Vol. 59 No. 8
A new sampling system of gas- and particle-phase polycyclic aromatic hydrocarbons (PAHs) in ambient air is proposed. The system is composed of a commercially available multi-nozzle cascade impact sampler for collecting particles less than 10 μm and a newlydesigned glass cartridge (35 mm inner diameter) packed with 5.0 g of a styrene-divinylbenzene copolymer resin adsorbent (XAD-2) for collecting gas-phase PAHs at a flow rate of 20 L/min. A rapid sample preparation for the analysis of PAHs in XAD-2 resin by ultrasonic extraction was also studied. The recovery rates of selected PAHs, i.e. phenanthrene (PHEN), antrathene (ANT), fluorantene (FL), pyrene (PY), benzo[a]pyrene (BaP), benzo[k]fluoranthene (BkF), benzo[ghi]perylene (BghiP), and indeno[1,2,3-cd]pyrene (IP) after the pretreatment ranged from 80 to 100%. More than 95% of the PAHs were extracted from XAD-2 by ultrasonication twice for 20 min with dichloromethane. The newlydeveloped cartridge had more than 95% collection efficiencies of the gas-phase PAHs (PHEN, ANT, FL and PY) in both the summer and winter seasons. Storage at −30°C for 4 weeks did not have an adverse effect on the gas-phase PAHs collected with the cartridge. The application of the new sampling system to a field observation at a tower with a height of 12 m in a small forest at Field Museum Tama Hills revealed that the concentrations of the gas-phase PAHs at the lower level of the tower were lower than those at the upper level of the tower. However, there were no changes in the concentrations of the particle-phase PAHs between at the upper and lower levels. These results suggested that the forest filter effects for the gas-phase PAHs might be higher than those for the particle-phase PAHs.
Simple differential determinations of arsenic(III) and arsenic(V) in environmental water have been developed based on the selective coprecipitation of arsenic(V) with barium sulfate, followed by a tristimulus colorimetric method. Arsenic(V) coprecipitation with barium sulfate occurred in solution, having an excess of barium ion over sulfate ion when barium sulfate was formed. The pH of solution is also a very important factor for arsenic(V) copreciotation. Arsenic(V) was quantitatively coprecipitated with barium sulfate in solutions at pH 3〜9, but arsenic(III) was not coprecipitated even at pH 3〜9. To 20 mL of the sample solution, which was put into a syringe, a sodium sulfate solution and a barium chloride solution were added successively to cause the coprecipitation of arsenic(V) with barium sulfate. After filtration, arsenic(III) in the filtrate was determined with tristimulus colorimetry. Another portion of the sample solution was used for the determination of total-arsenic [As(III) + As(V)]. The arsenic(V) concentration was obtained by calculating the difference between the total-arsenic and arsenic(III) concentrations. The established method was successfully applied to environmental water samples, such as brackish lake water samples to clarify the behavior of arsenic(III) and arsenic(V) in redox-sensitive water regions.
A pretreatment method for the speciation of dissolved phosphorus compounds in water samples is proposed. For a sample solution containing orthophosphate, organophosphorus compound, and polyphosphoric acid, a three-step procedure has been developed for the determination of each phosphorus compound. At first, orthophosphate was determined with a conventional molybdenum-blue method. Second, an organophosphorus compound was decomposed selectively to orthophosphate by five minutes of UV irradiation with using a 400 W low-pressure mercury lamp. Finaly, in the presence of sulfuric acid and photocatalytic TiO2, the organophosphorus compound and polyphosphoric acid were decomposed to orthophosphate by thirty-five minutes of UV irradiation. The orthophosphate concentration obtained for each step was successfully used to estimate the concentration of the orthophosphate, organophosphorus compound, and the polyphosphoric acid originally present. In addition, an investigation of the wavelength dependence of the decomposition efficiency with a colored glass filter, showed that the irradiation of 184.9 nm is important for photodecomposing an organophosphorus compound; that of 365 nm in the presence of photocatalytic TiO2 is important to photodecompose polyphosphoric acid. This new method should be effective as a pretreatment method for the speciation of dissolved phosphorus compounds.
Chemiluminescence (CL) in a luminol-catalyst-hydrogen peroxide system is generally considered as follows. Luminol is oxidized with hydrogen peroxide in the presence of a catalyst, such as metal ions in a basic solution, generating a 6-membered peroxide intermediate. The 6-membered peroxide intermediate produces the excited-state aminophthalate. When this excited state decays to the ground state, emission is produced. In this study, twenty eight kinds of Co(III) complexes were synthesized and the catalysis of Co(III) complexes in the CL reaction of luminol with hydrogen peroxide was examined. The Co(III) complexes were categorized into 5 groups on the basis of the structure of the complexes, and the catalysis was evaluated with a 2-pump flow injection analysis (FIA) device. The extremely large differences in the chemiluminescence intensities were observed depending on the ligands. Among the Co(III) complexes examined, [Co(NO2)(NH3)5]Cl2 and [Co(CO3)(NH3)4]Cl showed remarkable catalysis. Therefore, the development of a sensitive analysis of hydrogen peroxide with FIA was attempted. The detection limits (S/N = 3) and the linear ranges were estimated under the most suitable detection conditions. The detection limits were of 0.2 nM (2 fmol) and 5 nM (50 fmol) for [Co(NO2)(NH3)5]Cl2 and [Co(CO3)(NH3)4]Cl, respectively. The calibration curves were linear up to 10 μΜ for both of these Co(III) complexes. The influence of foreign ions was examined in order to apply to measurements of hydrogen peroxide in real samples. Hydrogen peroxide in river water was successfully determined using the present method.
A spectrophotometric method for the determination of copper(II) was established with N,N-Diethyl-p-phenylenediamine and thymoquinone. In the determination of copper(II), Beer’s law was obeyed in a concentration range of 1.0〜10 ng mL−1 of copper(II). The apparent molar absorptivity was 2.61 × 106 L mol−1 cm−1 at 552 nm. The relative standard deviation for five replicate determinations for 6.3 ng mL−1 was 1.81%. The proposed method is superior to the other catalytic methods of determination for copper(II) with regard to the liner range and the relative standard deviation. The recoveries of copper(II) from real samples (tap water and supplement tablet) were within 96〜103%.
A determination method of nitrate and nitrite in foodstuffs using ion chromatography (IC) equipped with an inline dialysis system is presented. The conditions of the inline dialysis system were optimized for the simultaneous extraction of nitrate and nitrite. Under the optimized conditions, the detection limits (S/N = 3) for nitrate and nitrite when injecting 20 μL with UV detection were 0.08 mg L−1 and 0.05 mg L−1, respectively. The linear range of both ions was over 3 orders of magnitude, from 0.1 mg L−1 to 20 mg L−1. The relative standard deviation (RSD, n = 10) for nitrate and nitrite in sausage was 2.43% and 1.57%, respectively. The inline dialysis system combined with IC was applied to the simultaneous determination of nitrate and nitrite in foodstuffs, such as ham and sausage, and was compared to the determined values obtained by a solid-phase extraction-IC method and an enzyme-reduction spectrometric method. Good correlations for both ions between the inline-dialysis-IC method and the enzyme reduction spectrometric method were obtained. However, the results of the solid-phase extraction-IC method and the inline-dialysis-IC method did not show a good correlation, because the matrices could not be removed very well, and interfered with measurements in the solid extraction – IC method. The present method will be useful for the determination of inorganic ions in food samples containing high-concentration matrixes.
γ-CD was chemically bonded on monolithic silica capillary columns via urethanization, and the separation of 12 pairs of enantiomeric dansyl amino acids (DNS-AAs) was examined in capillary LC. The reaction conditions and the operating conditions were examined prior to the application for the monolithic capillary columns. Twelve pairs of enantiomers were analyzed by using 10% acetonitrile in 50 mM ammonium acetate as the eluent; eight pairs of them were separated on a γ-CD-bonded monolithic silica capillary column (450 × 0.100 mm i.d.). In all cases, the L-form eluted earlier than the D-form. The monolithic silica capillary columns could achieve better resolution than the particle-packed columns.
A septum-free pyrolysis-gas chromatography (Py-GC) system equipped with a septum-free injector was developed, which was usable with an injection (conection between pyrolyzer and GC) temperature even at 400°C. Under ordinary Py-GC conditions with an injection temperature of 320°C, the peak intensities and their reproducibility of the main pyrolysis products of polystyrene obtained by this system were comparable to those by the conventional system. Moreover, Py-high temperature GC was constructed by using a thermally stable Dexile-type separation column under high-temperature conditions of around 400°C. Moreover, not only the injector, but also pyrolyzer-interface, column oven and detector were also operated at up to 400°C. By using the Py-high temperature GC system, considerably high boiling-point products, which cannot be detected by the conventional system, were observed in the pyrograms of polyethylene, polydimethylsiloxane and poly (methyl acrylate). Futhermore, high-boling point oligomeric acylates were also observed in the pyrogram of ultra violet cured acrylic resin observed under thermochemolysis conditions in the presence of tetramethylammonium hydroxide.
The structural change from PrPC to PrPSc of the prion protein is thought to relate to Cu2+ binding to the His residue. In this study, the binding abilities of 9 synthetic fragment peptides of human PrPC, 4 peptides containing 1 to 4 OP-repeat (OP-1 to OP-4) and 5 peptides including the His residue, to various metal ions was tested by a column-switch HPLC composed of a chelating column and a reverse-phase column. OP-4 binds to the Cu2+ chelating column, but not to the Mn2+ chelating column. These binding abilities are the same as results obtained by CD analysis. Interestingly, all peptides tested here except for OP-1 bound to a Cu2+ chelating column. In addition, OP-repeat also bound to Ni2+, Zn2+ and Co2+, but almost all other peptides did not bind to those metal ions. These results strongly support that the column switch HPLC used here is a conventional method to analyze the binding affinity of peptides to various metal ions. The results obtained here suggest that Cu2+ binding to His residues outside of OP-repeat participate in structural changing from PrPC to PrPSc.
Complex formation equilibrium of phenylalkylammonium ions (PAA+) with 18-crown-6 (18C6) has been analyzed by capillary zone electrophoresis (CZE). The electrophoretic mobility of PAA+ (μep') was measured by CZE in the presence of 18C6 in a migrating buffer, and the μep' values were used for equilibrium analysis. The μep' values decreased with increasing concentrations of 18C6, and 1 : 1 complex formation constants, K, were determined. The K values for PAA+ in an aqueous solution are comparable to literature data reported for the ammonium ion. The K values increased with a longer alkyl chain in PAA+, except for the benzylammonium ion. The results suggested the contribution of hydrophobicity in PAA+, as well as CH/π interactions for the benzylammonium ion. The K values also increased in mixed aqueous solvents with a decreased dielectric constant, which suggested the contribution of ion-dipole interaction in the complex formation reaction.
Some complexing agents and surfactants sensitize luminol chemiluminescence (CL) with Fe(III) or Fe(II) as a catalyst ; also the effect of the sensitizing reagents on the CL intensity was examined in sequential injection analysis (SIA). Solutions of luminol, H2O2 and a sample solution containing Fe(III) or Fe(II) were sequentially introduced into a holding coil, and the zones of the sucked solutions were immediately propelled to a CL detection cell ; the CL intensity was measured. In the case of the complexing agents as additives, tartrate and oxalate ions in the sample solution were most effective to improve the CL intensity. When surfactants were used as additives, the chemiluminescence was sensitized over the critical micelle concentrations of cationic cetyltrimethylammonium bromide and anionic sodium dodecylsulfate. Sensitization with the complexing agents and the surfactants in SIA are much more effective than in flow injection analysis. Since mixing of the sucked zones is not sufficient in SIA, the chemiluminescence would have been effectively sensitized.
In this work, we have developed glucose biosensors based on chemical amplification with glucose cycling between glucose oxidase (GOx) and glucose dehydrogenase (GDH) immobilized on a poly(dimethylsiloxane) (PDMS) layer. PDMS-coated platinum electrodes modified with GOx and GDH have been prepared from poly(L-lysine) (polymer backbone) and glutaraldehyde (cross-linking agent). The reduction currents of oxygen were amperometrically monitored by adding glucose. In the presence of NADH, D-glucono-δ-lactone generated by glucose oxidation with an enzyme reaction of GOx is reduced back to glucose by the enzyme reaction of GDH. Since the reproduced glucose acts as a substrate of GOx again, the current response for oxygen is amplified by oxygen consumption with GOx. The PDMS layer with selective permeability for oxygen was used to prevent interference from hydrogen peroxide produced by the GOx reaction and the others in biological samples. The current response was amplified around 10 times and appeared at a concentration as low as 1.0 μM by using the present system. The glucose concentration could be determined in 500-fold diluted human serum in the presence of 5.0 mM NADH.
A novel spectrophotometric method was established for the determination of chlorpromazine (CP) and other drugs with an o-sulfophenylfluorone-gallium(III) complex. In the determination of CP, Beer’s law is obeyed in the range of 0.08〜2.0 μg/mL. The molar absorptivity and the relative standard deviation were 1.2 × 105 dm3 mol−1 cm−1 and 2.5% (n = 5), respectivery. Moreover, the method was successfully applied to assays of CP and other drugs in pharmaceutical preparations. The proposed method should be useful for simple and sensitive determinations of CP and other drugs.