BUNSEKI KAGAKU Abstracts

Direct sampling of deuterium lamp background correction metal furnace atomic absorption spectrometry has been developed for a screening analysis of hazardous metals in plastics. Cr, Cd, Hg and Pb in plastics were analyzed by a direct introduction of solid sampling technique. Usual 3 step heating program were applied for the determination of Cr, Cd and Pb, however, one-step atomization program (400°C, 20 s) was used for the determination of Hg. Weighing mass range were optimized to under 1.0 mg for the determination of hazardous metals to avoid Lorents pressure effect. Calibration curves were drawn with aqueous standard for the determination of Cr, Cd, Pb and with polyester standard for Hg. With the proposed analysis, under 10 times of the determination were effective for screening and over 15 times analysis adoptable for precise analysis for hazardous metals, in plastic samples. The present methods was applied for the determination for Cr, Cd, Hg and Pb in BCR 680, 681 and showed the values agreed well to the reference values with under 6% of relative standard deviation (n＝15).

The chemical compositions of iron ore used for iron making are mainly hematite (Fe₂O₃), magnetite (Fe₃O₄) and goethite (FeOOH). The uranium (U) and thorium (Th) of natural radioactive elements are contained with μg/g or ng/g levels as impurity elements in these iron ores. The purpose of this study was to develop on analytical method for the determination of radioactivities for U and Th isotopes in iron ore by an α spectrometry. The certified reference material of iron ore (JSS-805-1, hematite of BMR iron ore) was used as analytical samples in this work. The concentrations of U (3.4±0.2 μg/g) (²³⁸U radioactivity : 42.0±2.5 mBq/g) and Th (0.35±0.03 μg/g) (²³²Th radioactivity : 1.4±0.1 mBq/g) in the reference material had been determined by an instrumental neutron activation analysis. After the iron ore samples were dissolved by a microwave method, U and Th were separated from the matrix elements by several chemical processes. Chemical processes to remove matrix elements were mainly Fe(OH)₃ coprecipitation, Fe(OH)₃ dissolution, NdF₃ coprecipitation, NdF₃ dissolution, Nd(OH)₃ coprecipitation and Nd(OH)₃ dissolution. After these chemical processes, U and Th were only separated by two steps : anion–exchange chromatography. Further, a Sm(III) carrier as an internal standard was added in the U fraction or the Th fraction, and SmF₃ coprecipitation was performed with a HF solution. These precipitation samples were measured by an α spectrometer system. The Th standard solution was added in the dissolved solution of the iron ore samples. The α peaks of ²³⁸U, ²³⁴U, ²³²Th, ²³⁰Th, ²²⁸Th and ¹⁴⁷Sm were determined from the α spectra of these fraction. ¹⁴⁷Sm as an internal standard is a natural α emitter. As results, the chemical yields of U and Th were 90±6% and 103±2%, respectively. Also, it was found that the relation of the radioactivity of ²³⁸U−²³⁴U was radioactive equilibrium, and that the relation of the radioactivity of ²³⁸U−²³⁰Th was none-radioactive equilibrium.

A simple and rapid analysis of Cr(VI) in river-water samples using a thixotropic gel has been developed. Diphenylcarbazide was dissolved in a thixotropic gel that produces a sol-gel transition upon shaking. Efficient extraction and rapid coloring for Cr(VI) were obtained by using thixotropic gel. A sample water and buffer solution was added into a sample tube with the thixotropic gel, which was shaken for one minute. The Cr(VI) concentration was determined visually and by an absorption photometric analysis, based on the color intensity of colored thixotropic gel. The determinable concentration ranged from 0.03 to 1.00 mgCr/dm³ for the visual measurement and 7.36×10⁻³ to 1.00 mg/dm³ for the absorption photometric analysis. No effect of coexisting ions for Cr(VI) determination was recognized.

By the accident of explosion at a petrochemical plant in Jilin city of China, on November, 13th, 2005, about 100 tons of nitrobenzene, benzene and aniline were spilled into the Songhua river flowing in the north-east area of China. Therefore, nitrobenzene in fish samples collected from the Songhua river in Harbin city after passing of contaminants were determined. A cyclic steam distillation apparatus for extraction and concentration of nitrobenzene in fish samples was used, and the preparation and pretreatment of a fish samples and extraction conditions were investigated. As a result, relatively high concentration of nitrobenzene was found out in fish samples collected in March and October of 2006. Nitrophenol, one of the expected products by metabolism of nitrobenzene in fish samples was also determined. o-, m-, p- nitrophenol were detected in fish samples.

A sensitive adsorptive stripping voltammetry, based on the formation of the complex of boron(III) with 4-[(4-diethylamino-2-hydroxyphenyl)azo]-5-hydroxynaphthalene-2,7-disulfonic acid (Beryllon III) is described for the determination of trace boron in environmental water samples. The complex was accumulated on a hanging mercury-drop electrode at −0.35 V vs. SCE for 60 s under stirring in 0.06 M nitrate−0.04 M sulfate supporting electrolyte (pH 4.5), and was subsequently cathodically stripped to −0.8 V vs. SCE at a scan rate of 10 mV s⁻¹ by using a differential pulse mode. A reduction peak belonging to the adsorbed complex was observed at around −0.4 V vs. SCE in the stripping voltammogram. The influence of foreign elements on the boron determination was evaluated. The interferences of aluminum(III), iron(III) and silicon(IV) were eliminated by adding metaphosphoric acid. The calibration graph {peak height vs. boron(III) concentration} was linear over the concentration range of 0.2〜100 ng mL⁻¹ (correlation coefficient＞0.999), with a relative standard deviation (n＝4) of 2〜7%. The proposed method without using troublesome preconcentration steps was applied to the determination of trace boron in several environmental water samples with good precision and accuracy.

The separation of Ga^III and In^III from Al^III using chelate resin, i.e., Chelex 100, and the elution of Ga^III and In^III from the resin were investigated by a batch-wise method. In the separation of Ga^III and In^III from Al^III, when fluoride ion (NH₄F) as a masking reagent for Al^III was added to the solution with Chelex 100, Ga^III and In^III could be selectively adsorbed to the resin. In the elution of Ga^III and In^III from the resin, when diethylenetriamine-N,N,N',N",N"-pentaacetic acid (DTPA) was added into the solution with Ga^III and In^III adsorbed to Chelex 100, In^III was selectively eluted from the resin. The separation system could also be applied to a consecutive flow method using a column packed with Chelex 100 resin. In addition, the recovery of Ga^III adsorbed from the resin was carried out by 2.0 mol dm⁻³ nitric acid at a flow rate below 0.87 cm³ min⁻¹.

(1) The marine sediment (NMIJ CRM 7302a) was directly decomposed with a mixture of 1 mL of hydrofluoric acid, 1 mL of nitric acid and 8 mL of (1＋1)sulfuric acid in a Teflon sealed vessel at 230°C for 16 h. The total chromium was determined. (2) An indirect acid method after the decomposition of organic materials by H₂SO₄-HNO₃ was compared to a direct acid decomposition method (1). The analytical results of the total-chromium (t-Cr) by methods (1) and (2) coincided with the certified value of the NMIJ CRM 7302a. The direct method of (1) was recommended for a pre-treatment of a marine sediment sample. On the other hand, an electron probe micro-analyzer (EPMA) was applied to an element analysis of the trace precipitation in a direct acid decomposition process in a Teflon-sealed vessel. The white trace precipitation was a crystal of AlF, and the black trace precipitation was carbon. Trace chromium was not detected by the precipitations. How to obtain accurate data from the pre-treatments was discussed regarding the data of this method and other data : that is EPA 3050B, ISO 11466, EPA 3052B, or NAA found from the Union Internationale des Laboratories Indepentants, Inter-Laboratoriy Practice report. The importance of deciding the assigned value was discussed for a statistical evaluation of the data of participants in a proficiency testing. The certified reference materials (CRM) should be furnished by both the sheet decomposition methods of CRM in addition to methods (sheet) for accurate quantitative analyses of the analytes in the CRM.

Calibration curves for copper determination were compared using several copper emission lines, when various dissolution acids were employed for sample preparation in inductively coupled plasma-optical emission spectrometry with a conventional and a hydrofluoric acid-proof torch. The conventional torch was composed of a plasma torch with a central tube made of quartz, a concentric-type nebulizer made of quartz and a cyclone-type spray chamber made of glass. On the other hand the hydrofluoric acid-proof torch was composed of a plasma torch with a central tube made of sapphire, a cross flow-type nebulizer made of platinum and a single-pass Scott-type spray chamber made of polytetrafluoroethylene. When sample solutions including nitric acid or a mixture of nitric acid and hydrofluoric acid were introduced to the ICP plasma through the hydrofluoric acid-proof torch, the emission intensities of the copper lines were observed with small fluctuations, leading to a more precise determination of copper. On the other hand, when sample solutions including sulfuric acid or tartaric acid were introduced into the ICP plasma, the emission intensities became smaller with poor analytical precision, independent of the kind of copper lines employed. The reason for this would be a physical interference caused by variations in the physical properties of each acid solution.

Simultaneous determination of total nitrogen (T-N) and total phosphorus (T-P) in sewage water by flow injection analysis (FIA) have been developed. This analytical method provides high linearity of the calibration curve as well as repeatability and reproducibility. The correlation coefficients of the calibration curve were estimated to be from 0.9989 to 0.9999 for the T-N in the concentration range from 0.2 mg L⁻¹ to 20 mg L⁻¹, and for the T-P in the concentration range from 0.02 mg L⁻¹ to 2 mg L⁻¹. The detection limit calculated on 3σ were 0.186 mg L⁻¹ for T-N, and 0.003 mg L⁻¹ for T-P. This flow injection analysis could be successfully applied to the determination of T-N and T-P in the inlet water and outlet water of sewage water.