Vol. 53 No. 4
April, 2004
Zenko Yoshida1, Sorin Kihara2 and Taitiro Fujinaga3
1 Department of Materials Science, Japan Atomic Energy Research Institute, Shirakata 2-4, Tokai, Ibaraki 319-1195(Received 15 December 2003, Accepted 6 February 2004)
A quantitative electrolysis of an electro-active species in a sample solution can be achieved very rapidly when the solution is allowed to flow through and be electrolyzed at a column electrode. Complete electrolysis of the species is attained with a small over-voltage, even if the electrode reaction is slow, because the species is electrolyzed repeatedly during a long residence-time of the solution in the column. The electrolytic method using the column electrode is suitable for automated or remote-controlled operation. Because of such unmatched advantages as mentioned above, the column-electrode electrolysis method has been widely applied to the coulometric determination of species in a flowing sample solution and to liquid chromatography as a coulometric detector. This technique is especially favorable for elucidating mechanism of such complicated reactions as that involving unstable intermediates. In the present article, a principle and a feature of the column-electrode electrolysis, an electrolytic chromatography and a coulopotentiography are presented and the advantages of these methods are reviewed based on recent works on the application to flow-injection analysis and to a study of the reox reaction of actinide ions or biomolecules as well as the reaction of short-lived radicals.
Keywords : column electrode; flow-electrolysis; coulometry; chromatography; analytical application.
Kei Toda1
1 Department of Environmental Science, Faculty of Science, Kumamoto University, 2-39-1, Kurokami, Kumamoto-shi, Kumamoto 860-8555(Received 28 November 2003, Accepted 15 January 2004)
Micro or miniature devices have been developed for flow analysis to obtain excellent performance. Some kinds of devices that we have developed are discussed in this paper. One of the advantages of miniaturization is a small reagent consumption and a field affordable size for “environmentally-friendly environmental analysis”. The miniature device is better for not only the operational usefulness, but also for the performance of the instrument. For example, a perfect collection efficiency is obtained in an electrochemical detection system microfabricated in a thin-layered wall-jet cell, and incubation is not needed in an enzyme-immobilized capillary cell. A small heat capacity is necessary for thermal detection, and a high-performance thermal sensor for flow enthalpimetry has been developed using a small stainless steel capillary. A gas diffusion scrubber has also been miniaturized so as to be placed into a flow system. The small diffusion scrubber has a large surface-to-volume ratio so that the sample gas is highly accumulated into the absorbing solution. The solution volume of the diffusion scrubber is same as that of the sample loop of FIA-sample-injector, and the scrubber is suited for being combined with the conventional flow injection system. Near real-time measurements of atmospheric gases have been conducted with miniature gas diffusion scrubbers and flow injection systems. In addition, novel collection/detection cells were developed for measuring atmospheric gases in-situ in a cell using the stopped-flow method.
Keywords : miniature device; flow injection analysis; electrochemical and thermal detection; atmospheric gas measurement.
Hiroyuki Ukeda1
1 Faculty of Agriculture, Kochi University, Monobe B-200, Nankoku-shi, Kochi 783-8502(Received 21 November 2003, Accepted 13 January 2004)
Reactive oxygen species (ROSs) and various free radicals are known to cause serious diseases, such as cancer and arteriosclerosis, and to accelerate aging. In order to protect our health from oxidative stress, active research has been carried out on screening antioxidants that can quench or scavenge ROSs and free radicals formed in our body. In the present paper, several novel flow-injection analysis (FIA) systems are discribed for estimating the antioxidative activity rapidly and conveniently, as follows: (1) spectrophotometric and chemiluminometric FIA for estimating the superoxide dismutase (SOD) and superoxide anion-scavenging activity (SOSA), (2) amperometric FIA for monitoring the catalase activity, which can decompose hydrogen peroxide, (3) FIA for 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity using electron spin resonance (ESR) as a detector, and (4) spectrophtometric FIA for 2,2'-azino-bis(3-benzthiazoline-6-sulfonic acid)(ABTS) radical-scavenging acitivity. Applications to practical samples, such as biochemical materials and foods, are also described.
Keywords : flow-injection analysis; food analysis; reactive oxygen species; free radical; immobilized enzyme; chemiluminescence; electron-spin resonance; superoxide dismutase; catalase; review.
Noriko Ohno1 and Tadao Sakai2
1 Chemistry Laboratory, School of Business Administration, Asahi University, 1851, Hozumi, Mizuho-shi, Gifu 501-0296(Received 27 November 2003, Accepted 20 January 2004)
Sensitive and selective flow injection systems coupled with liquid-liquid extraction were proposed. Extraction/FI systems were applied to the determination of quaternary ammonium salts (R4N+) in pharmaceuticals, anionic surfactant and dissolved oxygen in environmental water samples. A homemade thermo-controlled flow cell was used for the selective determination of cationic surfactants. Also, several kinds of phase separators were designed. Especially, a double-membrane phase separator gave efficient and constant separation with long-term continuous runs. Consequently, the proposed solvent-extraction/FIA systems are useful for the analyses of pharmaceuticals and environmental pollutants.
Keywords : flow-injection analysis coupled with solvent-extraction; double-membrane phase separator; thermo-controlled flow cell; pharmaceuticals; environmental pollutants.
Michio Zenki1
1 Department of Chemistry, Faculty of Science, Okayama University of Science, 1-1, Ridai-cho, Okayama-shi, Okayama 700-0005(Received 1 December 2003, Accepted 19 January 2004)
Circulatory flow-injection methods (cyclic FIA) are reviewed for the reuse of reagents that are present in excess. The application of cyclic FIA allows the repetitive determination and monitoring of analytical species. A new concept that detection can be carried out in the presence of an “inhibitor” makes it possible to recycle of the reagent solution successfully. Moreover, regenerations of the main reagent by means of ion exchange and chelate resins are presented. Examples of repetitive determination and monitoring for strong acids and bases (copper, calcium, chloride and ascorbic acid) are given. The advantages of cyclic FIA including minimization of the reagent and waste, long-run operation, and excellent reproducibility and robustness are also presented.
Keywords : cyclic flow-injection analysis; monitoring; repetitive determination; reuse of reagents; zero emission.
Shigenori Nakano1, Norio Teshima2, Makoto Kurihara3 and Takuji Kawashima4
1 Department of Environmental Sciences, Faculty of Education and Regional Sciences, Tottori University, 4-101, Minami, Koyama-cho, Tottori-shi, Tottori 680-8551(Received 27 November 2003, Accepted 15 January 2004)
Highly sensitive and selective flow-injection (FI) methods are presented for the determination of trace elements at nanogram and/or subnanogram per milliliter levels. These FI methods are based on the catalytic action of the elements on coloration and chemiluminescent (CL) reactions: (1) the oxidative coupling reactions of 3-methyl-2-benzothiazolinon hydrazone with modified Trinder's reagents, p-anisidine with N,N-dimethylaniline (DMA) and 4-aminoantipyrine with DMA in the presence of hydrogen peroxide; (2) the oxidation of 3,3',5,5'-tetramethylbenzidine, N-(3-sulfopropyl)-3,3',5,5'-tetramethyl-benzidine, N,N'-bis(hydroxyl-3-sulfopropyl)-tolidine and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid by hydrogen peroxide, bromate or periodate; and (3) CL reactions of luminol, lucigenin, pyrogallol and purpurogallin. In order to increase the sensitivity and/or selectivity of the FI methods, suitable ligands that acted as activators and surfactants were used in the catalyzed reaction systems. Elements such as copper(II), chromium(III), cobalt(II), iron(II,III), manganese(II) and vanadium(IV,V) in the range of 10-11~10-8 M could be determined by the FI methods with easy handling, rapid sampling frequency and good precision. Furthermore, a new approach for the catalytic FI method, FI/standard subtraction, was demonstrated by using the activation and inhibitory effect of a ligand in the metal-catalyzed reaction. The use of CL reactions allowed the determination of the oxidation state of iron and vanadium. These methods have been successfully applied to the determination of trace elements in both standard materials and actual samples.
Keywords : catalyzed reaction; redox reaction; chemiluminescence; flow injection analysis; activator; surfactant; metal ions.
Kouji Takahashi1, Akira Kotani1, Sanae Ohtsuki1 and Fumiyo Kusu1
1 School of Pharmacy, Tokyo University of Pharmacy and Life Science, 1432-1, Horinouchi, Hachioji-shi, Tokyo 192-0392(Received 17 November 2003, Accepted 22 December 2003)
A novel method for determining the titratable acidity of a pH adjuster using a flow-injection analysis system with electrochemical detection (FIA-ECD) has been developed. The detection is based on the voltammetric reduction prepeak of vitamin K3 in the presence of acids. The prepeak current is proportional to the equivalent concentration of the acids. A pH adjuster (DP-7L) for boiled noodle to prevent proliferation of bacteria, which contains lactic, phosphoric, and gluconic acid was used as an example in this study. Using FIA-ECD, the peak current height was proportional to the concentration of DP-7L between from 0.0012% to 0.01% (r=0.997). The relative standard deviation (RSD) of DP-7L at 0.0075% was determined to be 3.8% (n=5). The result obtained from the proposed method agreed well to with that from the titration volume of a NaOH standard solution by neutralization titration (r=0.989). Thus, the titratable acidity of the DP-7L pH adjuster can be determined by the present method. An auto analyzer being incorporated with the FIA-ECD would be useful for monitoring the titratable acidity of pH adjusters in the manufacturing process of boiled noodles.
Keywords : Flow-injection analysis; electrochemical detection; vitamin K3; pH adjuster.
Yumi Kato1, Yui Ishii1, Shinji Fujioka2, Mikita Ishii1,2 and Masaaki Yamada3
1 TLO, Japan Analysis & Evaluation Center (JAEC), 1-41-8, Kitanodai, Hachioji-shi, Tokyo 192-0913(Received 28 November 2003, Accepted 15 January 2004)
As one of the analytical applications to welfare supporting technologies, the most simplified single line flow injection (FI) system was successfully designed for sulfur determination by solution chemiluminescence detection. The reaction flow cell in the detection system was equipped with commercial Nalgen capillary tubing of 1 mm i.d. and 2 mm o.d. spiraled to ca. 5 cm size. The photomultiplier tube {R 376, made by Hamamatsu Photonics Co.Ltd. (Shizuoka Pref.)} was used for chemiluminescence detection. The chemiluminescent reaction using an emitter (Rhodamine B) and a non-ionic surfactant (Tween 80) was based on the dissolved oxygen oxidation of sodium hydrogen sulfite. Rhodamine B and Tween 80, which contributed to chemiluminescence enhancement, also played key roles in energy transfer and a surfactant micellar effect,respectively. The lower detection limit and the determination range of the proposed method were 2.0×10-6 M and 2.0×10-6 M to 1.5×10-5 M using 20 µl sample injections of sodium hydrogen sulfite, respectively. The analytical time required was less than 10 s for one sample. The reproducibility in 10 repeated runs by 20 µl sample injections of 1.4×10-5 M sodium hydrogen sulfite was 2% in terms of the relative standard deviation. The selectivity of the proposed method was good, and 1×10-5 M of foreign compounds gave no interference to coexistence in 1×10-4 M sodium hydrogen sulfite. Both of the amount and chemical species of the exhausted material in the present method were smaller in compared to those in the iodometric sulfite anion determination method (JIS method).
Keywords : analytical welfare supporting technology; sulfur; FIA; zero emission; dissolved oxygen oxidation chemiluminescence detection.
Masato Uechi1, Terufumi Fujiwara1 and Yasuaki Okamoto1
1 Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1, Kagamiyama, Higashihiroshima-shi, Hiroshima, 739-8526(Received 1 December 2003, Accepted 27 January 2004)
For the selective determination of agrichemicals containing copper, “Oxine-copper”, in aqueous samples, a flow method based on the combination of on-line liquid-liquid extraction with a reversed micellar mediated chemiluminescence (CL) detection was established. The analyte, which contained bis(8-quinolinolato)copper(II) as a major component, was extracted into chloroform from an aqueous sample bufferd at pH 6.0, followed by membrane phase separation in the flow system. In a flow cell of a detector, the extract was mixed with a reversed micellar solution of cetyltrimethylammonium chloride in chloroform-cyclohexane (6:5 v/v)-water containing luminol. At the reversed micellar interface, the extracted copper(II) complex dissociated rapidly to produce copper(II) ion. The released copper(II) ion catalyzed the CL oxidation reaction of luminol. Using a reverse-flow injection system, a detection limit of 5.5 µg dm-3 and a linear calibration graph with a dynamic range of up to 1.1 mg dm-3 were obtained for oxine-copper under the optimized experimental conditions. The effect of interference that would be caused by co-existing chemical species was also described.
Keywords : agrichemicals containing copper(II); chemiluminescence; flow-injection analysis; oxine-copper; reverse micelles.
Miho Tanaka1, Yasuyuki Watanabe1, Shinsuke Ohno1, Takaomi Tamaru1, Norio Teshima1 and Tadao Sakai1
1 Department of Applied Chemistry, Aichi Institute of Technology, 1247, Yachigusa, Yakusa-cho, Toyota-shi, Aichi 470-0392(Received 1 December 2003, Accepted 14 January 2004)
The reduction reaction of iron(III) with cobalt(II) easily occurs in the presence of 2-(5-nitro-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)phenol (nitro-PAPS) at pH 3.5, in which iron(II)-nitro-PAPS chelate is formed. The chelate has a specific absorption maximum at 790 nm. Cobalt(II) can thus be determined by measuring the absorbance of the complex at the above-mentioned wavelength. The redox reaction is introduced into a two-channel flow system for the determination of cobalt(II). The calibration curve is linear in the concentration range of 2.5×10-7 M~1×10-5 M cobalt(II) with a sample throughput of 70 samples h-1. The detection limit (S/N=3) is 1×10-7 M and the relative standard deviation for 10 determinations is 0.3% for 2.5×10-6 M cobalt(II). The proposed flow-injection spectrophotometric method is applied to analyses of cobalt(II) in cobalt alloy (NIST SMR 862; High Temperature Alloy L 605) and pepperbush (NIES standard, No. 1) and to the indirect determination of vitamin B12 in pharmaceuticals.
Keywords : cobalt(II); iron(III); nitro-PAPS; redox reaction; flow-injection.
Takeshi Yamane1, Takefumi Tsuchimoto1 and Hiroyasu Yoshikawa2
1 Faculty of Education and Human Sciences, Yamanashi University, 4-4-37, Takeda, Kofu-shi, Yamanashi 400-8510(Received 5 December 2003, Accepted 23 January 2004)
The in-line cation-exchange separation of lead and cadmium from coexisting elements utilizing a malate solution as an eluent, which also serves for the enrichment and mutual separation of both metals, is directly coupled with photometric detection in a continuous-flow system. The photometric detection system developed here exploits the formation of a water-soluble complex of lead and cadmium with TMPyP [(5,10,15,20-tetrakis(N-methyl-pyridynium-4yl)-21H,23H-porphine, tetrakis(p-toluenesulfonate)] in a basic medium (pH 10.1). Various analytical parameters were investigated, and the optimal conditions and manifold configurations were established. A linear calibration using a 2.5 m sample loop was obtained for both metals in the range of 0~0.1 ppm. The relative standard deviations for 0.03 ppm of each metal were 0.6% and 1.5%, respectively. The estimated limits of determination are ca. 0.001 ppm for lead and ca. 0.002 ppm for cadmium. The results for the analysis of three sysnthetic soil sample solutions(prepared from soil extracts) and of certified reference river warter (JAC 0032) corresponded well with those obtained by ICP-AES methods and certified value, respectively. The present FI system affords a rapid and simple analysis: only 10 min is required for analytical measurements after sample injection, and no complicated manual operation is involved.
Keywords : flow-injection system; cation-exchange separation; spectrophotometric detection with TMPyP; lead and cadmium; river water and soil sample.
Kazuya Takada1, Tetsuo Uchida1 and Yosuke Nakai1
1 Department of Applied Chemistry, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya-shi, Aichi 466-8555(Received 20 November 2003, Accepted 8 January 2004)
A powdered 25.0 mg sample was decomposed with 0.5 ml of hydrochloric and 0.2 ml of hydrofluoric acids at room temperature, and then diluted with water to 25.0 g after adding 2.4 ml of 4% boric acid. SiO2, Al2O3 and T-Fe2O3 were measured using molybdenum ammonium, stilbazo and 1,10-phenanthroline, respectively. A FIA system consisting 2-stream system was simple and common to the 3 components. Na2O and K2O were measured simultaneously with ion selective electrodes connected in parallel. Only FeO, another 25.0 mg sample, was treated with 0.6 ml perchloric and 0.2 ml hydrofluoric acids coexisting of vanadium(V) and then diluted as above. FeO was measured with 3-stream FIA system. The proposed acid decomposition was simple and easy for many samples. The analytical results of major constituents in standard rocks agreed well with the recommended values.
Keywords : major constituents in silicates; acid decomposition; spectrophotometry; ISE; FIA.
Tomonori Tsuboi1, Yoshio Hirano1, Kazuyoshi Kinoshita2, Mitsuko Oshima2 and Shoji Motomizu2
1 The Chugoku Electric Power Co. Inc., Technical Research Center, 3-9-1 Kagamiyama, Higashi-Hiroshima-shi, Hiroshima 739-0046(Received 3 December 2003, Accepted 4 February 2004)
A rapid and simple spectrophotometric determination method for chemical oxygen demand in water samples was developed using a flow-injection method. The detection method is based on the permanganate oxidation reaction accelerated by a catalyst. A platinum tube reactor was installed after the merging point of a carrier and a reagent stream as a catalyst and a reactor coil, and was heated at 95°C by an aluminum heating block. By using the platinum tube reactor (0.5 mm i.d.×3 m), a standard sample, D-glucose, was measured within a few minutes, and the calibration graph was linear from 0 to 100 ppm of COD(D-glucose); the detection limit corresponding to S/N=3 was 0.01 ppm. The relative standard deviations for 5, 10, 50 and 100 ppm of COD(D-glucose) were 0.9, 0.8, 0.8, 0.5 and 1.4%, respectively. The proposed FIA system can be applied to waste water or can be used as a monitor of COD.
Keywords : chemical oxygen demand; FIA; spectrophotometry; platinum catalyst; potassium permanganate; waste water.
Kiyoko Takamura1, Norihiro Nakamichi1 and Chiyo Matsubara1
1 Tokyo University of Pharmacy and Life Science, 1432-1, Horinouchi, Hachioji-shi, Tokyo 192-0392(Received 28 November 2003, Accepted 30 January 2004)
A Ti-TPyP reagent, i.e., an acidic aqueous solution of oxo{5,10,15,20-tetra(4-pyridyl)porphyrinato}titanium(IV)complex, was developed as a highly sensitive spectrophotometric reagent for determining traces of hydrogen peroxide. Following the addition of hydrogen peroxide to the reagent, a new absorption peak appeared at 450 nm due to the formation of its monoperoxo complex. The absorbance at 450 nm was found to be proportional to the hydrogen peroxide concentration with an apparent molar absorptivity of 1.1×105 M-1 cm-1. Based on this fact, we conducted a highly sensitive analysis of hydrogen peroxide using the reagent coupled with the flow-injection analysis (FIA) method with a detection limit of 0.5 pmol per test (S/N=3). In this study, the method was assessed for determining glucose, urate and galactose levels in human serum using the corresponding oxidase enzyme columns incorporated with the FIA system. The determinations of glucose and urate were successfully made with small sample sizes, i.e., 0.05 and 0.5 ml serum, respectively. The response was linear against concentrations ranging 1~1000 and 0.5~600 µM (5~5000 and 2.5~3000 pmol/test) for glucose and urate, respectively. The throughput rate was 40 samples per hour. Both cases required no sample pretreatment procedure, such as deproteinization or preconcentration, and the obtained results were consistent with those obtained by the conventional methods. The galactose level in serum was much lower than that of glucose and urate; however, the determination of galactose could be made by the present method using 20 µl of bdeproteinized serum. The response was linear against the galactose concentration in the range of 0.5~500 µM (10~10000 pmol/test). Galactose levels ranging over 0.54~1.46 mg/dl could actually be obtained for normal serum samples. The recovery values for 0.90 mg/dl (50 µM) galactose added to the samples were 96~104.9%.
Keywords : flow-injection analysis; Ti-TPyP reagent; glucose; urate; galactose.
Youhei Yamada1, Masayo Ogai1, Keiro Higuchi2, Norio Teshima1 and Tadao Sakai1
1 Department of Applied Chemistry, Aichi Institute of Technology, 1247, Yachigusa, Yakusa-cho, Toyota-shi, Aichi 470-0392(Received 1 December 2003, Accepted 2 February 2004)
Diquat(DQ2+) and paraquat(PQ2+) are dipyridinium herbicides, which are toxic to humans. These compounds react with an ion-association reagent, TBPEH, dissolved in 1,2-dichloroethane (DCE), to form blue ion associates: (DQ2+·(TBPE-)2) and (PQ2+·(TBPE-)2). A two-line flow system was assembled. Buffer (pH 11.0) and TBPEH/DCE solutions were delivered at 0.8 ml min-1. The associate was extracted in a 5 m extracting coil. However, when a DCE waste phase containing the ion associate and aqueous waste, including TBPE ion, were mixed with 5 ml of 3 mol dm-3 sulfuric acid and stirred, yellow TBPEH was formed in DCE again. On the other hand, DQ2+(PQ2+) ion was transferred to the acidic aqueous phase. Therefore, TBPEH was regenerated in DCE and the TBPEH/DCE solution could be reused as an ion-association reagent/extracting solvent. A recycled FIA system using regenerated TBPEH with DCE was proposed. The calibration graphs were linear over the range from 0.25×10-5 mol dm-3 to 2.0×10-5 mol dm-3. When a reused reagent/DCE was delivered, the same calibration graph was obtained for DQ2+. In the case of PQ2+, the slope of the calibration graph decreased slightly; however, the linearity was good. The method was applied to the determination of DQ2+ or PQ2+ in herbicides and artificial samples. The proposed FIA is a novel and excellent method with no consumption of reagent or organic solvent.
Keywords : diquat and paraquat; recycled FIA with extraction; tetrabromophenolphthalein ethyl ester; reuse of ion-association reagent/organic solvent.
Kei Okamura1, Hiroshi Hatanaka2 and Yoshiki Sohrin1
1 Institute for Chemical Research, Kyoto University, Gokasho, Uji-shi, Kyoto 611-0011(Received 1 December 2003, Accepted 8 January 2004)
A manganese analyzer powered by micro-diaphragm pumps has been developed to monitor time-series changes of manganese concentrations in seawater in situ. The analyzer determines the concentration of dissolved manganese in a continuous manner using a H2O2-luminol CL method. The analyzer uses micro-diaphragm pumps to propel solutions. This pump possesses the following advantages for long-term observations: (1) reducing the pump size and power requirements and (2) small flow rate. In the present case, the power requirements and reagents flow rate could be reduced by using a thin Teflon tube (0.5 mm I.D.), and had a 98% response time of approximately 6 min, the same as before.
Keywords : diaphragm pump; manganese; seawater; time series monitoring; in situ.
Tomomi Watanabe1, Ken Sasaki1, Keiko Jyonosono1, Nobuaki Soh1, Toshihiko Imato1, Noriyuki Imazumi2, Masayuki Nakanishi2 and Jun-ichi Yagi2
1 Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, 6-10-1, Hakozaki, Higashi-ku, Fukuoka-shi, Fukuoka 812-8581(Received 27 November 2003, Accepted 19 January 2004)
A flow-injection titration method proposed by us was applied to the determination of the total base number (TBN) in a lubricant during an oxidation test. The method is based on measurements of the absorbance change of an indicator contained in an acid-base buffer solution or the potential change of a pH glass electrode detector, which is generated due to a neutralization reaction of base compounds in the lubricant with the acid-base buffer solution. To measure the absorbance change, a three-channel manifold with a spectrophotometric detector was constructed, i.e., a carrier stream of a mixed solvent (toluene 52%/H2O 1%/2-propanol 47% v/v), a stream of perchloric acid and a stream of tetrabutylammonium salt of trifluoroacetic acid solution containing an indicator (m-cresol purple). The absorbance change of an acidic form of m-cresol purple was proportional to the total concentration of the base compounds in the lubricants. When the method was applied to the determination of TBN in lubricants during oxidation test, a good linear correlation was observed for the analytical results between our proposed method and a conventional neutralization titration method. However, some lubricant samples with a deep-brown color after the oxidation test deviated from a linear correlation. This was due to the fact that light absorption of the colored lubricant interferes with the absorbance measurement of the color change of the indicator. For a measurement of the potential change, the same manifold as that for a measurement of the absorbance change was used, except for the pH glass electrode detector and a stream of tetrabutylammonium salt of trifluoroacetic acid solution without m-cresol purple. TBN in the lubricants during the oxidation test, which were determined by our proposed method based on measurements of the potential change, was in good agreement with that determined by the conventional titration method, even for the lubricant samples with a deep-brown color.
Keywords : total base number; oxidation test; lubricant; potentiometric FIA; pH buffer solution.
Zhen Hai Li1, Mitsuko Oshima1 and Shoji Motomizu1
1 Department of Chemistry, Faculty of Science, Okayama University, 3-1-1, Tsushimanaka,Okayama-shi, Okayama 700-8530(Received 2 December 2003, Accepted 4 February 2004)
Boron as boric acid was determined as a complex with chromotropic acid at pH 6.0 in an aqueous medium by fluorescence detection/flow-injection analysis. The complex was detected by measuring the fluorescence intensities (λex=313 nm, λem=360 nm). EDTA was used as a buffer component with the role of a masking agent to metal ions. The background fluorescence of chromotropic acid could be decreased by mixing with 0.1 M ammonia water after complex formation, resulting in a stable baseline. The calibration graph was rectilinear over 10-9~10-6 mol dm-3 (M), and the detection limit was 5×10-10 M (S/N=3). The reproducibility was 3.61% (n=10, with the peak height) at 6×10-9 M of boron and sample throughput was 40 h-1. Applications to river water, ion-exchanged water and distilled water could be achived without any pretreatments. For the analysis of ultrapurified water, an evaporation/preconcentration procedure was carried out, because the concentration was under the LOD and no reference water which could be used for the carrier solution or preparation of the reagent solutions.
Keywords : boron; chromotropic acid; ultrapurified water; fluorescence/flow injection analysis.
Tatsuya Seki1 and Koichi Oguma2
1 Chemical Research Laboratories, Nissan Chemical Industries, Ltd., 722, Tsuboi-cho, Funabashi-shi, Chiba 274-8507(Received 1 December 2003, Accepted 27 January 2004)
A flow injection method has been developed for the determination of uranium in natural waters and high-purity aluminum by use of on-line preconcentration on a U/TEVATM column and ICP-MS detection. The sample solution prepared as a nitric acid solution in 3 mol l-1 was passed through the U/TEVATM column to collect uranium and uranium adsorbed was eluted with 0.1 mol l-1 nitric acid. The effluent was introduced directly into the nebulizer of the ICP-MS and 238U was measured. The detection limit, calculated as 3-times the standard deviation of the background noise, was 3 pg and the sample throughput was about 10 per hour. The proposed method was successfully applied to the determination of uranium in river-water reference materials, a seawater reference material and high-purity aluminum reference materials.
Keywords : flow injection; uranium; on-line preconcentration; natural water; high-purity aluminum.
Hideji Tanaka1
1 Faculty of Pharmaceutical Sciences, The University of Tokushima, Shomachi 1-78-1, Tokushima-shi, Tokushima 770-8505(Received 31 October 2003, Accepted 9 December 2003)
A new system of flow ratiometry having UV detection without a phase separator was developed and applied to the determination of the chloroform/water distribution coefficients (KD) of phenol and its derivatives. An aqueous solution of analyte and chloroform was delivered independently and merged at various flow ratios (Rf). The ratio was changed stepwise. Both phases, segmented each other, passed through an extraction coil and were directly led to a flow cell, where the absorbance of each phase was monitored. A wide-bore tubing (2 mm, i.d., 20 cm long) was inserted between the extraction coil and the flow cell in order to coalesce the chloroform segments and/or aqueous segments. Thus formed bigger segments were easily measured. The KD was calculated from the slopes and the intersections of linear plots of A-1 vs. Rf, (ARf)-1 vs. Rf-1, and ARf vs. A, where A is Ao (absorbance of chloroform phase), Aa (absorbance of aqueous phase), DA (=Ao-Aa) or SA (=Ao+Aa). Among them, the plots using SA as A gave the best results, probably due to a cancellation of the intrinsic errors in the Ao and Aa measurements. The method was simple and efficient (<5 min/determination) with satisfactory precision.
Keywords : stepwise flow ratiometry; distribution coefficient; partition coefficient; flow extraction; detection without phase separation.
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