BUNSEKI KAGAKU Abstracts

The trace analysis of cadmium in rice was carried out by using L-shell excitation of X-ray fluorescence analysis. To reduce the influence of co-existing potassium, the excitation X-ray energy was selected below the absorption edge of potassium. It was found that the remaining background was from resonant inelastic X-ray scattering (RIXS) from potassium. The excitation X-ray energy dependence of the RIXS spectra from KCl was measured, and the optimized X-ray energy was 3580 eV. Optimization of the sample support was also investigated, and the rice flour was fixed onto a film of 6 μm thick polypropylene with polyvinyl acetate. The detection limit of cadmium in rice was 0.34 ppm under the optimized condition.

A spectrophotometric method was established for the determination of manganese(II) {Mn(II)} and Polylysine (PolyL) with o-sulfophenylfluorone (SPF). Beer’s law was obeyed in the range of 0.06〜3.3 μg for Mn(II) in a basic medium with an apparent molar absorptivity(ε) at 565 nm, the relative standard deviation (RSD) being 1.63 × 10⁵ L mol⁻¹ cm⁻¹ and 1.46% (n = 5). This method is about 2-70 times more sensitive than the existing spectrophptpmetric methods, and can determine more easily. Also, the method was successfully applied to assays of Mn(II) in real samples. The thermodynamic parameters suggest that the colored complex formed in this reaction system is an association complex between [Mn(II)−SPF] and [TSAC]. Next, Beer’s law was obeyed in the range of 1.0〜60 μg for PolyL, a basic solution. The ε and RSD are 4.18 × 10⁶ L mol⁻¹ cm⁻¹ (molar weight≒225000) at 565 nm and 1.49% (n = 5), respectively. This method can determine polymers, not monomers. Furthermore, this method was applied to recovery tests of PolyL in real samples ; the results were satisfactory.

A fundamental investigation of the solid phase extraction of arsenic has been conducted using an iron(III)-supported chelate resin immobilizing carboxymethylated pentaethylenehexamine. The amount of arsenic(V) adsorbed on the resin reached the maximum value at pH 4 - 6. Arsenic(III) was scarcely adsorbed ; however, it could be collected on the resin after the oxidation of arsenic(III) to arsenic(V) using a sodium hypochlorite solution. The adsorbed arsenic(V) could be eluted using a sodium hydroxide solution, and was then determined by inductively coupled plasma atomic emission spectrometry. The amount of arsenic(III) could be calculated by subtracting the amount of arsenic(V) from that of both arsenic(III) and arsenic(V), which was obtained using a sodium hypochlorite solution. The proposed method was applicable to the analysis of a certified reference material (Ground Water, ES-H-1).

A hydrophilic interaction-type solid-phase extractant (DAM adsorbent) that was immobilized with a zwitter-ionic macromolecule was applied to the clean-up procedure for the determination of mycotoxin, patulin in apple juices. An apple-juice extract was dissolved by a 1% ethanol - hexane solution, and was then loaded to a solid-phase extraction cartridge packed with 50 mg of a DAM adsorbent. Patulin was adsorbed on the DAM adsorbent trapped quantitatively, and the adsorbed patulin was easily eluted with 2 mL of acetonitrile. An acetonitrile eluate was substituted by 1.0 mL of 0.01% acetic acid aqueous solution prior to quantification by HPLC. No endogeneous compounds interfered with the detection of patulin. The average recovery in the overall procedure of patulin was about 77.0 and 82.1%, with RSDs ranging between 0.9 and 2.6%. The limit of detection was below 1 μg kg⁻¹ for patulin. The proposed clean-up method was applied to the determination of patulin in commercial apple juices and rotten apples, and was detected in apples that had rotted in soil.

In this paper, a novel method is proposed to evaluate the performance of adsorbent material. “Sink efficiency” is used as a parameter to express the performance of an adsorbent placed in a gas flow channel. The sink efficiency varies from 0 (completely inert to the gas) to 1 (perfect sink). Different from conventional dynamic evaluation, the sink efficiency is a parameter that does not depend on the gas flow rate and can be easily obtained from the relationship between the removal efficiency and the gas flow rate, and from a simulation spreadsheet proposed before. The removal efficiency at various flow rate can be obtained from the sink efficiency, and it is valuable to design the removal column device. This method was applied to the removal of hydrogen sulfide by limonite, active carbon and gas adsorptive wall papers. Hydrogen sulfide was flowed through a channel, in which limonite was placed, and passed hydrogen sulfide was absorbed in an alkaline solution to be measured as un-adsorbed gas by flow injection analysis. Sink efficiencies were obtained from a plot of the removal efficiencies against the gas flow rate and the simulation program. According to the experiments, it was found that the limonite surface did not work as a perfect, sink and the sink efficiency decreased after use for the removal of hydrogen sulfide in a biogas generation plant. The performance of gas adsorbing is also discussed from the view point of micro-scale characteristics.

A simple on-site column analysis/solid-phase extraction method for the determination of fluoride in water was developed based on the combining of the analysis using a column collection and solid-phase extraction, followed by spectrophotometric determination. The column was prepared by packing silica gel loaded with a zirconium-alizarine red S complex. In on-site column analysis, the concentration of fluoride was measured by the length of a colored-band (white band) formed in the column, which was made by ligand-exchange reaction between fluoride and alizarine red S bonded with zirconium, when the fluoride in water was collected by the column. After the collected fluoride in the column was easily eluted by elution (sodium hydroxide solution), its spectrophotometric determination was made with good precision. This method was useful for simple on-site determination using simple on-site column analysis, and then a solid-phase extraction method gave precise determination values. The established method was successfully applied to environmental water samples.

Inorganic arsenic [iAs : As(III) and As(V)] concentrations in a certified reference material of total diet matrix (NIES CRM No.27 Typical Japanese Diet, TJD) were determinate by liquid chromatography-ICP mass spectrometry (LC-ICP-MS) with three different LC conditions and with or without a hydride generation system. The iAs were extracted from TJD by a method given in the literature (0.07 mol L⁻¹ HCl + pepsin, 37°C for 2hr). The detection limits for the iAs were better than 6.1 ng As g⁻¹ in TJD (corresponds to 0.92 ng As g⁻¹ on a wet diet sample), indicating sufficient sensitivity for iAs in total diet samples. The reproducibility was 1.8-12.1% and the linearity of the calibration lines was satisfactory. The recovery of added iAs was 101-106%. When the extraction was repeated 3 times, the sum of the concentrations of arsenic species detected by the LC-1 agreed with the certified values for total arsenic in TJD. The total content of As(V) and As(III) was estimated to be 65±2 and 18±2 ng As g⁻¹, respectively, by LC-1 condition. The analytical results of iAs in TJD based on the three LC-ICP-MS conditions by this particular extraction method were consistent with each other and the reference value was estimated to be 43 and 17 ng As g⁻¹ for As(V) and As(III), respectively. The present results will be valuable in the quality control of iAs analysis of total diet samples for iAs risk assessment in Japan.

In order to secure the safety of drinking water in Japan, perchlorate has recently been added to the list of examination regulated items under the Water Supply Law set by the Ministry of Health, Labour and Welfare on April 1, 2009. Accordingly the target value for perchlorate residue in tap water was newly set at 25 μg/L on April 1, 2011. A sensitive analytical method for the residual level of perchlorate in tap water was examined using large-loop injection ion chromatography. The retention time of perchlorate using ion chromatograph was 37.0 min by gradient analysis with potassium hydroxide in the concentration range from 2.5 mM to 40 mM. However, an isocratic run of potassium hydroxide of 65 mM shortened the retention time to 11.0 min. In addition, by increasing the volume of the injection sample from 200 μL to 1000 μL, the limit of determination was lowered from 3.5 μg/L to 0.40 μg/L. Furthermore, 100 mL of a water sample was put into a Teflon beaker and heated using a hot plate to concentrate to 10 mL (10 times). By using the concentrated sample, it was possible to measure a limit of determination of 0.08 μg/L, which is almost equal to 1/300 of the target value of 25 μg/L. An analysis of perchlorate in tap water in Hyogo prefecture was conducted using this method. As a result, the frequency of detection was 42%, and the range of detection was from 0.08 to 0.30 μg/L.

A highly sensitive method for the on-line simultaneous determination of trace Cu^II and Ni^II in high-purity alkaline solutions has been demonstrated by anodic stripping voltammetry (ASV) using a radial flow cell Au electrode (RFCE-Au). In this method, the electrolysis process is performed while alkaline solutions flow through RFCE-Au without any pretreatment. Under the optimum conditions, linear calibration graphs for Cu^II and Ni^II were obtained in the range of 0.5-6.0 μg dm⁻³ in KOH solution and 0.5-5.0 μg dm⁻³ in NaOH solution, respectively. The detection limits of Cu^II and Ni^II, defined as 3 σ of the 0.5 μg dm⁻³ signal, were 0.047 μg dm⁻³ and 0.13 μg dm⁻³ in KOH solution, and 0.058 μg dm⁻³ and 0.15 μg dm⁻³ in NaOH solution, respectively. The proposed method is applicable to on-line trace analysis of Cu^II and Ni^II, which has been urgently needed in the semiconductor manufacturing process.

We developed a capillary zone electrophoresis (CZE) method with indirect UV detection for the simultaneous determination of major constituents, such as chloride (expressed as Cl⁻), inorganic phosphate (PO₄³⁻), and citric acid in a human serum. The limits of detection (LODs) for Cl⁻, PO₄³⁻, and citric acid were, respectively, 4.7, 2.0, and 1.3 μmol/L at a signal-to-noise ratio of three. The relative standard deviation (RSD, n = 8) of the peak area obtained for Cl⁻, PO₄³⁻, and citric acid in human serum from a healthy adult without deproteinization were 1.0, 1.6, and 4.0%, respectively. The analytes were detected within 18 min. Dproteinization was not required using a background electrolyte (BGE) containing 0.01% hydroxypropylmethylcellulose (HPMC). The analytical results for Cl⁻ and PO₄³⁻ in serum samples for quality control and human serum samples from healthy adults obtained by the proposed method agreed with those obtained by conventional methods. The proposed procedure could be useful as a simple diagnostic method for patients suffering from some diseases.

A novel sectrophotometric method was established for the determination of tetracycline antibiotics (TC). The method is based on an ion association ternary-complex formation between [TC-gallium(III)] and [Eosin]. Beer’s law is obeyed in the range of 0.5〜5.0 μg/mL. In the determination of minocycline (Mino), the apparent molar absorptivity and the relative standard deviation were 8.63 × 10⁴ L mol⁻¹ cm⁻¹ and 1.64% (n = 8), respectively. The proposed method was successfully applied to assays of Mino in pharmaceutical preparations (tablet, granule, injection); the results were satisfactory. A membrane filter preconcentration (MF) method for the determination of micro amounts of Mino that involves the filtration of an association complex on a membrane filter, followed by its redissolution is described. This MF method is about 180-times more sensitive than the usual spectrophotometry.

The adsorption and desorption of chromium(VI) ion on activated carbons in aqueous solution were studied. Adsorption experiments of Cr(VI) on pretreated activated carbons showed that the pH dependence of adsorption rates can be explained by the difference of the adsorbed species. Also, the reduction rates of Cr(VI) to Cr(III) by activated carbons in acidic solutions were quantitatively determined. In desorption experiments, a high recovery rate (90%) was obtained for activated carbons treated with adsorption at pH = 6 and elution by a 0.1 mol L⁻¹ NaOH solution.

A novel fluorophotometric method was established for the determination of serotonin on the heating in propylene glycol. In the determination of serotonin, the calibration curve exhibited linearity over a serotonin concentration range of 0.05〜2.5 μg/mL at an emission wavelength of 550 nm with an excitation of 474 nm; the relative standard deviation was of 2.4% (n = 5) for 1.0 μg/mL of serotonin. The method was applied to recovery tests of serotonin in goat serum, calf serum, and human urine; the results were satisfactory. The proposed method should be useful for a simple and selective determination of serotonin in real samples.

We studied the wet-ashing condition and found a proper method for the decomposition of organoarsenic without using a closed microwave digestion oven system. The hydride generation technique is incapable of detecting organoarsenic, such as arsenobetaine and arsenocholine without decomposition. However, organoarsenic is hard to be decomposed by the conventional wet-ashing method. Therefore we developed open wet-ashing conditions and found optimized conditions (HNO₃-H₂SO₄-HClO₄ at 400°C or higher without dryness) to completely decompose organoarsenic.