Vol. 54 No. 12
December, 2005
Toshihiko Imato1
1 Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, 744, Motooka, Nishi-ku, Fukuoka-shi, Fukuoka 819-0395(Received 31 July 2005, Accepted 18 October 2005)
Flow analysis has many advantages concerning sensitivity, accuracy, repeatability and analytical throughput etc, compared with a batchwise analysis. The flow-based method makes the involved analytical processes automatic and rapid. Therefore, the combination of a chemical sensor with the flow method enhances the performances of the chemical sensor. Especially, potentiometric detection using ion-selective electrodes has been widely used in flow analysis due to its features, simplicity in analytical operation and wide dynamic range in analysis. This paper reports on several chemical sensors applied to flow systems that we have engaged so far concerning: (1) Liquid membrane type ion-selective electrodes, such as nitrate, vitamin B1, tetrafluoroborate and surfactants sensitive electrodes based on an oleophilic anion exchange resin membrane and a hydrophobic ion exchanger. (2) Flow titration by using both a buffer solution and its corresponding electrode, such as a pH glass electrode with a pH buffer, a cupper(II) ion-selective electrode with a metal ion buffer solution and a redox electrode with a potential buffer solution. (3) Surface plasmon resonance sensors for succarides and some endocrine disrupting chemicals based on a boronic acid polymer membrane and antigen or antibody immobilized membrane. (4) Sequential injection analysis combined with beads injection technique for vitellogenin as biomarker for assessing the pollution of environment in hydrosphere.
Keywords : flow analysis; ion-selective electrode; sequential injection analysis; surface plasmon resonance sensor; beads injection.
Shiro Matsuoka1 and Kazuhisa Yoshimura2
1 Department of Environmental Science, Faculty of Science, Niigata University, Ikarashi, Niigata-shi, Niigata 950-2181(Received 4 August 2005, Accepted 18 September 2005)
Solid-phase spectrometry (SPS) is based on the direct spectrometric measurement of solid phase which has sorbed a sample component. Direct application of the method mekes it possible to determine trace components in water samples without preconcentration. This method could be applied to a new type of FIA detection system, in which on-line detection with solid-phase retention of analytes is carried out. The sensitivity enhancement is easily accomplished by increasing the sample volume introduced. Analytes present in the µg~sub-µg dm-3 range can be easily determined by using this system. The fundamental background and applicability of SPS and FI-SPS are described.
Keywords : solid phase; spectrometry; flow analysis; high sensitivity; speciation.
Yoichi Shibusawa1, Naoko Takeuchi1, Heisaburo Shindo1 and Yoichiro Ito2
1 Division of Structural Biology and Analytical Science, Tokyo University of Pharmacy and Life Science, 1432-1, Horinouchi, Hachioji-shi, Tokyo 192-0392(Received 27 June 2005, Accepted 31 August 2005)
Phospholipids were fractionated by high-speed counter-current chromatography in a one-step operation from about 0.75 g of hen egg yolk using a type J-multilayer coil planet centrifuge. The partition coefficients values of phospholipids were measured in several two or three-solvent systems. The separation of phospholipids was performed with a two-phase solvent system composed of chloroform/n-heptane/n-butanol/methanol/60% acetic acid (2 : 3 : 2 : 3 : 5) by eluting the lower phase at a flow-rate of 1.0 ml/min. The phospholipids in each fraction were characterized by thin-layer chromatography.
Keywords : countercurrent chromatography; two or three-phase systems; hen egg yolk phospholipids; partition coefficient.
Yoriko Sasaki1, Aki Daikokuya1, Isoshi Nukatsuka1 and Kunio Ohzeki1
1 Department of Materials Science and Technology, Faculty of Science and Technology, Hirosaki University, 3, Bunkyocho, Hirosaki-shi, Aomori 036-8561(Received 19 July 2005, Accepted 7 October 2005)
A flow injection spectrophotometric method for the determination of ammonia and formaldehyde was developed, in which ammonia and formaldehyde were determined with almost the same FIA manifold. The color development reaction of ammonia is based on the formation of an indonaphthol dye in the presence of hypochlorite and 1-naphthol. The FIA system consisted of three flow paths: a carrier (water), a NaClO solution, and a 1-naphthol solution in a mixed solvent (ethanol : acetone : water=2 : 1 : 2), with flow rates of 0.2, 0.2, and 0.4 ml min-1, respectively. A monochloramine and an indonaphthol dye were formed in a reaction coil (RC1) and a reaction coil (RC2), respectively. The optimum conditions were thoroughly studied by varying the reagent concentrations under a fixed flow rate. The results showed that the optimum conditions were 0.25 M NaOH and 2.0% active chlorine for a NaClO solution, and 1.6% of 1-naphthol. The lengths of the required reaction coils were 3 m and 7 m for RC1 and RC2, respectively. A linear calibration graph was obtained in the range of 0~2 µg ml-1, and the detection limit, based on three-times the standard deviation of a blank, was 15 ng ml-1. Formaldehyde was determined indirectly using the reaction with ammonia to form hexamethylenetetramine. The residual ammonia was determined with the same FIA system, except that RC1 was replaced by a 20 m reaction coil. The concentration of active chlorine was set to 1.2%. A linear calibration graph was obtained in the range of 0~1 µg ml-1, and the detection limit was 13 ng ml-1. The time required for the analysis of one sample was 8.1 min for ammonia and 14.8 min for formaldehyde. The time interval required for successional injection of the sample was about 5.5 min in both methods. The proposed method was applied to obtain a decay curve of formaldehyde in a test chamber in the absence or presence of an absorbent for formaldehyde. It was found that an ammonium sulfate solution is effective to absorb formaldehyde in air.
Keywords : ammonia; formaldehyde; 1-naphthol; ammonium sulfate; flow injection analysis.
Makoto Harada1, Tomo-o Kido1 and Tetsuo Okada1
1 Department of Chemistry, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8551(Received 22 July 2005, Accepted 30 September 2005)
Theoretical simulations have been conducted to explain the elution profiles of solutes passed through an open capillary and to analyze the potential usefulness of this simple technique as a separation method. The advection-diffusion equation for a cylindrical geometry has been numerically analyzed with a CIP method, which is known to be a suitable method for numerical simulations of differential equations. The profile of the solute distribution in a capillary can be characterized by four factors: the diffusion coefficient of the solute, the flow rate and the radius and length of the capillary. The reduction time (tav) is a very good measure to represent the diffusivity of a solute; it is diffusive when tav>1, but nondiffusive when tav<1, as stated in our previous papers. A diffusive solute is carried by the average flow, and gives a Gaussian-shaped peak, while a nondiffusive solute moves along the Poiseuille flow profile in the capillary and produces an asymmetrical peak appearing earlier than the former. The mechanisms for the production of these different peak profiles have been discussed in detail based on the results of a simulation. Although two solutes can be separated based on this separation principle, the heavy peak-tailing of the asymmetric peak makes complete separation difficult. To reduce the tailing, several possibilities for sample introduction and effluent collections have been proposed. Numerical simulations have suggested that such improvements result in a much better separation performance.
Keywords : laminar flow; CIP; hydrodynamic chromatography; diffusion.
Yuko Tomotsune1, Tomohiko Kawakami1,2, Satoshi Tomatsuri1, Tsuneyuki Noguchi1,
1 Kaken. Co., 1044, Hori, Mito-shi, Ibaraki 310-0903(Received 22 July 2005, Accepted 17 October 2005)
Concerning analysis in a microfluid, so-called µTAS, the precision of the analysis is greatly affected by the flow-rate precision of the pump used. In response to this required precision of the pump, we have developed a gas-pressurized micro fluidic pump (µFPump) without any pulsation. Its applicability was examined by comparing the precision to that of a currently used pump, such as a micro-syringe pump and a diaphragm pump. The precision was compared through a model analysis, a quantitative analysis of nitrite ion in JIS K 0102 (Industry drainage examination under Japanese Industrial Standards), using a glass-made microchemical-chip as a reaction chip and a Thermal Lens Microscope as a detector. As a result of the comparison experiment, in the case of an analysis using our µFPump, a coefficient of variation (CV) of 0.7~2.0% and a detection limit (3σ) of 0.0058 mg/ml were obtained, and it was clarified that a several-fold higher analytical precision than that of using the other pumps can be obtained. Moreover, the experiment indicates that a pump with stable flow without pulsation is necessary to carry out an accurate analysis in a microfluid.
Keywords : micro fluidic pump; pulsation; µTAS; flow stability; gas pressurized pump.
Kiyoko Kurosawa1, Katsuyoshi Tatenuma1, Manabu Muto2, Hiroyasu Esumi2 and Yukio Kanda3
1 KAKEN Co. Ltd, 1044, Horimachi, Mito-shi, Ibaraki 310-0903(Received 22 July 2005, Accepted 6 October 2005)
In order to measure a small amount of constituent in gaseous samples, such as measuring the causative substances of the sick-house syndrome, according to general solid-phase adsorption, complicated handling, such as solvent extraction, or concentration and heating desorption, are required. Consequently, we have developed a simple and highly accurate continuous gas sampler consisting of a denuder and a cross flow nebulizer. An absorbing solution and gaseous sample are simultaneously introduced to the nebulizer, and a droplet absorbent is then flowed in the inner wall of the denuder tube, while contacting with the gaseous sample. By optimizing the flow ratio between the gaseous sample and the absorbent, the targeted constituent in the gaseous sample is efficiently absorbed into the absorbent while flowing in the tube. By experiments being currently conducted, in the case of formaldehyde recovery under the condition of a gaseous sample flow rate of 2.0 l/min and an absorbent (purified water) flow rate of 0.1 ml/min (volume ratio of gaseous sample/absorbent=20000 : 1), a recovery rate of 95% or more was stably and continuously obtained, and a concentration of less than 1/10 of the regulated formaldehyde concentration in a room can be analyzed without any extraction or concentration procedures. We will apply this simple gas sampler to practicable technologies, such as the recovery of other volatile organic compounds (VOC) constituents, an on-site sick-house monitoring system with a detective device, and cancer diagnosis using expiratory air.
Keywords : denuder; nebulizer; gas-sampler; sick-house monitor; formaldehyde.
Tadao Sakai1, Shun-ichi Fujimoto1, Keiro Higuchi2 and Norio Teshima1
1 Department of Applied Chemistry, Aichi Institute of Technology, 1247, Yachigusa, Yakusa-cho, Toyota-shi, Aichi 470-0392(Received 22 July 2005, Accepted 22 September 2005)
An automatic flow injection method was proposed using the on-line solid-phase extraction of trace phenols and color development with 4-aminoantipyrine. Phenols at low levels in water samples were pre-concentrated onto OASIS HLB for 20 min at 2 ml min-1. After elution, color development occurred in the merging zone with 4-aminoantipyrine buffered at pH 10 and hexacyanoferrate(III). The absorbance was measured at 505 nm. The calibration graph for phenol was linear over the range of 0.25~10 ng ml-1 with RSD<1%. The proposed method could be applicable to the analysis of phenols in tap and river water.
Keywords : solid-phase extraction; trace phenol analysis; automatic flow injection method; 4-aminoantipyrine method.
Masato Suzuki1, Tomoyuki Yasukawa1, Hitoshi Shiku1 and Tomokazu Matsue1
1 Graduate School of Environmental Studies, Tohoku University, 604, 6-6-11, Aramaki-Aoba, Aoba-Ku, Sendai-shi, Miyagi 980-8579(Received 25 July 2005, Accepted 19 October 2005)
The dielectrophoretic separation of micro-organisms, based on cellular membrane damage, was carried out using a microfabricated fluidic device. The fluidic device was composed of an indium-tin oxide electrode with castellated electrode patterns, an acrylic board with inlet and outlet holes for micro-organisms suspension, and a silicone separator with a fluidic channel (width, 2 µm; length, 35 mm) between the electrode substrate and acrylic board. Dielectrophoretic separation was demonstrated for a mixture of live and heat-treated Escherichia coli bacteria labeled by fluorescent stains. The mixture was injected into the fluidic device at a flow rate of 440 mm/sec. Both live and dead bacteria were collected around castellated electrode when an alternative (sinusoidal) electric field (frequency 100 kHz, voltage 20 Vpeak-to-peak) was applied to the castellated electrode. The dielectrophoretic separation was found by changing the electric field frequency from 100 kHz to 7 MHz. Only the heat-treated E. coli cells were flown out from the fluidic device, while the live E. coli cells remained being captured between the electrodes. The results demonstrated that the fluidic device equipped with a microelectrode array provides a convenient way for the dielectrophoretic concentration and separation of targeted bio-particles in biomedical applications.
Keywords : dielectrophoresis; biological particles; cell; micro-organism; dielectrophoretic separation.
Yasushi Hasebe1,2, Takayuki Shirai2, Tomohiro Nagashima1, Tingting Gu2 and Shunichi Uchiyama1,2
1 Department of Applied Chemistry, Faculty of Engineering, Saitama Institute of Technology, 1690, Fusaiji, Okabe-machi, Saitama 369-0293(Received 8 August 2005, Accepted 17 October 2005)
Thionine (TN) was adsorbed onto a porous carbon felt (CF) electrode surface, and the resulting TN-modified CF (TN-CF) was successfully used as a working electrode unit in a flow-through electrocatalytic detector, which enabled both the amperometric and coulometric determination of NADH at the µM concentration level. The anodic peak current due to the electrocatalytic oxidation of NADH was optimized for the highly sensitive amperometric and coulometric determination of NADH. The optimum conditions for the amperometric determination of NADH were the applied potential; +0.2 V (vs. Ag/AgCl); the carrier pH, 8.0 (0.1 M phosphate buffer); and the carrier flow rate, 2.5 ml min-1. The calibration curve of NADH, plotting the peak current vs. NADH concentration, is linear from 1 µM to 100 µM, with a detection limit of 0.5 µM. The reproducibility of the measurements was 1.35~1.70% RSD (n=10). The determination speed was up to 72 samples per hour at a flow rate of 3.5 ml min-1. In order to enhance the coulometric efficiency, a slower flow rate and a smaller sample volume were preferable. When the carrier flow rate was less than 0.8 ml min-1 and the sample volume was 20 µl, the charge efficiency for 100 µM NADH reached almost 100%, which enabled an absolute assay of NADH without any calibrations.
Keywords : carbon felt; NADH; thionine; FIA; amperometric and coulometric detector.
Masaaki Yoshiwara1, Akio Sakuragawa1 and Amane Mitsuhashi1
1 Department of Materials and Applied Chemistry, College of Science and Technology, Nihon University, 1-8-14, Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8308(Received 22 July 2005, Accepted 6 October 2005)
A flow injection system was developed for the determination of creatinine as an index of the progression of chronic renal failure, with an immobilized enzyme-reactor column. This system consisted of a hand-made reactor column packed with creatinine deiminase immobilized onto chitosan beads (CD-IE) as a carrier and utilized the glutaraldehyde bridging method by forming a Schiff base. Using a phosphate buffer solution as a carrier, the sample solution is injected into the stream. The injected sample solution is converted to ammonia by CD-IE reactor column, and the solution is made into a basic medium with potassium hydroxide. It is then introduced into a gas-diffusion device, and mixed with cresol red and 2-{4-(2-hydroxyethyl)-1-piperzinyl}-ethanesulfonic acid. The absorbance is measured at wavelength of 555 nm. In this study, it was converted from creatinine to ammonia by CD-IE reactor column, and creatinine was determined indirectly by the concentration of ammonia. Creatinine in the control urine for the proofreading of the automatic urine analysis was determined by applying the standard addition method. It was almost agreed with the reference value.
Keywords : creatinine; FIA; immobilized enzyme; creatinine deiminase; gas diffusion membrane process.
Kenichiro Todoroki1, Masae Arisaka1, Yoshihiko Nakashima1, Hideyuki Yoshida1, Hitoshi Nohta1 and Masatoshi Yamaguchi1
1 Faculty of Pharmaceutical Sciences, Fukuoka University, 8-19-1, Nanakuma, Johnan-ku, Fukuoka-shi, Fukuoka 814-0180(Received 23 June 2005, Accepted 4 October 2005)
We have developed a fluorescence derivatization method of 5-hydroxyindoles (serotonin, 5-hydroxyindole-3-acetic acid, N-acetylserotonin) based on benzylamine derivatization, followed by photocatalytic oxidation. In the present study, a photocatalyst, which was titanium dioxide supported on a diatomaceous earth particle, was used instead of potassium hexacyanoferrate(III) as a chemical oxidizing agent employed in the conventional method. The resulting fluorescent derivatives were separated by reversed-phase liquid chromatography on an ODS column by using a mixture of acetonitrile and 250 mM acetate buffer (pH 4.6) and detected spectrofluorimetrically at 465 nm with excitation at 350 nm. The detection limit (signal-to-noise ratio=3) for N-acetylserotonin was 16 fmol per 20 µl injection.
Keywords : liquid chromatography; 5-hydoroxyindoles; photocatalyst; fluorescence derivatization; benzylamine.
Kenji Yoshikawa1, Miho Okamura1, Miki Inokuchi1 and Akio Sakuragawa1
1 Department of Materials and Applied Chemistry, College of Science and Technology, Nihon University, 1-8-14, Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8308(Received 11 July 2005, Accepted 27 September 2005)
From the viewpoint of a graphite carbon column with excellent durability, it was applied to the ion chromatography (IC) of several organic acids. The carbon column was permanently coated with the cetyltrimethylammonium ion, and the elution behaviors of several organic acids (acetic acid, lactic acid, succinic acid, malic acid, tartaric acid, citric acid) and inorganic anions (Cl-, NO2-, NO3-, SO42-) were examined according to an ion chromatography that combined conductivity detector using a mobile phase of the benzoic acid system, when an ion-exchange ability was given to the graphite carbon column. Tartaric acid and citric acid, etc. with large valency showed tendency to which the width of each peak extended and the retention time increased. However it was possible to separate excellently for the analytes detected within ten minutes. The calibration curves obtained from the peak areas for the organic acids and inorganic anions were linear, with good correlation coefficients of 0.999. The relative standard deviations (RSD) of the peak areas were between 0.4 and 1.0 for six repeated measurements. The developed method was then applied to the determination of organic acids in several food samples.
Keywords : graphite carbon column; organic acids; benzoic acid-tris aminomethane; ion chromatography; vinegar samples.
Tomoko Nakano-Ohta1, Takashi Saito2 and Jun Sato1
1 Department of Industrial Chemistry, School of Science and Technology, Meiji University, 1-1-1, Higashi-mita, Tama-ku, Kawasaki-shi, Kanagawa 214-8571(Received 14 July 2005, Accepted 16 September 2005)
Radium isotopes (228Ra and 226Ra) in river-water samples from Japan having low concentrations were attempted to be collected by a Mn-impregnated acrylic fiber. The method was aimed at the in-situ collection of Ra isotopes in large amounts of river water by making effective use of the flow of the river to observe the 228Ra/226Ra activity ratio. Measurements of the 228Ra/226Ra activity ratios were made by non-destructive g-ray spectrometry. Although the collection efficiency of Ra isotopes by Mn-impregnated acrylic fiber was observed to be dependent on the water pH and temperature, the Ra isotopes in river water in an effective range of pH and temperature could be successfully collected. The 228Ra/226Ra activity ratios observed in several rivers of Japan by the present method were in the range of 1.1~2.9, which is slightly higher than those observed in rivers of the continental area.
Keywords : 228Ra/226Ra activity ratio; river water; Mn-impregnated acrylic fiber.
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