Analytical Sciences
Online ISSN : 1348-2246
Print ISSN : 0910-6340
ISSN-L : 0910-6340
Volume 21 , Issue 6
Showing 1-26 articles out of 26 articles from the selected issue
Reviews
Original Papers
  • Hideji TANAKA, Tsutomu BABA
    2005 Volume 21 Issue 6 Pages 615-618
    Published: 2005
    Released: November 18, 2005
    JOURNALS FREE ACCESS
    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 Vc 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%).
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  • Emi SUENAGA, Hiroshi NAKAMURA
    2005 Volume 21 Issue 6 Pages 619-623
    Published: 2005
    Released: November 18, 2005
    JOURNALS FREE ACCESS
    Three staining methods using SYBR® Gold Nucleic Acid Gel Stain (SYBR Gold) as a fluorescent dye were evaluated for the agarose gel electrophoretic detection of DNA. The methods involve prestain, in-gel stain, and poststain methods. DNA markers and polymerase chain reaction (PCR) products obtained by minisatellite variant repeat-PCR (MVR-PCR) amplification in a D1S8 locus were used as model DNA and practical samples, respectively. Among the three methods tested under the usual electrophoretic conditions, a prestain method using a 10000-fold diluted SYBR Gold solution showed most excellent features regarding cost and rapidity to use with good stainability and resolution over loaded DNA amounts of about 98 ng to 300 ng. The prestain method was found to be applicable to the analysis of DNA in MVR-PCR products from a human hair root.
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  • Kazutoshi NOSE, Yoko NUNOME, Takaharu KONDO, Syuki ARAKI, Takao TSUDA
    2005 Volume 21 Issue 6 Pages 625-628
    Published: 2005
    Released: November 18, 2005
    JOURNALS FREE ACCESS
    We investigated whether methane, ethylene and ethane gas can be detected in gas emanating from human skin, which is called skin gas. Skin gas was collected with a homemade stainless-steel trap system, which was cooled with liquid nitrogen, and analyzed with a gas chromatograph fitted with a flame ionization detector (FID). Skin-gas samples were obtained by covering a hand for 30 min with a polyfluorovinyl bag in which pure helium gas was introduced. The bag, the trap system and GC were set up online to avoid any contamination by air. Methane, ethylene and ethane in skin gas were successfully collected at an average amount emanated for 30 min (from ten subjects) of 150 ± 63, 20 ± 11 and 17 ± 8 [mean ± SD] pg/cm2, respectively.
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  • Yukio KANDA, Masafumi TAIRA, Kazuhiko CHIMURA, Tomoyuki TAKANO, Motoak ...
    2005 Volume 21 Issue 6 Pages 629-634
    Published: 2005
    Released: November 18, 2005
    JOURNALS FREE ACCESS
    A reliable and convenient system to generate accurate and stable standard gas mixtures of various atmospheric compounds at parts-per-billion levels has been developed. The system is of simple design; the generator is a coil consisting of an inner tube of microporous polytetrafuluoroethylene (PTFE) membrane tubing and an outer tube of silicone tubing. An aqueous solution of the given compound continuously flows through the inner microporous tube and the purge gas flows through the annulus between the inner and outer tubes. In addition to the generation of gas mixtures based on Henry's law, the proposed flow-type system offers generation based on chemical reactions, leading to a distinct advantage of the availability of continuous sources of various compounds. The generation system was tested for preparing standard gas mixtures of HCHO and H2O2 on the basis of Henry's law, and those of HNO2, NO, and SO2 on the basis of chemical reactions. A stable generation of the desired low concentrations of various kinds of gas mixtures can be readily achieved by adjusting the concentration of the solution without the use of high-dilution flow.
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  • Hisao YAMASHIGE, Shuji MATSUO, Tsutomu KURISAKI, Rupert C. C. PERERA, ...
    2005 Volume 21 Issue 6 Pages 635-639
    Published: 2005
    Released: November 18, 2005
    JOURNALS FREE ACCESS
    This study investigated the protonation of nitrogen atoms in porphyrins with meso-phenyl p-substituted by an electron-withdrawing group using N 1s X-ray photoelectron spectroscopy (XPS), the N K X-ray absorption near-edge structure (XANES), and the discrete variational (DV)-Xα molecular orbital (MO) method. Both tetraphenylporphyrin (TPP) and tetrakis(p-sulfonatophenyl)porphyrin (TSPP) have a single structure: the former has two protonated and two non-protonated N atoms in the porphine ring; the latter has four protonated N atoms in the porphine ring. In contrast, a combination of XPS, XANES, and DV-Xα MO calculations shows that tetrakis(p-carboxyphenyl)porphyrin (TCPP) has a dual structure: one structure has two protonated and two non-protonated N atoms; the other has four protonated N atoms. Furthermore, this result was also considered based on the protonation constants of N atoms in the porphyrins. The correlation between the strength of electron-withdrawing groups and protonation to N atoms in porphyrins can be described using the spectral patterns of the N 1s XPS and N K XANES spectra.
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  • Li-Fang HE, Dan-Li LIN, Yao-Qun LI
    2005 Volume 21 Issue 6 Pages 641-645
    Published: 2005
    Released: November 18, 2005
    JOURNALS FREE ACCESS
    The use of micellar media in constant-energy synchronous fluorescence spectrometry has been proposed. The influence of some aqueous micellar systems on the determination of pyrene, perylene and benzo[a]pyrene has been investigated. The presence of these micellar systems allows their determination in aqueous media, thus avoiding the use of an organic solvent, and greatly enhances the fluorescence signals. The combination of a constant-energy synchronous scanning technique and a micellar system provided a single spectrum for the simultaneous identification and quantitative determination of the three polycyclic aromatic hydrocarbons (PAHs). Further there was no energy transfer among them, making the measurement simple and fast. A constant-energy difference of 2800 cm-1 was selected. The analytical characteristics of the proposed method in the presence of anionic micelles of sodium dodecylsulfate (SDS) were studied. The detection limits were at a level of ng ml-1. Analysis of water samples from two different origins spiked with known amount of pyrene, perylene and benzo[a]pyrene also gave satisfactory results, and total average recoveries were greater than 97.1%.
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  • Kousuke ATSUMI, Tomoharu MINAMI, Joichi UEDA
    2005 Volume 21 Issue 6 Pages 647-649
    Published: 2005
    Released: November 18, 2005
    JOURNALS FREE ACCESS
    A coprecipitation method with ytterbium hydroxide was studied for the determination of cadmium in water samples by graphite-furnace atomic absorption spectrometry. Up to 40 ng of cadmium in water samples was quantitatively coprecipitated with ytterbium hydroxide at pH 8.0 - 11.2. The concentration factor was 100 fold. The coprecipitated cadmium was sensitively determined without any influence of ytterbium and the calibration curve was linear from 0.1 to 4 ng/mL of cadmium. The detection limit (signal/noise = 2) was 2.9 pg/mL in 100 mL of the initial sample solution. Twenty-nine diverse ions tested did not interfere with the determination in at least a 10000-fold mass ratio to cadmium. The proposed method was successfully applied to the determination of cadmium in spring water.
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  • Shuzhen ZHANG, Anxiang LU, Fang HAN, Xiao-quan SHAN
    2005 Volume 21 Issue 6 Pages 651-654
    Published: 2005
    Released: November 18, 2005
    JOURNALS FREE ACCESS
    A rapid separation and preconcentration method was developed for the determination of trace metals Cu, Zn, Cd, and Pb in seawater using a minicolumn packed with thiol cotton fiber (TCF) coupled with inductively coupled plasma mass spectrometry (ICP-MS). Preconcentration parameters, such as seawater sample volume and flow rate and eluent hydrochloric acid concentration, volume and flow rate, were optimized. Under the optimized conditions, trace metals Cu, Zn, Cd, and Pb in seawater can be determined with no interference from saline matrices. When a sample volume of 1500 ml and a sample flow rate of 15 ml min-1 were used, the preconcentration factor of 1500 and RSD value of < 7% at ng ml-1 were achieved. The accuracy of the recommended method was verified by the analysis of certified reference materials.
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  • Meissam NOROOZIFAR, Mozhgan KHORASANI-MOTLAGH, Kambiz AKHAVAN
    2005 Volume 21 Issue 6 Pages 655-659
    Published: 2005
    Released: November 18, 2005
    JOURNALS FREE ACCESS
    A new and simple flow injection method followed by atomic absorption spectrometry has been developed for the indirect determination of ascorbic acid. The proposed method is based on oxidation of ascorbic acid to dehydroascorbic acid using a solid-phase manganese dioxide (30% m/m suspended on silica gel beads) reactor. The flow of the sample through the column reduces the MnO2 to Mn(II) in an acidic carrier stream of 6.3 mM HNO3 (pH 2.2) with flow rate of 4.0 ml/min at room temperature; Mn(II) is measured by atomic absorption spectrometry. The absorbance of Mn(II) is proportional to the concentration of ascorbic acid in the sample. The calibration curve was linear up to 30 mg/L, with a detection limit of 0.2 mg/L for a 220 µL injected sample volume. The developed procedure was found to be suitable for the determination of AsA in pharmaceuticals and foods with a relative standard deviation better than 1.09% and a sampling rate of about 95 h-1. The results exhibit no interference from the presence of large amounts of organic compounds. The reliability of the method was established by parallel determination against the 2,6-dichlorophenol-indophenol methods.
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  • Mohammad POURHOSSEIN, Mohammad K. AMINI, Morteza TALEBI
    2005 Volume 21 Issue 6 Pages 661-665
    Published: 2005
    Released: November 18, 2005
    JOURNALS FREE ACCESS
    A simple flow injection spectrophotometric method for the determination of nitrite is described. Nitrite injected into the flow system reacts with thiourea in acidic medium and the generated thiocyanate ion reacts with Fe(III) in the reagent solution to produce a highly colored product. The influences of chemical and physical parameters including reagent concentrations, sample volume injected, flow rates of the carrier and reagent solutions, reaction coil length and reaction temperature, were studied and optimum values of these parameters were established. Under the optimum conditions, the calibration curve for nitrite was linear over the concentration range 0.36 - 90 µg ml-1 without preconcentration and over the range 3.8 - 500 ng ml-1 with a simple online preconcentration step using an anion exchange column. The corresponding detection limits were 0.36 µg ml-1 and 3.8 ng ml-1, respectively. Up to 25 samples can be analyzed per hour, with an average relative standard deviation of ≤ 1.2%. Interferences by various foreign ions were studied and the method was applied to the determination of nitrite in water and spiked water samples.
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  • Andrew O. SIMM, Sarah WARD-JONES, Craig E. BANKS, Richard G. COMPTON
    2005 Volume 21 Issue 6 Pages 667-671
    Published: 2005
    Released: November 18, 2005
    JOURNALS FREE ACCESS
    A new method is proposed for the simple preparation of random silver micro and nano-electrode arrays. This employs acoustic streaming directed at a glassy carbon surface to “mechanically” attach particles from a suspension of metal colloidal or other small particles. The particles tend to adhere to the substrate at points of imperfection such as scratches, crevices etc. These arrays are compared with arrays formed by the electro-deposition of silver at a glassy carbon substrate, with the silver being partially stripped off, leaving a stable micro and nanoparticle array on the surface. Both surfaces are characterised using optical and atomic force microscopy. The two types of electrodes are evaluated to their analytical utility via the electrochemical reduction of halothane and their performance compared with that of a silver macroelectrode. A notable increase in sensitivity and peak current is observed.
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  • Saad S. M. HASSAN, M. S. EL-SHAHAWI, A. M. OTHMAN, M. A. MOSAAD
    2005 Volume 21 Issue 6 Pages 673-678
    Published: 2005
    Released: November 18, 2005
    JOURNALS FREE ACCESS
    The construction and performance characteristics of a novel chromate ion-selective membrane sensor are described and used for determining chromium(III) and chromium(VI) ions. The sensor is based on the use of a rhodamine-B chromate ion-associate complex as an electroactive material in a poly(vinyl chloride) membrane plasticized with o-nitrophenyloctyl ether as a solvent mediator. In a phosphate buffer solution of pH 6 - 7, the sensor displays a stable, reproducible and linear potential response over the concentration range of 1 × 10-1 - 5 × 10-6 mol l-1 with an anionic Nernstian slope of 30.8 ± 0.5 mV decade-1 and a detection limit of 1 × 10-6 mol l-1 Cr(VI). High selectivity for Cr(VI) is offered over many common anions (e.g., I-, Br-, Cl-, IO4-, CN-, acetate, oxalate, citrate, sulfate, phosphate, thiosulfate, selenite, nitrate) and cations (e.g., Ag+, Ca2+, Sr2+, Co2+, Ni2+, Cu2+, Mn2+, Fe2+, Zn2+, Cd2+, Al3+, Cr3+). The sensor is used for determining Cr(VI) and/or Cr(III) ions in separate or mixed solutions after the oxidation of Cr(III) into Cr(VI) with H2O2. As low as 0.2 µg ml-1 of chromium is determined with a precision of ±1.2%. The chromium contents of some wastewater samples were accurately assessed, and the results agreed fairly well with data obtained by atomic absorption spectrometry.
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  • Liu YANG, Wanzhi WEI, Jianjun XIA, Han TAO, Pinghua YANG
    2005 Volume 21 Issue 6 Pages 679-684
    Published: 2005
    Released: November 18, 2005
    JOURNALS FREE ACCESS
    Electrochemical impendence spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were performed to investigate the barrier properties and electron transfer of derivatized thiol self-assembled monolayers (SAMs) on gold in the presence of surfactants. The thiol derivatives used included 2-mercaptoethanesulfonic acid (MES), 2-mercaptoacetic acid (MAA), and N-acetyl-L-cysteine (NAC). A simple equivalent circuit was derived to fit the impedance spectra very well. The negative redox probe [Fe(CN)6]3-/4- was selected to indicate the electron-transfer efficiency on the interface of the studied electrodes. It was found that by changing the surface structure of SAMs, different surfactants could regulate the barrier properties and electron-transfer efficiency in different ways. A positively charged surfactant lowered the electrostatic repulsion between the negative redox probe and negatively charged surface groups of a monolayer, while enhancing the reversibility of electron transfer by virtue of increasing the redox probe concentration within the electric double-layer region. A neutral surfactant showed no significant effect, while a negative surfactant hindered the access and reaction of redox probe by electrostatic repulsion of same-sign charges.
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  • Gültekin GöKÇE, Zehra DURMUS, Habibe TEZCAN, Esma KIL ...
    2005 Volume 21 Issue 6 Pages 685-688
    Published: 2005
    Released: November 18, 2005
    JOURNALS FREE ACCESS
    Cyclic voltammetric (CV) and chronoamperometric (CA) behaviors of 1,3,5-triphenylformazan (TPF), 3-(p-nitrophenyl)-1,5-diphenylformazan (PNF) and 3-(m-nitrophenyl)-1,5-diphenylformazan (MNF) were studied in dimethyl sulfoxide medium. TPF was found to give a single sharp cathodic CV peak corresponding to a gain of one-electron per molecule. The diffusion coefficient and the number of electrons transferred were calculated using the Baranski equation with the CV-data obtained by an ultramicroelectrode. Standard rate constants for the reduction were calculated by the Klingler-Kochi technique. The electrochemical data obtained support the mechanism proposed by Umemoto.
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  • Reza Emamali SABZI, Mohammad Hussein POURNAGHI-AZAR
    2005 Volume 21 Issue 6 Pages 689-692
    Published: 2005
    Released: November 18, 2005
    JOURNALS FREE ACCESS
    An electrochemically prepared thin film of cobalt pentacyanonitrosylferrate (GC/CoPCNF) was used as a surface modifier for glassy carbon electrodes. The oxidation of ascorbic acid on a glassy carbon electrode modified with GC/CoPCNF as a working electrode was studied using cyclic voltammetry, rotating disk electrode (RDE) voltammetry and chronoamperometry in a 0.25 M KNO3 + 0.25 M phosphate buffer (pH 7) solution. The glassy carbon modified with CoPCNF showed good electrocatalytic activity toward ascorbic acid oxidation. The kinetics of the catalytic reaction was investigated, and the average value of the rate constant (k) for the catalytic reaction and the diffusion coefficient (D) were evaluated by different approaches for ascorbic acid, and were found to be 3.3 ± 0.3 × 102 M-1 s-1 and 3.2 ± 0.3 × 10-6 cm2 s-1, respectively.
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