Analytical Sciences
Online ISSN : 1348-2246
Print ISSN : 0910-6340
ISSN-L : 0910-6340
Volume 22 , Issue 8
Showing 1-21 articles out of 21 articles from the selected issue
Rapid Communications
Reviews
  • Katsumi HIROSE
    2006 Volume 22 Issue 8 Pages 1055-1063
    Published: 2006
    Released: August 09, 2006
    JOURNALS FREE ACCESS
    The recent development of the chemical speciation of trace metals in seawater is described. The speciation studies reveal that metal ion complexation is one of the most important processes in seawater; especially, most bioactive trace metals, such as Fe(III) and Cu, exist as complexes with ligands in dissolved organic matter. The organic ligands in seawater are characterized with metal ions selected by the HSAB concept. A strong organic ligand, which originates from marine microorganisms, is classified as a hard base including carboxylates. The free organic ligand concentrations in seawater are buffered by complexation with excess amounts of Ca and Mg in seawater. The chemical equilibrium model suggested that the concentrations of bioactive free metal ions are at an optimal level to activities of marine microorganisms. For chemical speciation, it is important to have a better understanding of the ecological roles of trace metals in seawater.
    Download PDF (98K)
Original Papers
  • Takashi MASADOME, Kensuke YADA, Shin-ichi WAKIDA
    2006 Volume 22 Issue 8 Pages 1065-1069
    Published: 2006
    Released: August 09, 2006
    JOURNALS FREE ACCESS
    A cationic surfactant ion-selective field-effect transistor (cationic surfactant-ISFET) has been developed based on the tetraphenylborate derivative known as sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate. The cationic surfactant-ISFET shows an almost Nernstian response to tetradecyldimethylbenzylammonium chloride (Zephiramine) over a concentration range between 1.0 × 10-6 M and 1.0 × 10-3 M, with a slope of 58.5 ± 1.7 mV/decade. The cationic surfactant-ISFET can be used over a range of pH values, between pH 3 and 9. The cationic surfactant-ISFET shows excellent selectivity for Zephiramine over small inorganic cations, but shows similar selectivity for other cationic surfactants, such as hexadecyltrimethylammonium and stearyltrimethylammonium ions. A microfluidic polymer chip was integrated with the cationic surfactant-ISFET, and this was fabricated using polystyrene plates and stainless wires as a template for the channel. Cationic surfactant-ISFETs used in a batch system and microchips integrated with cationic surfactant-ISFETs showed very similar performance in terms of low detection limits, slope sensitivity and the stability of the potential response. The microfluidic polymer chip was then applied to the determination of cationic surfactants in dental rinses.
    Download PDF (81K)
  • Yun-Chun LIU, Shi-Qiang CUI, Zhou-Sheng YANG
    2006 Volume 22 Issue 8 Pages 1071-1074
    Published: 2006
    Released: August 09, 2006
    JOURNALS FREE ACCESS
    DNA was immobilized on glassy carbon electrodes to fabricate DNA-modified electrodes. The direct electron transfer of horse heart cytochrome c on DNA-modified glassy carbon electrode was achieved. A pair of well-defined redox peaks of cytochrome c appeared at Epc = -0.017 V and Epa = 0.009 V (vs. Ag/AgCl) in 10 mM phosphate buffer solution (pH 7.0) at a scan rate of 50 mV/s. The electron transfer coefficient (α) and the standard rate constant of the surface reaction (Ks) of cytochrome c on DNA-modified electrodes could be estimated to be 0.87 and 34.52 s-1, respectively. The DNA-modified glassy carbon electrode could be applied to detect cytochrome c by means of differential pulse voltammetry (DPV). The cathodic peak current was proportional to the quantity of cytochrome c in the range of 4.0 × 10-6 M to 1.2 × 10-5 M. The correlation coefficient is 0.996, and with the detection limit was 1.0 × 10-6 M (three times the ratio of signal to noise, S/N = 3).
    Download PDF (80K)
  • Mohammad Reza YAFTIAN, Saeed RAYATI, Daryoush EMADI, Dominique MATT
    2006 Volume 22 Issue 8 Pages 1075-1078
    Published: 2006
    Released: August 09, 2006
    JOURNALS FREE ACCESS
    The preparation of a lead-selective electrode based on 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis-(diphenylphosphinoylmethoxy)calix[4]arene (1) as an ionophore is reported. The plasticized PVC membrane containing 30% PVC, 57% ortho-nitrophenyloctylether (NPOE), 4% sodium tetraphenylborate (NaTPB) and 9% ionophore 1 was directly coated on a graphite electrode. It exhibits a nearly Nernstian slope of 28.0 ± 0.2 mV decade-1 over a concentration range of 1 × 10-5 - 1 × 10-2 mol dm-3 with a detection limit of 1.4 × 10-6 mol dm-3. The response time of the electrode was found to be ca. 17 s. The potential of the sensor was independent of the pH variation in the range 3.5 - 5.0. The selectivity of the electrode performance towards lead ions over Th4+, La3+, Sm3+, Dy3+, Y3+, Ca2+, Sr2+, Cd2+, Mn2+, Zn2+, Ni2+, Co2+, NH4+ Ag+, Li+, Na+ and K+ ions was investigated. The prepared electrode was used successfully as an indicator electrode for a potentiometric titration of a lead solution using a standard solution of EDTA. The applicability of the sensor for Pb2+ measurements in various synthetic water samples spiked with lead nitrate was also checked.
    Download PDF (83K)
  • Yi Na JIANG, Hong Qun LUO, Nian Bing LI
    2006 Volume 22 Issue 8 Pages 1079-1083
    Published: 2006
    Released: August 09, 2006
    JOURNALS FREE ACCESS
    2,5-Dimercapto-1,3,4-thiadiazol (DMTD) can bind on the surface of a gold electrode through the strong gold-sulfur interaction. The fabrication and electrochemical characteristics of the DMTD self-assembled monolayer (SAM)-modified gold electrode were investigated. The DMTD SAM electrode exhibited a significantly increased sensitivity. Cu(II) was accumulated in phosphate buffer (pH 4.6) at a potential of -0.6 V (vs. Ag/AgCl) for 40 s and then determined by anodic stripping voltammetry (ASV) in copper-free phosphate buffer (pH 5.0). The effects of various parameters, such as the pH values of the preconcentration solution and measurement solution, the accumulation potential, and the accumulation time, were investigated. Under the optimum conditions, a linear calibration graph was obtained in the concentration range of 8.0 × 10-6 to 8.0 × 10-5 mol l-1 with a correlation coefficient of 0.9978. The relative standard deviations for eight successive determinations were 4.3 and 2.9% for 1.0 × 10-5 and 2.0 × 10-5 mol l-1 Cu(II), respectively. The detection limit (three times signal to noise) was 4.0 × 10-7 mol l-1. The proposed voltammetric method was utilized successfully to detect the concentration of Cu(II) ions in tap water samples.
    Download PDF (95K)
  • Keisuke MORITA, Emiko KANEKO
    2006 Volume 22 Issue 8 Pages 1085-1089
    Published: 2006
    Released: August 09, 2006
    JOURNALS FREE ACCESS
    In this study, a simple and sensitive method for the determination of arsenic in water samples was developed. The method is based on the formation of micro particles of Ethyl Violet and molybdoarsenate, which gives an apparently homogeneous blue color to the solution. The absorption of the excess dye gradually decreases due to its conversion to a colorless carbinol species under strongly acidic conditions. Consequently, the sufficiently low reagent blank enables the spectrophotometric determination of arsenic with the detection limit of 4 µg l-1. The coefficient of variation for the spectrophotometry at 50 µg l-1 was 3.5% (n = 5). Furthermore, it is possible to detect concentrations as low as 10 µg l-1 of arsenic visually. Our method will be useful as a simple, rapid, and cost-effective field test of arsenic, requiring no complex apparatus or skilled laboratory support.
    Download PDF (124K)
  • Bin QI, Akinori TAKAMI, Shiro HATAKEYAMA
    2006 Volume 22 Issue 8 Pages 1091-1093
    Published: 2006
    Released: August 09, 2006
    JOURNALS FREE ACCESS
    A new method is proposed to determine the calibration factor (CF) of methyl and ethyl peroxy radicals in a chemical amplifier. The radical source comes from the reactions of excess methane and ethane, respectively, with known concentrations of OH radicals generated by the photolysis of water vapor at 184.9 nm in air in a flow tube. This yields a mixed radical source with equal amounts of HO2 and RO2 (R = CH3, C2H5). The CF for RO2 can be derived from the CF for HO2 and an average CF for the mixed radicals. The reliability of the method was evaluated by comparing the CF ratios of RO2 to HO2 obtained from both the experiments and theoretical calculations.
    Download PDF (59K)
  • Amir WASEEM, Mohammad YAQOOB, Abdul NABI
    2006 Volume 22 Issue 8 Pages 1095-1098
    Published: 2006
    Released: August 09, 2006
    JOURNALS FREE ACCESS
    A flow-injection method is reported for the determination of thyroxine based on its enhancement effect on the tris(2,2′-bipyridyl)ruthenium(III) chemiluminescence reaction in the presence of NADH using immobilized alcohol dehydrogenase purified from baker yeast. The limit of detection (3 σ blank) was 5.0 × 10-8 M with a sample throughput of 80 h-1. The calibration graph was linear over the range 0.5 - 10 × 10-7 M (r2 = 0.9988) with the relative standard deviation in the range 1.4 - 3.5% (n = 4). The effect of common excipients used in pharmaceutical preparations, some organic compounds and metal ions was studied. The method was applied to pharmaceutical thyroxine tablets, and the obtained results were not significantly different from the amount quoted.
    Download PDF (83K)
  • Xiaochuan WANG, Xiuhan YANG, Xiangmin ZHANG
    2006 Volume 22 Issue 8 Pages 1099-1104
    Published: 2006
    Released: August 09, 2006
    JOURNALS FREE ACCESS
    A microfluidic solid phase extraction (SPE) array for sample enrichment was prepared by a simple method, a hot embossing technique. Five fused-silica capillaries (250 µm i.d., 380 µm o.d.) were partly embedded parallel in a polymethyl methacrylate (PMMA) microchip to serve as the extraction channels. Within each of the channels, a 2-mm-long monolithic porous polymer was prepared by in-situ photoinitiated polymerization. This then acted as the frit for packing of the extraction materials (octadecylsilica beads, ODS). By defining the light-exposure window on the channels, one can easily control the length and location of the polymer frits and the ODS beads can be packed at the desired location. With this method, solid phase extraction channels for microfluidic use can be easily prepared without complex fabrication of microstructures. Several SPE channels can be conveniently made in one microchip since the frits can be prepared in different channels through one polymerization; packing of the different channels can also be performed simultaneously. With the use of dilute ephedrine solutions, the sample loading capacity, linearity, and reproducibility were characterized. Coupled with the fast capillary electrophoresis separation, this microchip SPE array was applied for the detection of ephedrines in human urine.
    Download PDF (115K)
  • R. K. DEY, Usha JHA, A. C. SINGH, S. SAMAL, Alok R. RAY
    2006 Volume 22 Issue 8 Pages 1105-1110
    Published: 2006
    Released: August 09, 2006
    JOURNALS FREE ACCESS
    Two new chelating materials (Si-DDE-o-HB, and Si-DDS-o-HB) were synthesized by modifying the activated silica gel phase with Schiff bases of 4,4′-diaminodiphenylether (DDE)/4,4′-diaminodiphenylsulfone (DDS) and o-hydroxybenzaldehyde (o-HB). The synthesized materials were characterized by FTIR and BET surface area measurement techniques. The extraction of metal ions such as Zn2+, Mn2+ and Cr3+ by the chelating material Si-DDE-o-HB was found to be higher than that by Si-DDS-o-HB. The order of metal sorption was found to be Zn2+ > Mn2+ > Cr3+. The correlation coefficients for Freundlich and Langmuir adsorption isotherms were compared for the sorption of Zn2+ onto the chelating material. The loading and elution of the metal ion solution was examined at optimum pH 7.5 and 0.5 cm3 min-1 flow rate of the solution using a column technique. The preconcentration factor for the elution of Zn2+ using dilute HNO3 was found to be 66.2 with a breakthrough volume of 15 cm3. The data obtained for the preconcentration of Zn2+ by the column technique suggested that the material Si-DDE-o-HB can find industrial applications.
    Download PDF (103K)
  • Hong-Ping XIE, Jian-Hui JIANG, Ze-Qin CHEN, Guo-Li SHEN, Ru-Qin YU
    2006 Volume 22 Issue 8 Pages 1111-1116
    Published: 2006
    Released: August 09, 2006
    JOURNALS FREE ACCESS
    Some raw materials that have different places of production for the plant sources of the drugs Astragalus membranaceus and ginseng have been studied, based on their near-infrared reflectance spectra. The experimentally recorded spectra represent heavily ill-posed and highly correlative data sets. Three related methods, i.e. the Fisher linear discriminant analysis (FLDA), the ridge-type linear discriminant analysis (RLDA) and a newly proposed penalized ridge-type linear discriminant analysis (PRLDA), have been investigated. FLDA over-fits for the training objects of the two data sets to a high extent and is unstable for the predictive objects of the two data sets. RLDA shows obvious improvement in terms of over-fitting and unstability, but the stability for the predictive objects of the two data sets is too sensitive to their ridge-type penalized weights, tending to produce erroneous discrimination results. The proposed PRLDA can circumvent the two aforementioned problems with a large domain of penalized weights for correct discriminant analysis of the two data sets studied. The combination of the PRLDA method and near infrared reflectance spectroscopy can be adapted for the discrimination of the production places of plant sources of these drugs.
    Download PDF (107K)
Notes
Announcements
Errata
feedback
Top