Vol. 4 8, No. 2
February, 1999
Hiromiti Sawamoto**
**Faculty of Education, Kochi University, 2-5-1 Akebono-cho, Kochi 780-8520
(Received 7 July 1998)The adsorptive stripping voltammetry of various metal ions is described while emphasizing the ligands used, sensitivities and practical applications. First, the historical development of polarography is mentioned. Stripping voltammetric methods involving preconcentration by charge transfer reactions are described. Cathodic and anodic adsorptive stripping voltammetric methods are described for riboflavin as an example. In the preconcentration of adsorptive stripping voltammetry of metal ions, the adsorption of complexes is employed. The adsorptive stripping voltammetry of nickel with 2,2'-bipyridine (ligand)is explained. Metals are classified according to the periodic table (Table 1) and the adsorptive stripping voltammetric methods are described. The ligands which are frequently used to form complexes are listed in Table 2. Ultrasensitive catalytic adsorptive stripping voltammetry, which exhibits sensitivity down to pM, is also described.
Keywords: stripping voltammetry; metal ions; mercury electrode; adsorption; complex.
Shoji Motomizu**
**Department of Chemistry, Faculty of Science, Okayama University, Tsushimanaka, Okayama 700-8530
(Received 6 October 1998)Studies on ion association and its reaction mechanism were reviewed from the viewpoint of analytical chemistry. Ion association has been extensively used for the separation and analysis of ionic substances by coupling with other methods, such as solvent extraction, precipitation, adsorption on hydrophobic adsorbents, titration, reversed-phase/HPLC, flow injection analysis and capillary electrophoresis. First, a historical background concerning ion association in analytical chemistry, electrolyte solutions and water structures around ions is reviewed; secondly, theoretical aspects of ion association are summarized; thirdly, analysis methods for ion-association equilibrium in aqueous solutions are reviewed; last, ion-association mechanisms in aqueous solutions and in liquid-liquid distribution are considered. From the present reviews, classifying ions into three groups is proposed: they are water-structure former (WSF), water-structure breaker (WSB) and hydrophobic water-structure promoter (HSP). The ion associability of each ion with its pairing ion is considered. In analytical chemistry, important ion associates are electrostatic interaction-induced ion associates and hydrophobic water structure-induced ion associates.
Keywords: ion association in analytical chemistry; analysis methods for ion association; mechanism of ion association; ion-association models; electrostatic interaction-induced ion association; hydrophobic water structure-induced ion association; ion associability in aqueous solutions.
Hiroyuki Ukeda**
**Faculty of Agriculture, Kochi University, Monobe B-200, Nankoku-shi, Kochi 783-8502)
(Received 21 September 1998, Accepted 10 November 1998)A convenient and rapid analytical system for food components responsible for food quality was developed based on the use of immobilized enzymes and microorganisms. First, an analytical system for superoxide dismutase (SOD) activity was constructed using the combination of an immobilized enzyme with flow-injection analysis (FIA). In this system, the immobilized xanthine oxidase played the role of a generator of superoxide anion; the sampling frequency was about 30 samples/h. Next, a novel analytical format was proposed involving a combination of immobilized enzymes with a 96-well microtiter plate. An alternate and repeated deposition of avidin and biotinylated enzyme was useful for enzyme immobilization with high activity and stability. Immobilized glucose oxidase under the optimized conditions was applicable to glucose determination, and the acitivity was retained during storage for 6 months and 50 successive determinations. The ability of microorganisms to recognize a given group of substances is useful for exploiting novel analytes. An example was indicated by the development of a rapid and convenient analytical system for short-chain fatty acids using immobilized Arthrobacter nicotiana-FIA. A sample throughput of 20 samples/h was achieved, and the obtained response showed a linear correlation with the total concentration of C4:0 to C12:0. The response was also partly related to the somatic cell count in raw-milk samples (n=150), suggesting that the system should be applicable to detecting mastitis milk. The application of immobilized Psuedomonas putida to the determination of organic acids in wine is also described, in which the relationship between the specificity and the carbon sources used in the growth medium was investigated.
Keywords: immobilized enzyme; immobilized microorganism; flow injection analysis; microtiter plate assay; food analysis; review.
Yuriko Kiba and Yoshinobu Baba**
**Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, The University of Tokushima, Shomachi, Tokushima 770-8505
(Received 1 October 1998, Accepted 11 November 1998)Recently, much attention has been focused on the association of the higher order structure of genomic DNA, human gene, and mRNA with genetic and common diseases. For example, a change in the higher order structure of genomic DNA or mRNA induced by an expansion of trinucleotide repeats may cause some inherited neuromuscular diseases, called triplet-repeat diseases. We investigated the capillary electrophoretic behavior for triplet-repeat DNA fragments in detail and found that even a large triplet-repeat DNA fragment moves much faster than a small random-sequence DNA fragment within a capillary filled with a polymer solution. We proposed modified reptation theory to help understand such an unusual electrophoretic behavior, succeeded to estimate the drastic change in the persistence length of the triplet repeat DNA fragment, and elucidated the higher order structure of the human gene associated with genetic and common diseases. It showed that triplet-repeat DNA fragments are less flexible than single-stranded standard DNA fragments because of the higher order structures formed by the characteristic GC-rich sequences of triplet-repeat DNA fragments. In this study we established new method to investigate and elucidate the higher order structures of genomic DNA, human gene, and mRNA by capillary electrophoresis with high speed, high accuracy, and high sensitivity.
Keywords: triplet repeat disease; capillary electrophoresis; reptation theory; conformational analysis.
Hiroshi Yamashita**
**Department of Applied Chemistry, Faculty of Engineering, Ehime University, 3, Bunkyo-cho, Matsuyama-shi, Ehime 790-8577
(Received 1 October 1998, Accepted 12 November 1998)Spherical porous ceramics particles were synthesized by the sol-gel process from tetramethoxysilane(TMOS), methyltrimethoxysilane, zirconyl chloride, zirconium tetrapropoxide and titanium tetraisopropoxide in a W/O emulsion, respectively. The pore size of silica gels could be controlled to within 4 to 600 nm by changing the compositions of polyethyleneglycol (PEG), H2O and the organic solvent in the starting solutions. The interconnected pore structure of the gels could be made by eliminating PEG from the gel bodies. Spherical silica glass particles with an interconnected pore structure were synthesized from spherical borosilicate particles by successive thermal and acid treatments. The size of the pores could be controlled to within 10 to 50 nm by selecting the temperature and time of the thermal treatment. Zirconia particles were obtained by the addition of urea and hexamethylenetetramine in the starting solution. The peak pore- diameter of the particles was 4 nm. The pore volume increased with an increase in the calcium content. After the extraction of calcium by hot water, the specific surface area of the particles was enhanced by 110 m2/g. SiO2-ZrO2 binary particles were synthesized by using zirconium tetrapropoxide and 2-methoxyethanol. The specific surface area of the particles was 260 m2/g. After extraction of the SiO2 parts by a 1 M NaOH aqueous solution, the weight loss of the particle was 10 mass%. Titania particles were obtained by the addition of diethanolamine or 2-methoxyethanol in the starting solution. The peak pore-diameter of the particles was 4 nm. TiO2-SiO2 binary particles were synthesized by using 2-methoxyethanol. The specific surface area of the particles was 180 m2/g after extraction of the SiO2 parts by a 0.1 M NaOH aqueous solution.
Keywords : silica; zirconia; titania; porous particles; sol-gel method; W/O emulsion.
Minoru Okumura, Kaoru Fujinaga and Yasushi Seike**
**Interdisciplinary Faculty of Science and Engineering, Shimane University, 1060, Nishikawatsu-cho, Matsue-shi, Shimane 640-8504
(Received 6 October 1998, Accepted 16 November 1998)An effective and selective adsorbent, activated carbon loaded with zirconium (Zr-C*), has been developed for the preconcentration of phosphate in environmental water samples. The Zr-C* was prepared by mixing a zirconyl nitrate solution with activated carbon. Phosphate is quantitatively adsorbed onto Zr-C* below pH 8 and quantitatively desorbed above pH 13.5. Such quantitative adsorption and desorption were instantaneously accomplished. These characteristics of Zr-C* enable us to separate and preconcentrate rapidly and selectively low levels of phosphate in environmental water samples by two rapid preconcetration methods. One is a flow method: a sample solution (pH 1.5) is passed through a Zr-C* bed formed on a membrane filter paper with the aid of suction to preconcentrate phosphate; the collected phosphate is then recovered by eluting with a 1 M sodium hydroxide solution. This method is effective for high concentrations of phosphate at low levels. The other method is column solid-phase extraction: a small column packed with Zr-C* is used for the in situ preconcentration of phosphate in field work. Both methods were successfully applied to environmental waters samples.
Keywords: preconcentration of phosphate; activated carbon loaded with zirconium; adsorption and desorption; column solid phase extraction; environmental water.
Yasunobu Kato, Tetsu Kumagai, Shigeroku Yamaguchi and Hiroshi Nishioka*
*Faculty of Engineering and School of Humanity for Environment Policy and Technology, Himeji Institute of Technology, 2167, Shosha, Himeji-shi, Hyogo 671-2201
(Received 11 August 1998, Accepted 22 September 1998)A rapid measurement of chemical oxygen demand (COD) was studied based on the ultra-violet absorption spectra and partial least squares method. The COD calibration models for mixture of some organic compounds were made from the ultra-violet-absorption spectra and visible-absorption spectrum, the COD values of samples were then predicted with good precision.
Keywords: chemometrics; ultra-violet visible photometry.
Kunihiro Watanabe, Fumio Nakadai, Manami Sakiyama, Kazue Yamaguchi and Masayuki Itagaki*
**Faculty of Science and Technology, Science University of Tokyo, 2641, Yamazaki, Noda-shi, Chiba 278-8510
(Received 12 August 1998, Accepted 15 October 1998)The effect of tiron as an activator on the color-fading of Hydroxy Naphthol Blue (HNB) has been investigated by spectrophotometry. HNB was decomposed by the hydroxy radical formed with hydrogen peroxide in the presence of Co(II). The formation of the hydroxy radical was enhanced remarkably by the addition of tiron in the presence of a trace amount of Co(II). The behavior of a HNB decomposition reaction was applied to the catalytic determination of Co(II). The interesting effect of tiron was examined on the radical reaction in the presence of Co(II). Tiron acts as an activator when in high concentrations on the hydroxy radical-forming reaction. On the other hand, a low concentration of tiron works as an inhibitor in that reaction. In this study, it has been established that tiron suppressed Co-HNB(1:2) complex formation, which was an inert complex on the radical formation. The active complex in hydroxy-radical formation was Co-HNB(1:1), containing tiron and hydrogen peroxide. The procedure of Co(II) determination was follows. A sample solution of 35 ml containing less than 2 µg of Co(II) had its pH adjusted to 12.8 with a NaOH solution; then, after 5 ml of 0.5 M CAPS as a buffer solution, 5 ml of 6.0×10-2 M tiron solution and 1 ml of a 1.2×10-3 M HNB solution were added the solution, was diluted with water to 49 ml. After standing for 5 min at 25°C, 1 ml of a 24% hydrogen peroxide solution was added. Then, the pH of sample solution was varried to 10.8 after the addition of hydrogen peroxide. The values (A1, A5) of the absorbance were read at 650 nm after 1 min and 5 min. A calibration curve was obtained by the relationship between ln(A1/A5) and the concentration of Co(II). The detection limit of Co(II) was 0.03 ppb. Cobalt (II) was determined over 0.09~40 ppb by the present method. Furthermore, a stepwise determination method of Co(II) and Mn(II) with HNB was investigated. As a result, Co(II) in the range of 0.3~30 ppb was determined by the present method after the determination of Mn(II).
Keywords: Hydroxy Naphthol Blue; tiron; catalytic determination; cobalt(II); stepwise determination.
Masamitsu Nakagawa, Jin-Ming Lin, Tatsuro Nakagama, Katsumi Uchiyama and Toshiyuki Hobo*
*Department of Applied Chemistry, Graduate School of Engineering, Tokyo Metropolitan University, Minami-Ohsawa 1-1, Hachioji-shi, Tokyo, 192-0397
(Received 7 July 1998, Accepted 29 October 1998)In this study, some uncharged hydrophobic compounds, such as p-arylacetophenones, polycyclic aromatic hydrocarbons and steroids, were separated by micellar electrokinetic chromatography (MEKC) using amide solvents containing sodium n-dodecyl sulfate (SDS), di-(2-ethylhexyl) sodium sulfosuccinate (AOT) or taurodexycholic acid sodium salt (STDC). The separation was shown to be dependent on the types of amide solvent and the surfactant concentration. Three different amides, formamide (FA), N-methylformamide (NMF) and N,N-dimethylformamide (DMF) were used as solvent. A satisfactory result was obtained in formamide/SDS/NaH2PO4 medium. The effects of the amide solvent, surfactant and electrolyte on the separation were also studied.
Keywords: micellar electrokinetic chromatography; surfactant; nonaqueous; hydrophobic compounds.
Kunikazu Ide, Muneyuki Kohri, Koichi Sato*, Yoshinori Inoue** and Haruno Okochi***
*National Research Institute for Metals, 1-2-1, Sengen, Tsukuba-shi, Ibaraki 305-0047
**Yokogawa Analytical Systems Inc., 2-11-19, Nakacho, Musashino-shi, Tokyo 180-0006
***Science University of Tokyo, 1-3, Kagurazaka, Shinjuku-ku, Tokyo 162-8601
The solid-phase extraction (SPE) of organotin compounds, such as monobutyltin (MBT), monophenyltin (MPT), dibutyltin (DBT) and diphenyltin (DPT) in seawater has been developed. An ion exchange-type solid-phase sorbent (Excelpak SPE-ION/C224, Yokogawa Analytical Systems Inc., Japan) having a hydrophillic and strong acidic sulfopropyl group and a cation-exchange resin (CK08P, Mitsubishi Chemicals, Japan) were comparatively investigated. The recovery of organotin compounds was measured by atomic-absorption spectrometry, and hydride purge & trap/ICP-MS in the case of ultra-trace organotin compounds. The variables affecting SPE were investigated by using a 2.5% sodium chloride solution instead of seawater, such as the amounts of sorbent, the conditioning of cation exchange resins, the flow rate and pH of sample solutions, the effect of the amounts of sodium ion, removing of adsorbed sodium, and an eluting agent. After all, the cation exchange resin was chosen to be a SPE sorbent, because it has a higher ion-exchange capacity and exhibits better recoveries of organotin compounds. Ten to twelve ml of a strong acidic cation exchange resin (pH 1.0) of sample solutions and a flow rate of 5~6 ml min-1 gave good results. For removing adsorbed sodium ions from the resins, 100 ml of 0.5 M hydrochloric acid was rinsed after injecting every 125 ml of a sample solution of 2.5% sodium chloride solution containing organotin compounds. The eluent was 14 ml of 0.5 M hydrochloric acid-methanol solution. DBT and DPT were completely recovered from the solution up to 500 ml of artificial seawater, also MBT and MPT were also recovered up to 250 ml. Ultra traces of MBT, MPT, DBT and DPT were determined perfectly by using the present SPE system followed by the hydride purge & trap/ICP-MS.
Keywords: solid phase extraction; organotin compounds; ICP-MS; hydride generation; purge & trap; seawater.
Keiro Higuchi*, Akiko Inoue**, Tomonori Tsuboi*** and Shoji Motomizu*
*Department of Chemistry, Faculty of Science, Okayama University, 3-1-1 Tsushimanaka, Okayama 700-8530
**FIA Division, Tokyo Kasei Kogyo Co. Ltd., 6-15-9, Toshima, Kita-ku, Tokyo 114-0003
***The Chugoku Electric Power Co., Inc. Technical Research Center, 3-9-1, Kagamiyama, Higashi-Hiroshima, Hiroshima 739-0046
A new on-line gas-permeation system was developed to enhance the efficiency and stability of gas permeation for a long time, and was applied to the determination of ammonium ion in river-water samples by the flow- injection method. The proposed gas-permeation system consists of a newly designed gas-permeation unit, a sample injection valve, a reaction coil and two six-way rotary valves in a constant-temperature oven. The gas- permeation unit was assembled using an inner microporous polytetrafluoroethylene (PTFE) membrane tubing and an outer glass tube, which could be easily connected with one another using connectors with ferrules and o-rings. A sample solution was injected into a carrier containing 0.02 M sodium hydroxide, in which ammonium ion was converted to gaseous ammonia. The gaseous ammonia generated in the carrier passed through the microporous PTFE membrane, was absorbed in a reagent solution and changed the pH of the reagent solution, which resulted in a color change to cresol red. The absorbance change of cresol red at 550 nm was measured using a visible detector with a flow cell (8 µl, 10 mm path). After the measurement, two six-way rotary valves were switched over from the flowing state to the drain state of the gas-permeation unit, and the residual solutions in the gas-permeation unit were removed and the PTFE membrane tubing was dried. By keeping the temperature of the oven at 40°C, the sensitivity and the reproducibility for the determination of ammonium ion was improved. Furthermore, the efficiency of gas permeation through the inner tubing could be kept high and constant for a long period without any procedure for reactivating the porous PTFE membrane tubing. Calibration graphs for ammonium ion were liner over ranges of 0 to 10 ppm and 0 to 1.0 ppm of N-NH4+, and the sampling rate was 30 samples per hour. The detection limit for N-NH4+ was about 0.01 ppm when the effective length of the membrane tubing was 5 cm. By using the proposed FIA system, ammonium ion in river-water samples was determined. The analytical results obtained by the proposed method showed a good correlation with those obtained using the indophenol derivatization/FIA method. The relative standard deviations of ten injections were 0.51% and 0.83% with concentrations of 2.73 ppm and 4.11 ppm, respectively. The recoveries of ammonium ion were found to be 97~98%.
Keywords: gas permeation system; microporous polytetrafluoroethylene membrane tubing; FIA with gas permeation method; determination of ammonium ion; river water sample.
Kimitoshi Sato, Mitsuhisa Monden and Takashi Goto*
*Department of Industrial Chemistry, College of Engineering, Nihon University, 1, Nakagawara, Tokusada, Tamura, Koriyama-shi, Fukushima 963-8642
(Received 29 July 1998, Accepted 16 October 1998)The separation and preconcentration of trace Cd from water samples for a graphite-furnace AAS determination was studied using silica gel loaded with 4-(2-Pyridylazo)-resorcinol (PAR)/Capriquat. A sample solution of 100~700 ml containing Cd was adjusted to pH 11. The solution was then passed through a column packed with 300 mg of PAR/Capriquat-loaded silica gel at a flow rate of 10 ml min-1. The Cd collected on the PAR/Capriquat-loaded silica gel column was eluted with 5 ml of 0.5 M nitric acid, and then determined by GF-AAS. In this method, over 99% of the Cd was preconcentrated at about pH 11. The calibration curve was linear over the range 0.02 to 2.5 µg/l of cadmium. The proposed method has been applied to the determination of Cd in seawater samples.
Keywords: cadmium; PAR/Capriquat loaded silica gel; graphite furnace AAS; seawater.
Masaaki Ishikawa*1, Rieko Matsuda, Yuzuru Hayashi*2, Chikako Yomota*3, Akira Yamaguchi, Kazuo Iwaki*4, Hirotaka Obana*5, Moritoshi Sato, Tetsuya Yoshida*6 and Masahiko Tsuji*7
*1Fuji Health Center, 441-1 Hon-Ichiba, Fuji-shi, Shizuoka 416-0906
*2National Institute of Health Sciences, 1-18-1 Kami-Yoga, Setagaya-ku, Tokyo 158-8501
*3Osaka Branch, National Institute of Health Sciences, 1-1-43 Hoenzaka, Chuo-ku, Osaka 540-0006
*4Center for Technology Development, Ebara Research Co. Ltd., 4-2-1 Honfujisawa, Fujisawa-shi, Kanagawa 251-8502
*5Osaka Prefectural Institute of Public Health, 3-69, Nakamichi 1-chome, Higashinari-ku, Osaka 537-0025
*6Nagano Research Institute for Health and Pollution, 1978 Amori Kome-mura, Nagano 380-0944
*7Hyogo Prefectural Institute of Public Health, 2-1-29 Arata, Hyogo-ku, Kobe 652-0032
The limit of detection (LOD) was determined for three p-hydroxybenzoic acid esters at nine laboratories. The result of each laboratory was analyzed by computer software (called TOCO) which predicts the precision and LOD based on the baseline fluctuation without repeated measurements. In every laboratory, the shorter was the retention time of the analytes, the lower was the LOD. In each analyte, the peak-height measurement was more precise than the entire area measurement. The LOD obtained by the laboratories ranged from 0.16 to 30 µg/l. The validity of the TOCO, when applied in practical situations, has been proved.
Keywords: limit of detection (LOD); precision; HPLC.
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