Hideji Tanaka

The University of Tokushima, Tokusima, Tokushima, Japan

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Publications (25)49.82 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Amplitude modulated multiplexed flow analysis (AMMFA) has been improved by introducing air segmentation and software-based phase recognition. Sample solutions, the flow rates of which are respectively varied at different frequencies, are merged. Air is introduced to the merged liquid stream in order to limit the dispersion of analytes within each liquid segment separated by air bubbles. The stream is led to a detector with no physical deaeration. Air signals are distinguished from liquid signals through the analysis of detector output signals, and are suppressed down to the level of liquid signals. Resulting signals are smoothed based on moving average computation. Thus processed signals are analyzed by fast Fourier transform. The analytes in the samples are respectively determined from the amplitudes of the corresponding wave components obtained. The developed system has been applied to the simultaneous determinations of phosphate ions in water samples by a Malachite Green method. The linearity of the analytical curve (0.0-31.0μmoldm(-3)) is good (r(2)>0.999) and the detection limit (3.3σ) at the modulation period of 30s is 0.52μmoldm(-3). Good recoveries around 100% have been obtained for phosphate ions spiked into real water samples.
    Talanta 01/2014; 118:123-8. · 3.50 Impact Factor
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    ABSTRACT: During the summer of 2011 and winter of 2012, we continuously measured trace acid gas concentrations in Tokushima, Japan, using a parallel plate wet denuder coupled ion chromatograph. The average concentrations of hydrochloric acid (HCl), nitrous acid (HONO), nitric acid (HNO(3)), and sulfur dioxide (SO(2)) were, respectively, 0.54, 1.20, 1.17, and 3.22 μg m(-3) in the summer, and 0.09, 1.06, 0.46, and 5.11 μg m(-3) in the winter. In the summer, concentrations of all the acid gases increased after sunrise and showed a strong diurnal pattern with daytime maxima and nighttime minima, but the time at which concentration levels began to increase and the pace of increase differed among the acid gases. The concentration of HONO increased sharply immediately after sunrise, while concentrations of the other three gases began increasing about one and half hours later. SO(2) showed the fastest rate of increase, followed by HNO(3) and HCl. These differences were likely attributable to the formation processes of gaseous substances.
    Analytical Sciences 01/2013; 29(1):165-8. · 1.57 Impact Factor
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    ABSTRACT: An automated analysis system has been developed for measuring perchlorate concentration in atmospheric aerosol. The perchlorate in aerosol sample, which has been collected with water mist in a hydrophobic filter/mist chamber based particle collector, is continuously preconcentrated. The matrix ions such as sulfate are subsequently removed from the preconcentrator. The remaining perchlorate is then analyzed on-line with an ion chromatograph in conjunction with a Nafion membrane tube based post-column concentrator. The sensitivity is increased by a factor of 7.7 with the post-column concentration technique. The proposed system has been successfully operated at Tokushima, Japan. The limit of detection is 0.35 ng/m(3) for 3 h sampling cycle. The perchlorate concentration in the atmospheric aerosol averaged 1.01±1.75 ng/m(3) (n=12).
    Talanta 08/2012; 97:527-32. · 3.50 Impact Factor
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    ABSTRACT: The concept of amplitude-modulated multiplexed flow analysis has been extended to the simultaneous determination of multiple analytes in a sample. A sample solution containing nitrite and nitrate ions is delivered from two channels, but the flow rates are varied at different frequencies. One of the channels has a reduction column for converting nitrate ions to nitrite ions. Downstream, the absorbance of the diazo-coupling product is monitored after the merging of both solutions with a Griess reagent. The signal is analyzed by a fast Fourier transform (FFT) in real time. From the thus-obtained amplitude, a µmol dm(-3) level of the ions can be determined. The introduction of air bubbles is effective to reduce any axial dispersion, and hence to improve the sensitivity.
    Analytical Sciences 01/2012; 28(5):523-5. · 1.57 Impact Factor
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    ABSTRACT: This paper describes the performance of our automated acidic (CH(3)COOH, HCOOH, HCl, HNO(2), SO(2), and HNO(3)) gases monitor utilizing a parallel-plate wet denuder (PPWD). The PPWD quantitatively collects gaseous contaminants at a high sample flow rate (∼8 dm(3) min(-1)) compared to the conventional methods used in a clean room. Rapid response to any variability in the sample concentration enables near-real-time monitoring. In the developed monitor, the analyte collected with the PPWD is pumped into one of two preconcentration columns for 15 min, and determined by means of ion chromatography. While one preconcentration column is used for chromatographic separation, the other is used for loading the sample solution. The system allows continuous monitoring of the common acidic gases in an advanced semiconductor manufacturing clean room.
    Analytical Sciences 01/2011; 27(8):805-10. · 1.57 Impact Factor
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    ABSTRACT: Air-segmentation is applied to amplitude-modulated multiplexed flow analysis, which we proposed recently. Sample solutions, the flow rates of which are varied periodically, are merged with reagent and/or diluent solution. The merged stream is segmented by air-bubbles and, downstream, its absorbance is measured after deaeration. The analytes in the samples are quantified from the amplitudes of the respective wave components in the absorbance. The proposed method is applied to the determinations of a food dye, phosphate ions and nitrite ions. The air-segmentation is effective for limiting amplitude damping through the axial dispersion, resulting in an improvement in sensitivity. This effect is more pronounced at shorter control periods and longer flow path lengths.
    Analytical Sciences 01/2011; 27(3):305-8. · 1.57 Impact Factor
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    ABSTRACT: Analytical conditions of amplitude-modulated multiplexed flow analysis, the basic concept of which was recently proposed by our group, are investigated for higher sample throughput rate. The performance of the improved system is evaluated by applying it to the determination of chloride ions. The flow rates of two sample solutions are independently varied in accordance with sinusoidal voltage signals, each having different frequency. The solutions are merged with a reagent solution and/or a diluent, while the total flow rate is held constant. Downstream, the analytical signal V(d) is monitored with a spectrophotometer. The V(d) shows a complicated profile resulting from amplitude modulated and multiplexed information on the two samples. The V(d) can, however, be deconvoluted to the contribution of each sample through fast Fourier transform (FFT). The amplitudes of the separated wave components are closely related to the concentrations of the analytes in the samples. By moving the window for FFT analysis with time, a temporal profile of the amplitudes can be obtained in real-time. Analytical conditions such as modulation period and system configuration have been optimized using aqueous solutions of Malachite Green (MG). Adequate amplitudes are obtained at the period of as low as 5 s. At this period, the calibration curve for the MG concentration of 0-30 micromol dm(-3) has enough linearity (r(2) = 0.999) and the limit of detection (3.3sigma) is 1.3 micromol dm(-3); the relative standard deviation of repeated measurements (C(MG) = 15 micromol dm(-3), n = 10) is 2.4%. The developed system has been applied to the determination of chloride ions by a mercury(II) thiocyanate method. The system can adequately follow the changes in analyte concentration. The recoveries of chloride ion spiked in real water samples (river and tap water) are satisfactory, around 100%.
    Analytical Sciences 01/2010; 26(7):791-6. · 1.57 Impact Factor
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    ABSTRACT: An amplitude-modulated flow analysis coupled with lock-in detection is proposed for the determination of trace phosphate. The flow rate F(S) of sample solution is varied in response to a periodic signal V(c) of alternating waveform. A coloring reagent solution (ammonium molybdate + Malachite Green) is delivered at a constant flow rate F(R). Under the constant total flow rate F(T), both solutions are merged with a diluent (water). Phosphate ion in the sample reacts with molybdate and then with Malachite Green to form green ion pairs in acidic media. Downstream, the absorbance of the mixed solution is measured at 625 nm. The output voltage V(d) from the detector is sent to a lock-in amplifier, where the wave component of V(d) that has the same frequency as that of V(c) is distinguished from background signals. Phosphate ion can be determined from the amplitude of the component thus extracted. The calibration curve is linear (r(2) > 0.998) and the limit of detection (3.3sigma) is 0.17 micromol dm(-3). Compared with a conventional flow-based method with no modulation, the present method is less susceptible to the baseline drift due mainly to the adsorption of the ion-pair on the optical window, because the quantification is based not on the absorbance itself but on the amplitude of the absorbance. Good recoveries around 100% are obtained for the phosphate ions spiked into real water samples.
    Analytical Sciences 01/2010; 26(7):797-801. · 1.57 Impact Factor
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    ABSTRACT: We propose a reversed phase HPLC (RP-HPLC) with an alkaline-resistant silica-based stationary phase, XBridge Shield RP(18), for the determination of the lipophilicity of drugs with diverse chemical nature ranging from acidic to basic. A set of 40 model compounds with well-defined solvatochromic parameters was selected to allow a broad distribution of structural properties. The chromatographic results showed that the lipophilicity index log k(w) obtained with XBridge Shield RP(18) was well correlated with experimental log P(oct) values (r(2)=0.96). Linear solvation free-energy relationship (LSER) analyses revealed that the retention mechanism of the stationary phase and 1-octanol/water partitioning were controlled by almost the same balance of intermolecular forces (hydrophobicity as expressed by the van der Waals volume V(w), H-bond acceptor basicity beta, and dipolarity/polarizability pi*). The results showed that XBridge Shield RP(18) phase overcomes the shortcomings of the silica-based stationary phases, the application of which to lipophilicity measurements had been limited to neutral and acidic compounds.
    CHEMICAL & PHARMACEUTICAL BULLETIN 11/2008; 56(10):1417-22. · 1.56 Impact Factor
  • Chemical & Pharmaceutical Bulletin - CHEM PHARM BULL TOKYO. 01/2008; 56(10):1417-1422.
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    ABSTRACT: We propose a new concept, amplitude modulated multiplexed flow analysis, for the simultaneous determination of multiple analytes from a single continuous analytical signal. The flow rates (FS1 and FS2) of two sample solutions are independently varied in response to trigonometric voltage signals each at a different anharmonic frequency. With the total flow rate FT held constant, the solutions are merged with a reagent solution that is aspirated to the confluence point at the flow rate of FT−FS1−FS2. Downstream, the analytical signal due to the mixed reacted solution, Vd, is monitored. Vd will show a complicated profile resulting from the trigonometrically varying flow rates of the sample solutions. The signal contains information on the multiple analytes. The signal can be demodulated to the contribution of each sample solution through fast Fourier transform (FFT). The amplitudes of the separated wave components are related to the concentration of the analytes in the sample solutions. By moving a window for FFT analysis with time, temporal profile of amplitudes can be obtained in real-time. We demonstrate the concept by applying it to the simultaneous determination of food dyes and to that of ferrous ions in two sample solutions.
    Talanta 01/2008; 77(2):576-580. · 3.50 Impact Factor
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    ABSTRACT: Lipophilicity was evaluated using a novel RP-HPLC stationary phase (Discovery-RP-Amide-C16) with and without 1-octanol added to the mobile phase. A set of 46 drugs and flavonoids characterized by a broad structural diversity and a wide log Poct range (-0.69 to 5.70) was selected for this study. This set consists of neutral solutes and solutes with acidic or ampholytic functionalities which were maintained neutral at pH 2.5 or 4. In our conditions, the addition of 1-octanol in the mobile phase proved a key factor to derive a lipophilicity index log k(w) highly correlated with log Poct for all investigated solutes. 1-Octanol improved the correlation between log Poct and log k(w) mainly by influencing the retention behavior of the solutes with log Poct values below +3. This study brings additional evidence that under proper experimental conditions of stationary and mobile phases, RP-HPLC is a very useful method to obtain log Poct values.
    Journal of Chromatography A 11/2005; 1091(1-2):51-9. · 4.61 Impact Factor
  • Hideji Tanaka, Tsutomu Baba
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    ABSTRACT: We propose a new approach for high-throughput continuous titration based on a flow ratiometry. The method was applied to potentiometric titrations of acids and bases. A base solution, the flow rate F(B) of which was varied in response to controller output voltage V(c), was merged with an acid solution under constant total (acid+base) flow rate. Downstream, the pH of the mixed solution was measured with a flow-through glass electrode. Initially, V(c), and thus F(B) was increased linearly. At the instant the equivalence point (EP) was sensed, the ramp direction of V(c) was reversed from upward to downward. The direction was reversed to upward when EP was sensed again. Such the feedback-based operation gives a triangular waveform of V(c), because there is a delay corresponding mainly to the transit time of merged solutions to reach the sensor. The value of V(c) that gives EP composition, V(E), was estimated by averaging the most recent maximum and minimum values of V(c). Next, fixed triangular waves of V(c) was used to control F(B). The amplitude and the scan rate of the waves were fixed narrower and faster, respectively, than those in the feedback-based operation in order to improve the throughput rate. The EP can be located as long as the scan range covers V(E). These automated processes limited the titration to just the narrow range around EP, and thus realized extremely high throughput rate of maximally 17.6 titrations per minute (=3.4s per titration) at R.S.D.=0.35%.
    Talanta 11/2005; 67(4):848-53. · 3.50 Impact Factor
  • Hideji Tanaka, Tsutomu Baba
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    ABSTRACT: The principle of flow ratiometry for high-throughput titration, which we recently proposed for potentiometric titration, was extended to photometric titration. The flow rate (FB) of a base solution containing an acid-base indicator was linearly varied in response to a control voltage (Vc) generated from a computer. With the total (acid + base) flow rate (FT) being kept constant, the base solution was merged with an acid solution, which was aspirated to the confluence point at a flow rate of FT - FB. Downstream, the relative transmittance of the mixed solution was measured at the maximum absorption wavelength of the base form of the indicator. Initially, a feedback-based control was applied, where the scan direction of Vc was reversed from upward to downward, and vice versa, whenever the transition of the indicator at the equivalence point (EP) was sensed. Next, the scan range of V. was further limited to the range just around EP by using fixed triangular waves. These processes avoided scanning in a range of no interest. Thus, an unprecedentedly high throughput rate (maximally 34 titrations per minute, corresponding to 1.76 s per titration) was realized with reasonable precision (RSD < 0.5%).
    Analytical Sciences 06/2005; 21(6):615-8. · 1.57 Impact Factor
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    ABSTRACT: The chloroform/water distribution coefficients (K(D)) of sixteen diazine compounds were determined by a stepwise flow ratiometry. An aqueous solution of analyte was delivered and merged with chloroform. The flow rate ratio of both the phases was varied stepwise under a constant total (chloroform+aqueous) flow rate. The analyte was extracted to chloroform while both the phases, which were segmented by each other, were passing through an extraction coil. The segmented stream was then led to a UV/Vis detector directly without phase-separation. The absorbance of the chloroform and aqueous phases (A(o) and A(a), respectively) was each measured at the maximum absorption wavelength of the analyte. The plots of A(-1) against R(f), (AR(f))(-1) against R(f)(-1), and AR(f) against A gave straight lines, where A was A(o), A(a) or the sum of them (A(S)). The K(D) of the analyte was calculated from the slopes and intercepts of the plots. The log K(D) values obtained for the analytes (-0.5-1.4) were agreed well with the values measured by a shake-flask method. The present method is simple, rapid (5 min/determination) and applicable to the volatile compounds with reasonable precision (standard deviation of log K(D)<0.07).
    CHEMICAL & PHARMACEUTICAL BULLETIN 04/2005; 53(4):374-7. · 1.56 Impact Factor
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    ABSTRACT: We propose a method for the determination of acid dissociation constants based on the rapid detection of the equivalence point (EP) by feedback-based flow ratiometry and the subsequent estimation of the half equivalence point (EP(1/2)). The titrant (e.g., NaOH) flow rate F(B) was varied in response to a control voltage V(c) from a controller, while the titrand (e.g., CH(3)COOH) flow rate F(A) was held constant. The pH of the mixed solution was monitored downstream from the confluence point of the solutions following a knotted tubular mixer. Initially, V(c) was increased linearly. At the instance the detector sensed EP, the ramp direction of V(c) changed downward. The pH increased further because of the lag time between the mixing of solutions and the sensing of pH. Following the pH maximum, the pH decreased. The EP was sensed again in this downward scan. The V(c) that gives EP(1/2) was computed from the V(c) just at the time of the EP detection. The V(c) was held constant at this level for 18s, and the plateau pH value thus obtained was taken to be the pK(a) of the analyte subject to activity corrections. Studies on the dependence of the pK(a) on the ionic strength or dielectric constant of the solution were conducted in an automated fashion by delivering NaCl solution or acetonitrile through an additional channel. Satisfactory results were obtained with good throughput (53s per determination) and precision (R.S.D. approximately 0.3%) for various acids.
    Talanta 01/2005; 64(5):1169-74. · 3.50 Impact Factor
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    ABSTRACT: To analyze the log P(sol/w) values (sol: n-octanol or chloroform, w: water) in the framework of the molecular orbital (MO) procedure, we selected solute descriptors such as the solvation energy difference between aqueous and organic solvent phases and the "surface" area of solute molecules to which water molecules are accessible. The solvation energy of solute molecules in their minimum free-energy conformation was calculated using the ab initio self-consistent reaction field-MO method with the conductor-like screening model. The experimentally measured log P(sol/w) value of various solutes except for those of amphiprotics was shown to be analyzable reasonably well by the MO model with additional descriptors for the hydrogen-bonding patterns in the solute-solvent interactions.
    Journal of Pharmaceutical Sciences 12/2004; 93(11):2681-97. · 3.13 Impact Factor
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    ABSTRACT: The mechanisms of retention of two recent stationary phases of interest in lipophilicity measurements, namely of the silica-based Discovery-RP-Amide-C16 phase and the polymer-based ODP-50-4B phase, were assessed and compared. A set of 41 model solutes and drugs with well-defined solvatochromic parameters were selected to allow a broad distribution of property spaces. The chromatographic results showed that, under the conditions of study, the lipophilicity index log kw obtained with the former stationary phase was more closely related to experimental log Poct values than was log kw obtained with the ODP-50-4B phase. Linear solvation/free-energy relationship (LSER) analyses showed that the retention mechanisms of the two stationary phases are different, retention on the Discovery-RP-Amide-C16 phase and partitioning in octan-1-ol/H2O being controlled by the same balance of intermolecular forces (Van der Waals volume Vw, H-bond acceptor basicity β, and dipolarity/polarizability π*).
    Helvetica Chimica Acta 11/2004; 87(11):2866 - 2876. · 1.38 Impact Factor
  • Hideji Tanaka, Takahiro Tachibana
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    ABSTRACT: Acid dissociation constants (Ka) were determined through the rapid detection of the half equivalence point (EP1/2) based on a feedback-based flow ratiometry. A titrand, delivered at a constant flow rate, was merged with a titrant, whose flow rate was varied in response to a control voltage (Vc) from a controller. Downstream, the pH of the mixed solution was monitored. Initially, Vc was increased linearly. At the instance that the detector sensed EP1/2, the ramp direction of Vc changed downward. When EP1/2 was sensed again, Vc was increased again. This series of process was repeated automatically. The pH at EP1/2 was regarded as being pKa of the analyte after an activity correction. Satisfactory results were obtained for different acids in various matrices with good precision (RSD approximately 3%) at a throughput rate of 56 s/determination.
    Analytical Sciences 07/2004; 20(6):979-81. · 1.57 Impact Factor
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    ABSTRACT: We applied the principle of feedback-based flow ratiometry, originally developed for continuous titrations, to the determination of acid dissociation constants (Ka). The titrant (NaOH) flow rate FB was varied in response to a control voltage Vc from a controller, while the total (titrant+titrand) flow rate FT was held constant. The titrand was aspirated to the flow system at the flow rate of FT−FB, and mixed with the titrant at the confluence point. Downstream, the pH of the mixed solution was measured with a glass electrode. Initially, Vc (thus FB) was ramped upward linearly. At the instant the detector sensed the half equivalence point, Eq1/2, where the buffer capacity is maximum, the algorithm reversed the ramp direction of Vc downwards. When Eq1/2 was sensed again, the algorithm reversed the ramp direction of Vc again, upwards. By repeating these processes automatically, time utilization efficiency of the procedure was improved by scanning Vc only in the range of interest. When the Vc scan range was thus constrained, the pH values corresponding to either a maximum or minimum in Vc, were equal to the pKa of the analyte. The pKa values thus obtained for various n-alkyl carboxylic acids and phosphoric acid agreed well with the literature. High throughput (ca. 26 s per determination) was attainable with reasonable precision (R.S.D.<3%).
    Analytica Chimica Acta 12/2003; 499:199-204. · 4.39 Impact Factor

Publication Stats

75 Citations
49.82 Total Impact Points

Institutions

  • 2001–2014
    • The University of Tokushima
      • • Graduate School of Pharmaceutical Sciences
      • • Faculty of Pharmaceutical Sciences
      • • Institute of Health Biosciences (HBS)
      Tokusima, Tokushima, Japan