Kunihiko Akatsuka

Preparation of Amberlite XAD resins coated with dithiosemicarbazone compounds and preconcentration of some metal ions

The Amberlite XAD resins coated with dithiosemicarbazones were prepared and their collection behavior of metal ions from aqueous solution was investigated. Among the resins used, the reagent-loaded Amberlite XAD-7 was found to be superior for the collection of metal ions to other reagent-loaded resins used. The quantitative collection of mercury(II), palladium(II) and copper(II) was obtained from acidic medium, while cadmium(II) and lead(II) was obtained from neutral medium by the Amberlite XAD-7 resin coated with dimethylglyoxal bis(4-phenyl-3-thiosemicarbazone) (DMBS). These metal ions collected on the resin were easily eluted with a small volume of N,N-dimethylformamide as their DMBS chelates. This collection-elution method was applied to the determination of their metal ions by reversed-phase high performance liquid chromatography with a spectrophotometric detection.

The spectrophotometric determination of trace molybdenum (VI) after collection and elution as molybdate ion on protonated chitin

Collection and elution method for inorganic anion on protonated chitin has been applied to the spectrophotometric determination of molybdenum (VI). The molybdenum (VI) is collected as molybdate ion on a column of chitin in weak acidic medium which is easily eluted with a small volume of 0.1 M ammonia buffer solution (pH 10). The molybdenum (VI) in the eluent is determined by bromopyrogallol red-Zephiramine method spectrophotometrically. Beers law is obeyed over the concentration range of 0.1-0.8 mug of molybdenum (VI) in 1 ml of eluent at 634 nm. The apparent molar absorptivity is 6x10(4) dm(3) mol(-1) cm(-1). The tolerance limits for WO(4)(2-), VO(3)(-), CrO(4)(2-) and Fe (III) is low, that is, 1-100 times that of molybdenum (VI), but some metal ions and common inorganic anions do not interfere in concentration range of 1000-5000 times that of molybdenum (VI). The present method can be applied to the determination of molybdenum (VI) in natural water samples.

The simple and rapid spectrophotometric determination of trace chromium(VI) after preconcentration as its colored complex on chitin

Preconcentration method with collection of metal complexes on a chitin has been applied to the spectrophotometric determination of chromium(VI) in water. The chromium(VI) is collected as its 1,5-diphenylcarbazide(DPC) complex on a column of chitin in the presence of dodecyl sulfate as counter-ion. The Cr-DPC complex retained on the chitin is eluted with a methanol-1 M acetic acid mixture (7:3, v/v), and the absorbance of the eluent is measured at 541 nm. Beers law is obeyed over the concentration range of 0.05-0.6 mug of chromium(VI) in 1 ml of the eluent. The apparent molar absorptivity is 3.5x10(4) dm(3) mol(-1) cm(-1). The tolerance limits for Fe(III) is low, i.e. ten times that of chromium(VI), but some metal ions and common inorganic anions do not interfere in concentration range of 100-10 000 times that of chromium(VI). The present method can be applied to the determination of chromium(VI) in natural water samples.

Simultaneous determination of platinum(II) and palladium(II) by reversed phase high-performance liquid chromatography with spectrophotometric detection after collection on and elution from resin coated with dimethylglyoxal bis(4-phenyl-3-thisomicarbazone).

Amberlite XAD-7 resin coated with dimethylglyoxal bis(4-phenyl-3-thiosemicarbazone) (DMBS) was prepared and applied to the preconcentration of platinum(II) and palladium(II) from aqueous solution. Platinum(II) and palladium(II) were collected quantitatively on resin coated with the reagent (DMBS-XAD-7) from acidic solution in the presence of iodide ion by a bach method. The metal ions were then easily eluted from DMBS-XAD-7 as their DMBS chelates with a small volume of N,N-dimethylformamide. This collection and elution method was applied to the simultaneous determination of platinum(II) and palladium(II) by reversed-phase high-performance liquid chromatography with spectrophotometric detection using an ODS column and acetone-water as the mobile phase. The proposed method was applied to the determination of the metals in commercially available samples.

Determination of vitamin B12 as cobalt by electrothermal atomic absorption spectrometry using the solid sampling technique

SummaryAn investigation has been carried out to establish a rapid method for the determination of vitamin B12 as cobalt in solid pharmaceutical samples by electrothermal atomization atomic absorption spectrometry with the solid sampling technique using an inner miniature cup. Calibration graphs of peak area versus mass of the element were constructed by use of a synthetic reference material (SyRM). The SyRM is prepared by coprecipitation of cobalt ions with magnesium(II) 8-quinolinate. In order to determine the accuracy of the proposed method, three pharmaceutical preparations were analyzed according to the proposed method using standardization against the SyRM and the results obtained compared with those when solutions of the same samples were analyzed by other techniques. There is good agreement between the results obtained from the proposed and the other method. The detection limit for cobalt in a solid pharmaceutical preparation is 0.15 ng/mg (i.e. 4 ng/mg of vitamin B12) for a typical sample mass of 1.0 mg.

Voltammetric detection of silver(I) using a carbon paste electrode modified with keratin

The voltammetric detection of silver(I) was carried out at a carbon paste electrode (CPE) modified with keratin. Silver(I) was selectively accumulated on the electrode on the basis of its interaction with the thiol and disulfide groups of keratin in 0.1 mol dm–3 acetate buffer (pH 6.7) + 0.1 mol dm–3 NaClO4. After reduction of silver(I) had been carried out, the reoxidation wave of silver(0) appeared at 0.14 V (versus Ag/AgCl) on scanning the potential in the positive direction in 0.1 mol dm–3 acetate buffer (pH 6.7). The detection limit of silver(I) was 2 × 10–8 mol dm–3 when the accumulation time was 10 min. Interference from co-existing substances was slight in the voltammetric measurement because of the interaction with sulfur atoms and the exchange of the medium. The proposed method was applied to the determination of silver(I) in a photographic developer.

Direct determination of trace amounts of arsenic in powdered biological samples by atomic absorption spectrometry using an inner miniature cup for solid sampling techniques

ZusammenfassungZur direkten Arsenbestimmung in NBS und NIES-Referenzmaterialien sowie Meeresorganismen durch AAS wurde ein in einen entsprechenden Ofen einsetzbarer Minaturbecher verwendet. Als Matrixmodifikator wurde ein Gemisch von 3 M Schwefel- und 4 M Salpetersäure mit 60 μg Ni benutzt. Die optimalen Bedingungen wurden durch detaillierte Untersuchungen gefunden. Empfindlichkeit und Genauigkeit des Verfahrens wurden mit der Methode der Arsinerzeugung mit nachfolgender AAS oder ICP-AES verglichen. Relative Standardabweichungen von 3–10% für 7–15 ppm As wurden gefunden.SummaryA new easy solid sampling technique with atomic absorption spectrometry by using an inner miniature cup in conjunction with the cupped type furnace was proposed for the direct determination of arsenic in NBS, NIES standard materials and marine organisms. A mixture of 3 M sulfuric and 4 M nitric acid solution containing 60 μg of nickel was successfully used as the matrix modifier for the powdered samples examined. Optimum experimental conditions were determined based upon detailed examinations for the trace amount determination of arsenic in these samples. Analytical sensitivity and accuracy of this method were compared to the arsine generation followed by atomic absorption or ICP emission spectrometry. The standard deviations for 7–15 ppm As were found to be 3–10%.

Accumulation voltammetry of avidin and biotin using a biotin labeled with Nile Blue A

Abstract Avidin and biotin were detected in accordance with an electrochemical procedure using labeling. Biotin labeled with Nile Blue A, an electroactive dye, was prepared and used in avidin-biotin assay. The binding of the biotin part with avidin makes labeled biotin (LB-N) electroinactive. This is because the part of Nile Blue A is also taken in biotin sites of avidin. Therefore, the concentration of avidin could be estimated by measuring the peak current of LB-N. When biotin and LB-N competed for the site of avidin, biotin was also determined by the changing of the electrode response. Levels of detection for avidin and biotin were 10 −9 M. This method has merit that does not require a separation procedure of the free LB-N from the bound one. On the contrary, an effect for length of spacer between Nile Blue A and the biotin part was investigated. It was shown that adsorption of reagent to the electrode increased with increasing the length of the spacer.

Direct analysis of solid samples by atomic absorption spectrometry, following preconcentration of trace elements from seawater with 8-hydroxyquinoline

Summary8-Hydroxyquinoline (8-HOQ) was used for the preconcentration of Cd, Cu, Mn, Pb and Zn from seawater prior to their determination by graphite furnace atomic absorption spectrometry using an inner miniature cup for solid sampling technique. The metal ions in seawater were precipitated quantitatively in the pH range 7–8.5 with 8-HOQ alone. The precipitate thus formed was directly analysed by an atomic absorption spectrometer equipped with a specially deviced graphite furnace and miniature cup. The present method was confirmed to be highly reliable for analysis of seawater. Detection limits (3δb) for Cd(II), Cu(II), Mn(II), Pb(II) and Zn(II) are 1.4, 10, 5, 10, and 6 ng l−1, respectively, for the analysis of a 400-ml portion of seawater samples. Corresponding precision of 6–14% is typical for determination 5-fold above the detection limits.

Determination of trace elements in sea-water by inductively coupled plasma mass spectrometry after preconcentration by formation of water-soluble complexes and their adsorption onC18-bonded silica gel

A simple and reliable preconcentration method was developed for the determination of seven trace metals (Mn, Fe, Ni, Cu, Zn, Cd and Pb) in sea-water by ICP-MS. The method is based on the formation of water-soluble complexes in an aqueous sample followed by adsorption of the complexes onto a C18-bonded silica gel column. The chelating reagent used was 2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)phenol (5-Br-PAPS). By passage of 100 ml of sea-water sample, after addition of 5-Br-PAPS and adjustment of the pH to 8.3, quantitative adsorption of the metal complexes onto the column took place while the major matrix ions in sea-water passed through the column. A similar but separate sample work-up at pH 4.5 provided acceptably low blank values for Fe. The metals were subsequently eluted with 4.0 ml of 1.0 M HNO3. All seven elements were determined with an all-argon plasma, whereas ultratrace levels of Fe were determined with a nitrogen–argon mixed-gas plasma to reduce the isobaric interference by 40Ar16O on 56Fe. The detection limits of the method, based on a 25-fold preconcentration, range from 0.08 ng l–1 for Cd to 16 ng l–1 for Fe. The precision and accuracy of the method were demonstrated by analyzing coastal and open-ocean sea-water certified reference materials.