The average precision (relative standard deviation) is 1.0 and 0.87% for total iron and titanium(IV) in rocks, respectively.

Determination of uranium in seawater by flow-injection preconcentration on dodecylamidoxime-impregnated resin and spectrophotometric detection

A flow injection method has been developed for the determination of uranium in seawater combining the on-line preconcentration with spectrophotometric detection. An aliquot (10 mL) of the seawater sample adjusted to pH 5.5 was injected into the analytical system and uranium was adsorbed on the column packed with styrene-divinylbenzene copolymer resin (Bio-Beads SM-2) modified with dodecylamidoxime which showed high selectivity to uranium. Uranium was then eluted with 0.01 M hydrochloric acid and detected spectrophotometrically after the reaction with Chlorophosphonazo III. Interference from calcium and strontium was masked with cyclohexanediaminetetraacetic acid added to the chromogenic reagent solution. The sample throughput, the detection limit (3σ), and the preconcentration factor were 23 per hour, 0.13 μg/L, and 20, respectively, when the sample injection volume was kept at 10 mL. The precision at the 2 μg/L level was less than 4% (RSD). The proposed method was applied to the determination of uranium in the seawater samples collected off the Boso peninsula, Japan and the uranium concentration was found to be ca. 3 μg/L, which is close to the literature data. The yield of the recovery test ranged from 95% to 99%.

Selective chromatographic separation of uranium(VI) on DEAE-cellulose layers in dilute acetic acid media

Abstract In dilute acetic acid solutions, U(VI) shows a useful chromatographic distribution on DEAE-cellulose layers, while most other metal ions migrate upwards to the solvent front or remain at or near the start. This chromatographic behaviour of U(VI) enables a selective method for the separation of U(VI) by thin-layer chromatography to be developed. The RF values on DEAE-cellulose and Avicel SF are quoted for 34 metal ions as a function of acetic acid concentration in the range 1–6 M. Results for two- and three-component separations by elution with 1 M acetic acid are given in order to illustrate the effectiveness and utility of the present method.