Enhanced chemiluminescence for trazodone trace analysis based on acidic permanganate oxidation in concurrent presence of rhodamine 6G.

A new sensitized chemiluminescence method by acidic permanganate oxidation was developed for the sensitive determination of trazodone. A fluorescent dye as used rhodamine 6G to increase a chemiluminescence intensity. Under optimum conditions, the liner range of the calibration curve was obtained for 1-5000 nmol/L. The limit of detection was calculated from 3σ of a blank was 0.23 nmol/L. The coexistent ions and substances had no interference with the chemiluminescence measurement. The chemiluminescence spectra were measured to elucidate a possible mechanism for the system. The present method was satisfactorily used in the determination of the drugs in pharmaceutical samples and animal serums.

Influence of Introduced Substituents on the Anion-selectivity of [14]Tetraazaannulene Complexes.

Nickel(II) complexes of [14]tetraazaannulene derivatives incorporating aromatic rings into their azaannulene framework were synthesized, and the anion-selectivity of the [14]tetraazaannulene nickel complexes 1 - 4 was evaluated by potentiometric measurements with solvent polymeric membrane electrodes. All of the [14]Tetraazaannulene nickel complexes, except 3, were found to exhibit high selectivity for the I(-) ion over the SCN(-) ion, although considerable interference of the ClO4(-) ion was observed in all 1 - 4 complexes. Concerning the anion-selectivities of 1 and 4, the incorporation of naphthalene rings into the azaannulene framework decreased not only the interference of the ClO4(-) ion but also the I(-) ion-selectivity over the SCN(-) ion. Comparison studies between the dibenzotetraaza[14]annulene nickel complexes 1 - 3 indicated that differences in the attached substituents of the [14]tetraazaannulene nickel complexes greatly influenced the ion-selectivity as ionophores. According to our computational results, the ionophoric properties of [14]tetraazaannulene nickel complexes 1 - 4 were influenced by their electrostatic properties rather than their topological properties.

Ion-selective electrodes based on L-tryptophan and L-tyrosine.

Novel ion-selective electrodes (ISEs) based on amino acids have been developed. L-Tryptophan and L-tyrosine, which are amino acids, are employed as ionophores for solvent polymeric membrane electrodes. The proposed ISEs show rapid Nernstian responses for the Cu(2+) ion over the concentration ranges of 3.0×10(-4)-1.0×10(-1) M. These ISEs exhibit comparatively good selectivity with respect to alkaline, alkaline earth, and some transition and heavy metal ions and the ammonium ion. The ISE based on tryptophan also indicates the Nernstian response for the benzylammonium ion.

A new solvent polymeric membrane electrode incorporating poly(N-isopropylacrylamide) as a polymer.

Here, we report on a new solvent polymeric membrane electrode incorporating thermoresponsive poly(N-isopropylacrylamide) (PIPA) as a polymer with the lower critical solution temperature (LCST) of ca. 32 °C. The response of the solvent polymeric membrane electrode to the ions changes at 25 and 40 °C. Pulsed NMR analyses demonstrated the novel effects of the LCST behaviour on the potentiometric polymeric membrane.

Gas-particle concentrations of atmospheric polycyclic aromatic hydrocarbons at an urban and a residential site in Osaka, Japan: effect of the formation of atmospherically stable layer on their temporal change.

A comparative study on atmospheric polycyclic aromatic hydrocarbons (PAHs) in particulate matter and the gaseous phase was performed at an urban and a residential site in Osaka, Japan, during 2005-2006. PAH concentrations at the urban site were found to be approximately twice higher than those at the residential site. At both sites, particulate PAH concentrations increased mainly in winter while the trends of temporal change in gaseous PAH concentrations were not clearly observed. The main sources of PAHs were estimated to be local traffic, e.g., diesel engines with catalytic converter. PAH concentrations did not significantly negatively correlate with ozone concentrations and meteorological parameters. Gas-particle partitioning coefficients of representative PAHs with low molecular weight (LMW) significantly negatively correlated with ambient temperature, showing that temporal change in the LMW PAH concentrations in PM could be attributable to the shift of their gas-particle distribution caused by the change in ambient temperature. For the first time, we studied the effect of the formation of atmospherically stable layer following an increase in PAH concentrations in Japan. At the urban site, PAHs showed a significant positive correlation with potential temperature gradients, indicating that temporal variability in PAH concentrations would be dominantly controlled by the formation of atmospherically stable layer in Osaka area.

Determination of sulfide with acidic permanganate chemiluminescence for development of deep-sea in-situ analyzers.

A new chemiluminescence method is proposed for the determination of sulfide in seawater based on the chemiluminescence reaction between sulfide and an acidic permanganate solution. 3-Cyclohexylaminopropanesulfonic acid was used as a chemiluminescence enhancer. By use of this method, 1-150 µM of sulfide could be determined in artificial seawater. The limit of detection was 0.17 µM sulfide. We investigated the effects of salinity, water temperature, and interfering chemicals such as heavy-metal ions and organic matter. In addition, natural seawater spiked with sulfide was analyzed. The results showed that the CL method could be applied to a deep-sea sulfide analyzer.

Pulsed NMR analysis of ion-selective electrode membranes.

A novel method for evaluation of ion-selective electrode membranes was reported with the proton spin-spin relaxation time T(2) by pulsed NMR. The proton spin-spin relaxation time T(2) measurements provided valuable information about properties of the whole membrane matrix. The softer potentiometric liquid membrane possessed a large fraction F(L) providing relatively longer T(2) value. Pulsed NMR method can quantify the degree of the plasticization of ion-selective electrode membranes.

A Cu2+ ion-selective fluoroionophore with dual off/on switches.

A new malonamide fluoroionophore possessing two pyrene moieties was synthesized. This bispyrene exhibited the fluorescence of the pyrene monomer (lambda(em) = 395 nm) and intramolecular excimer (lambda(em) = 467 nm) emissions. The designed derivative showed the excellent ion sensing ability to Cu2+. The "on-off-off" and "off-on-off" fluorescence responses were demonstrated by the addition of the variable Cu2+ concentration. The utilization of the dual off/on responses could apply to the estimation of the rough Cu2+ concentration.

Seasonal change in the atmospheric concentration of particulate polycyclic aromatic hydrocarbons in Ho Chi Minh City, Vietnam.

We analyzed atmospheric particulate polycyclic aromatic hydrocarbons (PAHs) in Ho Chi Minh City, Vietnam, for 19 months. The average concentrations of total PAHs at dry and rainy seasons were 4.28 +/- 2.83 and 15.71 +/- 8.21 ng m(-3), respectively. The use of motorcycles without catalytic converters, estimated to be main emission sources of PAHs, would be higher during the dry season. PAH concentrations show a negative correlation with sunshine duration (r = -0.51). Furthermore, the ratio of average PAH concentration in the dry season to that in the rainy season shows a positive correlation with photolytic half-life (r = 0.94). Thus, seasonal changes in PAH concentrations are attributable to their photolytic degradation.

C(3)-functionalized cyclotriveratrylene derivative bearing quinolinyl group as a fluorescent probe for Cu(2+).

A new C(3)-functionalized cyclotriveratrylene (CTV) bearing three fluorogenic quinolinyl groups was synthesized and studied as a fluorescent probe. The CTV derivative exhibited a selective response of fluorescence enhancement toward Cu(2+). The fluorescence intensity in CH(3)CN was increased until the [Cu(2+)]/[CTV derivative] mole ratio was 3. Moreover, C(3)-functionalized CTV(2-quinolinemethyl)(3) was applied to a visible fluorescent probe by using a plasticized polymeric membrane. The emission profile was observed by a fluorescence microscope after immersing the membrane in a 1 x 10(-5) M aqueous solution of Cu(2+).

High-throughput assay of nitric oxide metabolites in human plasma without deproteinization by lab-on-a-chip electrophoresis using a zwitterionic additive.

In order to develop a high-throughput assay for nitric oxide metabolites, nitrite (NO2-) and nitrate (NO3-), in biological fluids, we have investigated the simultaneous determination of them using an electrophoretic lab-on-a-chip (microchip capillary electrophoresis, MCE) technique. In this study, in order to establish an MCE assay process without deproteinization, the addition of a zwitterionic additive into the running buffer to reduce the adsorption of protein onto the surface of channel was investigated. Initially, some zwitterionic additives were investigated by making a comparison of relative standard deviations (RSDs) of the migration times for NO2(-) and NO3(-) on capillary electrophoresis. From the results of our comparison of the RSD values, 2% (w/w) N-cyclohexyl-2-aminoethanesulfonic acid (CHES) was selected. As a result of the application of the running buffer with CHES to the MCE process, the complete separation of NO2(-) and NO3(-) in human plasma without deproteinization was achieved within 1 min. Since the RSD values of the positions of the peaks were less than 2.3%, beneficial reduction effects on MCE were suggested. When we used an internal standard method in order to correct the injection volume, the RSDs of the peak heights and areas were less than 10%, and the correlation coefficients of spiked calibration curves ranging from 0 to 350 microM were 0.999 and 0.997 for NO2(-) and NO3(-), respectively. The limits of detection (S/N=3) were 53 microM for NO2(-) and 41 microM for NO3(-). Moreover, the correlation coefficients in excess of 0.99 between the MCE method and a conventional Griess method were achieved for both NO2(-) and NO3(-). Consequently, the possibility of establishing a high-throughput assay process was obtained by utilizing 2% (w/w) CHES to reduce protein adsorption.

On-chip micellar electrokinetic chromatographic separation of phenolic chemicals in waters.

This paper describes on-chip micellar electrokinetic chromatography (MEKC) separation of bisphenol A and 3 kinds of alkylphenols, which have been recently recognized as endocrine disrupting chemicals for fish by the Japanese government, using microchip capillary electrophoresis with UV detection. We successfully obtained high-speed separation of the phenolic chemicals within 15 s as optimizing in microfluidic controls and MEKC separation conditions. We obtained fairly good linearity with correlation coefficient of over 0.98 from 0 to 50 mg/l phenolic chemicals except for 4-nonylphenol, which sample is the mixture of many geometrical isomers (r = 0.86). The values of the relative standard deviation for peak height in 50 mg/l phenolic chemicals were less than 8% except for bisphenol A (11.0%). The limits of detection obtained at a signal-to-noise ratio of 3 were from 5.6 to 20.0 mg/l. To realize on-site monitoring, we described strategy for on-chip MEKC analysis of the phenolic chemicals in waters using a portable analyzer based on microfluidic devices.

Potentiometric performance of silver ion-selective electrodes based on tridentate Schiff base derivatives.

To examine the directivity for improving the silver ion discrimination ability of a Schiff base, three kinds of tridentate ligands were synthesized and compared with the similar quadridentate ligand as the silver ionophore. Among the Schiff base derivatives tested, 3-(2-pyridylethylimino)-2-butanoneoxime, having one oxime and a pyridine substituent, was found to be the best ionophore for a silver-ion electrode. The electrode based on this derivative exhibited good silver-ion selectivity, -log Kpot(Ag+,K+) = 3.8, comparable to that of a quadridentate Schiff base, N,N'-bis(2'-hydroxyimino-1'-phenylpropyleden)-1,3-propanediamine, reported previously, except for a pseudo Nernstian response (35.6 mV decade(-1)) with a wide silver-ion activity change in the activity change from 5.0 x 10(-7) to 7.9 x 10(-2) mol dm(-3).

Synthesis and photochromism of spirobenzopyrans and spirobenzothiapyran derivatives bearing monoazathiacrown ethers and noncyclic analogues in the presence of metal ions.

Spirobenzopyrans bearing monoazathiacrown ethers and noncyclic analogues were synthesized, and their ion-responsive photochromism depending on the dual metal ion interaction with the crown ether and the phenolate anion moieties was examined using alkali and alkaline-earth metal ions, Ag(+), Tl(+), Pb(2+), Hg(2+), and Zn(2+). The prepared spirobenzopyrans showed a selective binding ability to Mg(2+) and Ag(+) with negative and positive photochromism, respectively. Among the metal ions, only Ag(+) facilitated photoisomerization to the corresponding merocyanine form. Depending on the ring size of the monoazathiacrown ether moieties, soft metal ions such as Hg(2+) and Ag(+) showed significant shifts in the UV-vis absorption spectra, while hard metal ions such as Mg(2+), Zn(2+), and Pb(2+) did not afford any meaningful shift. This result reflects that the monoazathiacrown ether and phenolate anion moieties prefer soft and hard metal ions, respectively. Therefore, the Mg(2+) and Ag(+) selectivities are mainly derived from the phenolate anion and monoazathiacrown ether moieties, respectively. On the other hand, a spirobenzothiapyran bearing 3,9-dithia-6-monoazaundecane showed a remarkable selectivity to Ag(+).