BUNSEKI KAGAKU Abstracts

Vol. 52 No. 4

April, 2003

Accounts

Thermoresponsive polymer-mediated preconcentration for trace analysis

Tohru Saitoh¹, Chiyo Matsubara² and Masataka Hiraide¹

(Received 24 December 2002, Accepted 10 February 2003)

Simple and rapid preconcentration techniques using themoresponsive polymers were developed for the determination of traces of organic and inorganic constituents in aqueous solutions. Thermoresponsive polymers, including poly(N-isopropylacrylamide) and poly(vinylmethyl ether), are water-soluble at room temperature, but become sparingly soluble above their critical solution temperatures (ca. 3°C) to form gum-like precipitates. Hydrophobic organic compounds in aqueous solutions were effectively collected on the polymer precipitates, depending on their hydrophobic properties. On the other hand, hydrophilic components remained in the bulk aqueous solutions. Because the polymer phase was highly condensed, the concentrations of analytes were easily increased 100-fold. Hydrated metal ions were converted into hydrophobic chelates with 8-hydroxyquinoline or ammonium pyrrolidine dithiocarbamate, which were successfully incorporated in the polymer phase. Water-soluble charged metal chelates were also concentrated by using adequate counter ions. After dissolving the polymer phase in a small amount of organic solvent, the solution was directly analyzed by HPLC, graphite furnace AAS or ICP-MS. Polymer-mediated preconcentration techniques can also be applicable to the clarification of industrial wastewater.

Keywords : thermoresponsive polymers; preconcentration; hydrophobic compounds; metal ions; metal chelates; water analysis.

Research Papers

Separation and determination of chromium (III) and chromium (VI) in water samples by inductively coupled plasma atomic emission spectrometry after collecting these species on CaHPO₄ powder

Tomohiro Narukawa¹, Yukitoki Morita², Takeshi Otsuka³, Kenneth W. Riley¹ and David H. French¹

(Received 10 October 2002, Accepted 31 January 2003)

A simple method for the separation and determination of chromium (III) and chromium (VI) in water samples using a powder of calcium compounds was examined. It was found that CaO, CaCO₃, CaSO₄ and CaHPO₄ are applicable to the collection of chromium (III) over the range of pH 8 to 13. To a 100 ml sample solution (pH 10) containing less than 0.25 µg of chromium (III) and chromium (VI), 100 mg of CaHPO₄ powder was added, and the mixture was stirred for 10 min by a stirrer. Then, chromium (III) in the sample solution was collected on CaHPO₄ powder. The mixture was separated into CaHPO₄ containing chromium (III) and a liquid phase containing chromium (VI) through a membrane filter by vacuum filtration. The liquid phase containing chromium (VI) was added to 1 g of N₂H₆SO₄ for the reduction to chromium (III). We found that chromium (VI) was reduced 100% to chromium (III) within 3 min by N₂H₆SO₄. Similarly, the chromium (III) that was reduced from chromium (VI) was collected on CaHPO₄ powder. The obtained CaHPO₄ powder samples were dissolved with hydrochloric acid (final concentration, 2 mol l^-1 HCl) and prepared to a constant volume (25 ml). The concentrations of chromium in the obtained solutions were determined by ICP-AES. When this method was used, the detection limits (3σ) from a 500 ml sample solution was 0.3 µg l^-1. The proposed method has been applied to several water samples.

Keywords : ICP-AES; separation and determination of chromium (III) and chromium (VI); reduction of chromium (VI); calcium compound as a collector; water sample.

Method of cluster making for a multivariate analysis

Toshiyuki Mitsui¹, Syuji Okuyama² and Minemasa Hida²

(Received 5 December 2002, Accepted 4 February 2003)

A qualitative analysis involving multivariate analysis does not have a clear standard on which to base the results. Any difference in the qualitative analytical results by individual analysts raises doubt concerning the reliability of the qualitative analysis in which a multivariate analysis is used. The qualitative analysis for identification is evaluated as follows. First, the obtained 5~15 data from measuring one sample is added to unknown cluster belonging to a sample (unknown sample) to identify the difference, and calculated by a principal component analysis for removing the outlier in unknown samples. Next, the cluster analysis is examined. When the Euclid distance of the unknown sample cluster is smaller than that of the data cluster, the unknown sample cluster is judged as one cluster. Next, the relations between the unknown samples are calculated by soft independent modeling of the class analogies method (SIMCA method) based on the result of the cluster analysis. The unknown samples are calculated by a principal component analysis based on the result of the SIMCA method. Finally, the cluster belonging of the individual unknown sample is specified from the result of the cluster analysis and the principal component analysis. The unknown samples are accurately made into a cluster by such a method.

Keywords : cluster-making method; principal component analysis; cluster analysis; KNN method; SIMCA method.

Study of a metal-coated hollow-fiber membrane electrode for sugar detection by an amperometric detection method

Osamu Igarashi¹, Masayuki Uto², Sadanobu Inoue², Suwaru Hoshi², Toshitsugu Sugawara³, Kazuyuki Kimura³, Kenji Misawa³ and Junji Arisawa³

(Received 3 July 2002, Accepted 17 February 2003)

A metal-coated hollow-fiber membrane electrode (MCHE) has been applied as a working electrode of an electrochemical detector in high-performance liquid chromatography. In this paper, the structure of the detector was studied for obtaining a high sensitivity and sharp response on a model of electrochemical oxidation of glucose in an alkaline solution. The MCHE has a tubular structure with an inner volume that broadens the output signal peak with a wide distribution of the specimen concentration due to a residual sodium hydroxide solution. An analysis of the dead volume of the present detector revealed that the volume of holes in the membrane wall was almost equal to the inner volume of the electrode. Only the inside metal layer of the MCHE was made active for electrochemical detection in order to reduce the effect of the dead volume of the membrane holes. The detection limit and the half-width of the peak were down to 0.69 pmol and 1.8 s, respectively.

Keywords : metal coated hollow fiber membrane electrode; HPLC; elctrochemical detector; amperometric detector; sugar sensor.

Technical Papers

Simplified determination of VOCs emitted from painted building materials

Yoshikazu Sugesaka¹, Tsutomu Matuura¹, Susumu Aoyama¹ and Ken Yamamoto¹

(Received 4 December 2002, Accepted 20 January 2003)

A simplified analytical method using a milliliter-sized vial, which could be used to estimate the concentration of volatile organic compounds (VOCs) at room atmosphere emitted from each source, such as a building material, adhesive or paint, was established. When the concentration of VOCs in real living space was supposed, the result of this small-sized measurement could be a good reference. The sensitivity of GC/MS on an air sample measurement was sufficient for a direct analysis. For a small-sized sample measurement, although there was a problem of VOCs emission from each face, except for the surface, which should be evaluated, its influence could be reduced by masking any unnecessary faces using sealing materials, such as an aluminum tape.

Keywords : VOC; small-sized measurement; concentration in real living space.

Fractional determination of sodium chondroitin sulfate/hydroxypropylmethylcellulose mixture using Alucian Blue 8GX

Manabu Hattori¹, Junya Arita¹, Nobuhito Tabuchi¹, Shigeyuki Koike² and Hiroshi Nakamura³

(Received 27 December 2002, Accepted 17 February 2003)

Using Alucian Blue 8GX (AB), a simple fractional determination method was developed for sodium chondroitin sulfate (ChS-Na) and hydroxypropylmethylcellulose (HPMC) respectively in a drug. From a sample solution containing both ChS-Na and HPMC, ChS-Na was precipitated selectively as the ChS-Na-AB complex under a low-pH condition. After dissolution of the ChS-Na-AB complex in an alkali solution, ChS-Na was determined by the absorbance at 615 nm. The supernatant of the sample solution was subjected to gel permeation chromatography (GPC). The amount of HPMC was determined by the peak height of HPMC. These methods have safty, high-specificity and high-repeatability. These methods are therefore useful for drugs which contain both acidic mucopolysaccharide and a non-ionic polymer.

Keywords : sodium chondroitin sulfate; hydroxypropylmethylcellulose; Alucian Blue; absorbance; gel permeation chromatography.

Notes

Development and evaluation of reaction gas chromatograph as a calibration method using an index compound

Takuro Watanabe¹, Kenji Kato¹, Nobuhiro Matsumoto¹ and Tsuneaki Maeda¹

(Received 6 November 2002, Accepted 23 January 2003)

In order to realize a technique that serves as a calibration method using an index compound, reaction gas chromatography was examined. An index compound represents a group which includes many compounds; compounds in this group can be calibrated using the index compound. The gas chromatograph/micro reactor/mass spectrometer (GC/MR/MS) consists of a capillary gas chromatograph/mass spectrometer and a micro reactor. By using the MR, alkenes and alkynes were transformed to alkanes having the same carbon skeleton. Ethylene in a cylinder was determined using ethane as an index compound. The results showed good agreement with a reference value. The hydrodechlorination of chlorobenzenes was examined. Chlorobenzene in a solution was determined by using benzene as an index compound. The experimental results and reference concentration showed a good agreement. The efficacy of this technique was demonstrated with these results.

Keywords : micro reactor; reaction gas chromatography; GC/MS; hydrogenation; hydrodechlorination; calibration method; index compound.

Determination method of serum albumin using a Bromocresol Green solution and a Bromocresol Purple solution containing no detergent as a color reagent

Yuji Suzuki¹

(Received 3 July 2002, Accepted 14 February 2003)

Various detergents have been used in the dye-binding method for the determination of human serum albumin to prevent precipitation of the serum protein. However, there is problem that some detergents contained in the color reagent cause water pollution. Thus, the author studied the dye-binding method for determining human serum albumin using a Bromocresol Green (BCG) solution and a Bromocresol Purple (BCP) solution containing no detergent as a color reagent. The precipitation of serum protein occurred in the pH range of 3.8 to 4.2 for BCG, and 4.2 to 4.6 for BCP. Thus, pH 3.4 and pH 5.2 were selected for the pH of the BCG and BCP color reagents, respectively. In measuring a number of patients' sera, the precipitaion of serum protein was not observed at all in both BCG and BCP color reagents containing no detergent. The measurement values obtained by the proposed BCG method correlated very well with those by the conventional BCG method (r=0.997, y=0.983x-0.807, n=90) and the conventional BCP method (r=0.984, y=0.849x+5.57, n=90). The measurement values obtained by the proposed BCP method correlated well with those by the conventional BCP method (r=0.961, y=0.809x+7.55, n=90) and the conventional BCG method (r=0.948, y=0.913x+2.39, n=90). The mean values of the proposed BCG and BCP methods and the conventional BCG and BCP methods were 36.6, 37.2, 38.1 and 36.6 g/l, respectively.

Keywords : dye-binding method; serum albumin determination; Bromocresol Green; Bromocresol Purple; prevention of water pollution.

Determination of halogens by low-pressure helium ICP-MS

Hideo Hayashi¹, Yasuhisa Hara¹, Tomokazu Tanaka¹ and Masataka Hiraide¹

(Received 18 November 2002, Accepted 18 February 2003)

A low-pressure ICP formed with helium has been utilized as an ion source for MS, which is capable of providing information about traces of iron, arsenic and selenium without any interference from ArO⁺, ArCl⁺ and Ar²⁺, respectively. The present paper describes the application of a novel ICP for the determination of fluorine, chlorine, bromine and iodine, because the ionization of these halogens is highly suppressed in the case of conventional argon ICP (e.g., 9×10^-4% for fluorine). A 5 ml aliquot of an aqueous sample was placed on a looped tungsten filament and heated electrothermally at ca. 2500°C . The resulting sample vapor was transported to the ICP with a stream of helium. The analytes (¹⁹F⁺, ³⁵Cl⁺, ⁷⁹Br⁺ and ¹²⁷I⁺) were then determined by a quadrupole mass analyzer. The detection limits (ng ml^-1, based on 3σ) were 23 (F), 2.4 (Cl), 0.13 (Br) and 0.05 (I), which were much better than those of argon ICP. The absolute detection limits using 5 ml of a sample reached to the sub-picogram range. Especially, the detectability for fluorine was significantly improved, which allowed a direct determination of fluorine at the ng ml^-1 level in water.

Keywords : low-pressure helium ICP-MS; electrothermal vaporization; halogen; fluorine.

Technical Letters

A method for evaluation of photocatalytic decomposition of dimethyl sulfide by gas chromatography

Harumitsu Nishikawa¹, Zen-ichi Yamada², Masaaki Maekawa²,

(Received 25 December 2002, Accepted 7 February 2003)

Keywords : GC; photocatalytic decomposition; dimethyl sulfide.

Digests of Doctoral Dissertation

Development of chemical analysis methods for fine ceramics and related materials

Mitsuyoshi Watanabe

Chemical Analysis, Materials Research Laboratory, NGK Insulators, Ltd., 2-56 Suda-cho, Mizuho-ku, Nagoya-shi, Aichi 467-8530

(Awarded by Chiba University dated March 14, 2001)

This work was undertaken to elucidate the relationship between various characteristics of ceramic materials and their chemical composition, and to establish standard methods of chemical analysis for the standard ceramic materials to be used for fluorescent X-ray analysis. Therefore, various sample decomposition methods and measurement methods were developed for the chemical analysis of ceramics and related materials. In the first study, non-oxide ceramics samples were analyzed for the content of silicon nitride, silicon carbide, and boron carbide. In the analysis of silicon nitride, a determination method for small amounts of fluorine and surface oxygen was also established. With these tests, the relationship between the conditions of the sample synthesis and the chemical composition had been clearly shown. In the second study, the analysis samples were made of the oxide ceramics zirconium oxide, zinc oxide and lanthanum manganites. A determination method was established for silicon in zirconium oxide, and then silicon and aluminum in zinc oxide. The precision of the valence determination method of manganese in lanthanum manganites was also improved. The third study describes the chemical analysis methods for impurity elements in carbon and sulfur. This study establishes chemical analysis methods for the main component and impurity elements in fine ceramics and related materials.

(Received January 16, 2003)

Keywords : fine ceramics; non oxide ceramics; oxide ceramics; impurity elements; main component element.

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