Showing papers in "Analytical Sciences in 2010"

Functionalized Nanoparticles and Nanostructured Surfaces for Surface-Assisted Laser Desorption/Ionization Mass Spectrometry

Abstract: Surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF-MS) using nanoparticles (NPs) and nanostructured surfaces as the LDI-assisting nanomaterials is a soft ionization technique that features minimal fragmentation of analytes. As compared to traditional matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) using organic matrices, SALDI-MS affords several advantages, such as the ability to detect small molecules (<500 Da), easy sample preparation, low-noise background, high salt tolerance, and fast data collection without the use of an organic matrix. The performance of SALDI has been further improved recently in terms of the detection sensitivity, detection mass range from the low- to the high-mass region, a soft LDI process, the detection of both polar and nonpolar compounds, the selective detection of analytes from a complex mixture using functionalized NPs, and various applications, including imaging mass spectrometry. This review summarizes recent developments pertaining to various NPs and nanostructured surfaces for SALDI-MS.

Recent nanoarchitectures in metal nanoparticle-modified electrodes for electroanalysis.

Abstract: Increasing attention has been devoted to the use of metal nanoparticles (NPs) for electroanalysis. To make the best use of the electrocatalytic and electron-conducting characteristics of metal NPs, various nanoarchitectures have been developed for modifying metal NPs on electrode surfaces. In this review, at first recent nanoarchitectures with metal NPs for modifying electrodes are summarized together with the results of electrochemical analysis. Then, the progress of a seed-mediated growth method that we developed for modifying electrode surfaces is shown as an example that the nanoarchitectures of metal NPs are possible without using organic linker molecules. This approach should be effective for further functional modifications of the surfaces of metal NPs as well as the electrochemical analysis with lower charge-transfer resistance.

Visualization of Spatial Distribution of γ-Aminobutyric Acid in Eggplant (Solanum melongena) by Matrix-assisted Laser Desorption/Ionization Imaging Mass Spectrometry

Abstract: We applied imaging mass spectrometry (IMS) to determine the spatial distribution of γ-aminobutyric acid (GABA). We found that GABA had a specific localization in seeds. We also visualized various biomolecules as well as GABA with higher spatial resolution than in the previous report. Our work suggests that IMS might be a powerful tool for exploring functional food factors, investigating the specific distribution of nutrients in unused natural resources, and evaluating the quality of functional foods.

Polymer-functionalized gold nanoparticles as versatile sensing materials.

Abstract: In this brief review, gold nanoparticles conjugated with functional polymers are described from the viewpoint of application to sensing materials. The optical properties of gold nanoparticles, the synthesis of polymer-functionalized gold nanoparticles, and their analytical applications are discussed. Polymer-functionalized gold nanoparticles are categorized into two classes: biopolymer-conjugated gold nanoparticles and artificial-polymer conjugated gold nanoparticles. Fluorometric and colorimetric sensing using gold nanoparticles are focused; fluorometric detection enables us to exploit sensitive assays for practical use. Furthermore, chemical amplification using gold nanoparticles is also discussed for the sensitive probing.

Determination of Volatile Organic Compounds for a Systematic Evaluation of Third-Hand Smoking

Abstract: Third-hand smoking was quantitatively evaluated with a polymer-packed sample preparation needle and subsequent gas chromatography-mass spectroscopy analysis. The extraction needle was prepared with polymeric particles as the extraction medium, and successful extraction of typical gaseous volatile organic compounds (VOCs) was accomplished with the extraction needle. For an evaluation of this new cigarette hazard, several types of clothing fabrics were exposed to sidestream smoke, and the smoking-related VOCs evaporated from the fabrics to the environmental air were preconcentrated with the extraction needle. Smoking-related VOCs in smokers' breath were also measured using the extraction needle, and the effect of the breath VOCs on third-hand smoking pollution was evaluated. The results demonstrated that a trace amount of smoking-related VOCs was successfully determined by the proposed method. The adsorption and desorption behaviors of smoking-related VOCs were clearly different for each fabric material, and the time variations of these VOCs concentrations were quantitatively evaluated. The VOCs in the smokers' breath were clearly higher than that of nonsmokers'; however, the results suggested that no significant effect of the smokers' breath on the potential pollution occurred in the typical life space. The method was further applied to the determination of the actual third-hand smoking pollution in an automobile, and a future possibility of the proposed method to the analysis of trace amounts of VOCs in environmental air samples was suggested.

Simultaneous voltammetric determination of enrofloxacin and ciprofloxacin in urine and plasma using multiwall carbon nanotubes modified glassy carbon electrode by least-squares support vector machines.

Abstract: A simple and sensitive method is proposed for the electrochemical determination of enrofloxacin (ENRO) and its primary metabolite ciprofloxacin (CIPRO) at a multiwall carbon nanotubes/glassy carbon electrode (MWCNT/GCE) using a least-squares support vector machine (LS-SVM) and linear sweep voltammetry. Simultaneous determination of ENRO and CIPRO at bare glassy carbon is associated with certain difficulties due to voltammogram overlapping and their low sensitivity. The resolution of the mixture was carried out using LS-SVM as a multivariate calibration method. Under the optimum conditions at pH 7.0, the linear sweep currents increased linearly with ENRO and CIPRO concentrations in ranges of 2.0-780.0 micromol L(-1) (0.7-280.3 microg mL(-1)) and 3.0-1200 micromol L(-1) (1.0-397.7 microg mL(-1)), respectively. The detection limits for ENRO and CIPRO were 0.5 and 0.9 micromol L(-1), respectively. The proposed method was applied to simultaneously determine both compounds in human urine, plasma and in pharmaceutical samples.

Synergistic effect of 18-crown-6 derivatives on chelate extraction of lanthanoids(III) into an ionic liquid with 2-thenoyltrifluoroacetone.

Abstract: The synergistic effect of 18-crown-6 derivatives, such as 18-crown-6 (18C6), cis-dicyclohexano-18-crown-6 (DC18C6) and dibenzo-18-crown-6 (DB18C6), on the extraction of trivalent lanthanoids (Ln3+) into an ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, with 2-thenoyltrifluoroacetone (Htta) was investigated. The extractability of lighter Ln3+ was enhanced by adding 18C6 or DC18C6, whereas no enhancement of the extractability was observed by adding DB18C6. Moreover, the synergistic effect by the crown ether (CE) was increased along with the decrease in the atomic number of Ln. In the synergistic extraction system, Ln3+ was extracted as cationic ternary complexes Ln(tta)2(CE)+ and Ln(tta)(CE)2+, and it was suggested that the formation of the Ln(tta)(CE)2+ complex as an extracted species results in the large synergistic effect. This synergistic effect originated in a size-fitting effect of CE on complexation to Ln3+.

Uphill Transport of Rare-Earth Metals through a Highly Stable Supported Liquid Membrane Based on an Ionic Liquid

Abstract: We have developed a highly stable supported liquid membrane based on ionic liquids (ILs) for the separation of rare-earth metals, employing N,N-dioctyldiglycol amic acid as a mobile carrier. The quantitative transport of Y and Eu through the membrane was successfully attained, and separation from metal impurities, Zn, was efficiently accomplished. A membrane stable enough for long-term operation was constructible from imidazolium-based ILs having a longer alkyl chain, such as octyl or dodecyl groups in an imidazolium cation.

Development of the hard-X-ray angle resolved X-ray photoemission spectrometer for laboratory use

Abstract: This article reports development of a practical laboratory hard X-ray photoelectron spectroscopy (HXPS) system by combining a focused monochromatic Cr Kα X-ray source, a wide angle acceptance objective lens and a high kinetic energy electron analyzer. The Cr Kα source consists of a Cr target, a 15 kV focused electron gun, and a compact bent crystal monochromator. The X-ray spot size is variable from 10 μm (1.25 W) to 200 μm (50 W). A wide acceptance angle objective lens is installed in front of a hemispherical analyzer. The total resolution of 0.53 eV was obtained by Au Fermi-edge measurements. Angle acceptance of ±35° with angle resolution of 0.5° was achieved by measuring Au 3d5/2 peak through a hemicylinder multi-slit on an Au thin strip, in angle resolution mode. As the examples, silicon based multilayer thin films were used for showing the possibilities of deeper (larger) detection depth with the designed system.

Determination of Water Content in Organic Solvents by Naphthalimide Derivative Fluorescent Probe

Abstract: A new fluorescence dye, N-amino-4-(2-hydroxyethylamino)-1,8-naphthalimide (AHN), based on 4-bromo-1,8-naphthalic anhydride was synthesized as a fluorescence probe for determining water content in organic solvents Changing from a non-polar to a polar solvent increases the solvent interaction with excitation spectrum and emission spectrum shifts to longer wavelengths The fluorescence intensity of the probe decreased with the increasing concentration of water In the range of 000 – 400% (v/v), the AHN fluorescence intensity changed as a linear function of water content The detection limits were 0019, 0038, and 0060% for dioxane, acetonitrile and ethanol, respectively

Optimized surface-enhanced Raman scattering (SERS) colloids for the characterization of microorganisms.

Abstract: We report on a comparison of silver colloid preparation methods for the in situ analysis of microorganisms based on surface-enhanced Raman scattering (SERS). Different colloid sols were tested and optimized regarding their suitability as SERS substrates. The silver sols produced by a modified procedure of Leopold and Lendl gave an enhancement factor of the Raman signal in the order 108 for the test molecule, crystal violet. Furthermore, this SERS substrate was successfully applied for the in situ detection and identification of microorganisms immobilized on an immunoassay. The colloid preparation was carried out at room temperature and the colloids were stable for weeks. This silver nanoparticle preparation method for the label-free in situ detection of microorganisms successfully combines SERS with immunoassays. Hence, it has a great potential for the high-throughput detection of biomolecules.

A highly selective colorimetric and "off-on-off" fluorescent probe for fluoride ions.

Abstract: In this paper, a highly selective and sensitive probe for fluoride ions (F(-)), containing a phenylpyridylvinylene derivative reporter and a Si-O bond receptor, was designed and characterized. The reaction mechanism is based on the intramolecular charge transfer (ICT) mechanism. Upon addition of F(-), probe 1 showed a remarkable red-shift (183 nm) in the absorption spectra accompanying with the color changes from colorless to purple, so probe 1 could serve as a "naked-eye" probe for F(-). The absorbance of probe 1 at 545 nm increased linearly with the concentration of F(-) from 20 to 150 µM. The detection limit was calculated to be 0.1 µM. Besides, "off-on-off" fluorescence intensity changes were also observed in the fluorescence spectra. The present results may provide a useful approach for the development of highly selective dual-channel probes for F(-).

Rapid UHPLC method for simultaneous determination of vancomycin, terbinafine, spironolactone, furosemide and their metabolites: application to human plasma and urine.

Abstract: The ultra high performance liquid chromatography (UHPLC)-UV method for the simultaneous determination of furosemide, saluamine (furosemide metabolite), spironolactone, carnenone (spironolactone act ...

Simultaneous voltammetric determination of nitrate and nitrite ions using a copper electrode pretreated by dissolution/redeposition.

Abstract: Nitrate and nitrite ions were found to be successfully electroreduced at an in situ electrochemically pretreated copper electrode in acidic media, and their reduction peaks of a cyclic voltammogram were found at two distinct electrode potentials. Cyclic voltammetric experiments revealed a highly sensitive behavior of the pretreated copper electrode upon the electroreduction of nitrate and nitrite ions, and showed that a simultaneous voltammetric determination of the ions was achievable. Differential pulse voltammetry (DPV) was applied to the simultaneous determination. As a result, the detection limits were 0.26 and 0.17 µmol dm(-3) for nitrate and nitrite ions, respectively. Simultaneous determinations for real samples (river water) were carried out by DPV at the pretreated copper electrode and spectrophotometry (the Griess method). The determination values obtained by both methods were in a good agreement with each other.

Simultaneous Determination of Isoniazid, Pyrazinamide, Rifampicin and Acetylisoniazid in Human Plasma by High-Performance Liquid Chromatography

Abstract: A sensitive and accurate high-performance liquid-chromatography method was developed and validated for the simultaneous determination of pyrazinamide (PZA), isoniazid (INH), rifampicin (RFP) and acetylisoniazid (AcINH) in human plasma. Separation was performed on a Max-RP C(12) column using gradient elution and a flow-rate program. The mobile phase was methanol-acetonitrile-buffer (20 mM of heptanesulfonic acid sodium, pH 2.5) with a ratio of 10:8:82 (v/v/v) at the initial phase. All calibration curves had good linearity (r(2) > 0.99) between the test ranges. The intra- and inter-day precision was less than 8.8% in good accuracy (<15%). The limit of detection with a signal-to-noise (S/N) of 3 was 0.014, 0.009, 0.023 and 0.054 µg mL(-1) for PZA, AcINH, INH and RFP, respectively. The method was selective, sensitive and reliable, and is a good alternative for routine therapeutic drug monitoring of the four compounds during the treatment of tuberculosis patients.

Polydispersity as a parameter for indicating the thermal stability of proteins by dynamic light scattering.

Abstract: A physical parameter for predicting the thermal stability of proteins was provided by a new approach using dynamic light scattering (DLS). The relationship between the melting point measured by differential scanning calorimetry (DSC) and the polydispersity of the hydrodynamic diameter determined by DLS analysis was examined. Calmodulin (CaM) and concanavalin A (ConA) were used as model proteins. The melting point measured by DSC, an indicator for thermal stability, increased and the polydispersity decreased on binding of the proteins to specific ligands, suggesting that the polydispersity could be used an indicator to predict thermal stability. In addition, the increase of thermal stability that resulted from forming a complex could be quantified by polydispersity analysis even when the melting point changed only slightly.

L-Cysteine-capped CdTe Quantum Dots as a Fluorescence Probe for Determination of Cardiolipin

Abstract: This paper described the investigation of surface-modified quantum dots (QDs) as a fluorescence probe for the detection of cardiolipin. A single-step method for preparation of non-toxic and photo-stable cadmium telluride (CdTe) QDs capped by L-cysteine in aqueous solution was developed. The prepared QDs were characterized by high-resolution transmission electron microscopy, X-ray diffraction spectrometry, Fourier transform infrared spectrometry and spectrofluorometry. These functional QDs were used as a fluorescence probe for cardiolipin determination based on the fluorescence quenching. The optimum fluorescence intensity was found to be at pH 7.4 with QDs concentration of 4 × 10−5 mol L−1. The effect of other phospholipids on the intensity of CdTe QDs showed a low interference response. Under optimized conditions, the quenched fluorescence intensity was linear with the concentration of cardiolipin in the range of 1.33 × 10−7 − 10.4 × 10−7 mol L−1 (r = 0.9976) and a detection limit (S/N = 3) of 18.5 nmol L−1. The proposed method was applied to the determination of cardiolipin content of HepG2 cell samples before and after oxidative stress with satisfactory results.

Determination of rare earth elements (REES) in airborne particulate matter (APM) collected in Tokyo, Japan, and a positive anomaly of europium and terbium.

Abstract: The determination of rare earth elements (REEs) in airborne particulate matter (APM) was conducted, and the distribution pattern of atmospheric REEs was evaluated in this study. The APM was collected in the center of Tokyo, Japan, where serious air pollution is always of concern. A cellulose acetate membrane filter was used to collect the APM because Ba and REEs contamination is lower than that in a quartz glass fiber filter. The REEs measurement was conducted by ICP-MS after the digestion of the APM by a microwave acid digestion procedure. The standard reference material (SRM) of NIST 1648 urban particulate matter was used to validate the accuracy of the analytical method. The analytical results for SRM well agreed with those of the reference and reported values. Consequently, the analytical method established in this study was applied to the determination of REEs in APM collected in Tokyo, Japan. The obtained REEs distribution pattern in the APM showed a positive anomaly of Tb and Eu. The La/Sm ratio, which is considered to be as a good indicator of the anthropogenic effect, in size-classified APM showed a high degree of the anthropogenic effect in fine APM with a diameter of <1.1 μm. Emission sources of Tb, Eu and other REEs are discussed.

AFM studies of cellular mechanics during osteogenic differentiation of human amniotic fluid-derived stem cells.

Abstract: Amniotic fluid-derived stem cells (AFSCs) are becoming an important source of cells for regenerative medicine given with apparent advantages of accessibility, renewal capacity and multipotentiality. In this study, the mechanical properties of human amniotic fluid-derived stem cells (hAFSCs), such as the average Young's modulus, were determined by atomic force microscopy (3.97 ± 0.53 kPa for hAFSCs vs. 1.52 ± 0.63 kPa for fully differentiated osteoblasts). These differences in cell elasticity result primarily from differential actin cytoskeleton organization in these two cell types. Furthermore, ultrastructures, nanostructural details on the surface of cell, were visualized by atomic force microscopy (AFM). It was clearly shown that surface of osteoblasts were covered by mineralized particles, and the histogram of particles size showed that most of the particles on the surface of osteoblasts distributed from 200 to 400 nm in diameter, while the diameter of hAFSCs particles ranged from 100 to 200 nm. In contrast, there were some dips on the surface of hAFSCs, and particles were smaller than that of osteoblasts. Additionally, as osteogenic differentiation of hAFSCs progressed, more and more stress fibers were replaced by a thinner actin network which is characteristic of mature osteoblasts. These results can improve our understanding of the mechanical properties of hAFSCs during osteogenic differentiation. AFM can be used as a powerful tool for detecting ultrastructures and mechanical properties.

Visual Detection of Hg2+ with High Selectivity Using Thymine Modified Gold Nanoparticles

Abstract: Here, we describe a colorimetric sensor for detecting Hg(2+) in aqueous media, which is simply constructed by the self-assembly of thymine acetamidoethanethiol (T-SH) on gold nanoparticles (AuNPs). Based on the specific interaction of Hg(2+) with two thymines (T), the T-SH modified AuNPs can be induced to aggregate through the formation of a stable T-Hg-T complex in the presence of Hg(2+), resulting in a color change from red to blue-gray. As low as 0.5 µM of Hg(2+) can be easily monitored by the naked eye using this sensor. Other metal ions, including Zn(2+), Cd(2+), Pb(2+), Ni(2+), Cu(2+), Co(2+), Mn(2+), Ba(2+), Fe(2+), Ca(2+), Mg(2+), Al(3+), and Fe(3+), could not cause any response, even at concentrations 100-fold higher than Hg(2+). The high selectivity, high stability and easy operation enable this sensor suitable for the rapid on-site detection of Hg(2+) pollution.

1H NMR-based metabonomic analysis of metabolic changes in streptozotocin-induced diabetic rats.

Abstract: Diabetes mellitus is a complex metabolic disorder characterized by chronic hyperglycemia, hypoinsulinemia, and ketosis. To access the biochemical process of diabetes, we applied quantitative (1)H NMR-based metabonomics to analyze urine, serum, and liver extracts from streptozotocin-induced diabetic rats. Principle component analysis (PCA) of (1)H NMR spectra disclosed metabolic pattern differences between diabetic and control rats, and identified the related metabolic changes. The PCA scores plot demonstrated that the diabetic group could be distinguished from the control group, indicating that the metabolic characteristics of the two groups were markedly different. Our work reveals the accumulation of triglycerides, fatty acids and acetoacetate in diabetic rats, and may provide an efficient, convenient way for evaluating the pathological state and biochemical process of diabetes mellitus.

Optimization of Removal of Methylene Blue by Platanus Tree Leaves Using Response Surface Methodology

Abstract: Platanus tree leaves were successfully used as a novel sorbent for removing of methylene blue (MB) dye from aqueous solutions. A 23 full factorial design was performed for screening of the main factors. The pH, initial concentration of dye (Cd) and amount of sorbent (m) were considered to be the three main factors at two different levels. It was found that all these factors and their interactions were significant at a certain confidence level (p < 0.05). Doehlert response surface design was applied (13 runs) for a further inspection of the main factors effect, which led to an empirical model. An analysis of the variances (ANOVA) and relevant tests, such as lack-of-fit and residual probability plot, confirmed the validity of the suggested model. A desirability function was used for the simultaneous optimization of both the removal efficiency (R%) and the maximum capacity of the sorbent (q). Plots of the response surface, through visualization of the suggested model, clearly showed the interactions between the main variables and their effects on the response.

Label-free Electrochemical Cocaine Aptasensor Based on a Target-inducing Aptamer Switching Conformation

Abstract: A novel label-free electrochemical nucleic acid aptasensor for the determination of cocaine by the immobilization of thiolated self-assembled DNA sequences on a gold nanoparticles-modified electrode is presented When cocaine was complexed specifically to the aptamer, the configuration of the nucleic acid aptamer switched to a locked structure and the interface of the biosensor changed, resulting in a variation of the corresponding peak current of an electrochemical probe ([Fe(CN)(6)](3-/4-)) Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed to characterize modifications of the electrode surface The peak current was detected by differential pulse voltammetry (DPV) Under the optimized experimental conditions, the presented sensor exhibits a nice specificity towards cocaine The decrease of the peak current response of the aptasensor has a linear relationship with the concentration of cocaine ranging from 10 × 10(-6) to 15 × 10(-4) mol L(-1) with a detection limit of 3 × 10(-7) mol L(-1) at 3σ The proposed aptasensor can be easily regenerated by the denaturalization of aptamer-target complexes in a heated water bath at 80-90°C Besides, this biosensor has a high reproducibility and selectivity, which can be a promising method to detect cocaine in real samples

Rapid determination of nanotoxicity using luminous bacteria.

Abstract: A new luminescence-based toxicity test using luminous bacteria as a reporting agent has been developed to determine EC50 of different nanomaterials, such as gold nanoparticles and carbon nanotubes on living organisms. The whole assay takes only about 15 min and is as sensitive as other standard methods. Due to its technical simplicity, rapidity and sensitivity, this luminescent bacteria test has the potential to be developed as a general test of toxicity for a wide variety of nanomaterials.

Trace Analysis of Polycyclic Aromatic Hydrocarbons Using Gas Chromatography–Mass Spectrometry Based on Nanosecond Multiphoton Ionization

Abstract: Gas chromatography/resonance-enhanced multiphoton ionization/time-of-flight mass spectrometry (GC/REMPI-TOFMS) using an ultraviolet nanosecond laser was employed in the trace analysis of polycyclic aromatic hydrocarbons (PAHs). A standard sample that contained 16 PAHs on the priority list of the Environmental Protection Agency of the United States of America (U.S. EPA) was measured. A sample of river water that had been pretreated by means of solid-phase extraction was analyzed by GC/MS based on electron impact ionization (EI) and REMPI to evaluate the performance of the analytical instrument. The results suggested that REMPI is superior to EI for soft ionization, and suppresses the background signal due to aliphatic hydrocarbons. Thus, GC/REMPI-TOFMS is a more reliable method for the determination of PAHs present in the environment.

Analytical conditions and separation performance of capillary chromatography based on the tube radial distribution of aqueous-organic mixture carrier solvents under laminar-flow conditions.

Abstract: We have developed a capillary chromatography system using an open capillary tube made of fused-silica, polyethylene, or poly(tetrafluoroethylene), and a water–hydrophilic–hydrophobic organic mixture carrier solution. This tube radial distribution chromatography (TRDC) system works under laminar-flow conditions. In this study, the following analytical conditions in the TRDC system using a fused-silica capillary tube and a water–acetonitrile–ethyl acetate mixture carrier solution were for the first time examined: tube temperature, 5 − 25°C; tube inner diameter, 50 − 250 μm; tube effective length, 100 − 200 cm; and flow rate, 0.2 − 1.5 μL min−1. For example, the effects of temperature on the separation performance in the TRDC system were observed with an organic solvent-rich carrier solution; 1-naphthol and 2,6-naphthalenedisulfonic acid in a model mixture were eluted with baseline separation over the temperature range of 5 − 23°C. The resolution, theoretical plate number, and height equivalent to the theoretical plate were calculated from the experimental data obtained by examining the effects of the tube length. A mixture of 1-naphthol, Eosin Y, 1-naphthalenesulfonic acid, 2,6-naphthalenedisulfonic acid, and 1,3,6-naphthalenetrisulfonic acid was subjected to the present TRDC system, and the analytes in the mixture solution were eluted in this order with the organic solvent-rich carrier solution, providing good separation performance on the chromatogram.

Determination of Cr(III) and Cr(VI) at sub-ppb levels in water with solid-phase extraction/metal furnace atomic absorption spectrometry.

Abstract: A simple method using solid-phase extraction combined with metal furnace atomic absorption spectrometry was developed for the determination of Cr(III) and Cr(VI) at sub-ppb levels in water. A 500-ml water sample was adjusted to pH 3 with nitric acid and then passed through an iminodiacetate extraction disk placed on a cation-exchange extraction disk at a flow rate of 20-40 ml min(-1) for concentrating Cr(III). The filtrate was adjusted to pH 10 with aqueous ammonia and then passed through an anion-exchange extraction disk at a flow rate of 2 ml min(-1) for concentrating Cr(VI). The Cr(III) and Cr(VI) collected were eluted with 40 ml of 3 mol l(-1) nitric acid for Cr(III) and 40 ml of 1 g l(-1) diphenylcarbazide solution for Cr(VI). Each eluate was diluted to 50 ml with deionized water and injected into a U-type tungsten board on the metal furnace. The calibration curves of Cr(III) and Cr(VI) showed good linearity in the range of 0.1-0.5 ng. The detection limits corresponding to three times the standard deviation (n = 5) of blank values were 8.1 pg for both Cr(III) and Cr(VI). The analytical value of total Cr (Cr(III) + Cr(VI)) in certified reference material of river water (JSAC 0302-3) was in good agreement with the reference value. The recovery test for 0.50 µg (1.00 µg l(-1)) of Cr(III) and Cr(VI) added to 500 ml of the water samples showed sufficient values (98.1-106%), except for river water sampled downstream due to relatively higher COD(Mn) value. The relative standard deviations (n = 5) were less than 5% for both Cr(III) and Cr(VI).

Statistical analysis of rice samples for compositions of multiple light elements (H, C, N, and O) and their stable isotopes.

Abstract: Stable isotopic compositions and elemental contents of the H, C, N, and O in 163 rice samples were analyzed The samples were taken from three different farming countries; Japan (n = 103), United States of America (n = 30), and Australia (n = 21), in addition of Asian rice samples from Thailand (n = 2), Vietnam (n = 1), and China (n = 6) as comparison They were mostly short grain samples known as "Koshihikari," with several samples of middle and long grains included All samples were grown in the presence of either natural manure or artificial fertilizer The climate of the rice farming environment was diverse, from arid to humid Excluding deltaD data showing large uncertainty, according to the statistical analysis of the principal components based on the stable isotopic compositions such as delta(13)C, delta(15)N, and delta(18)O of rice samples, the Japanese rice samples were clearly distinctive from the Australian and the American rice samples This fact may be explained by the regional differences in isotopic signatures of the climate, utilized nutrition, and/or quality of irrigation water among the farming countries This statistical distinction could be one of the useful tools to extract the rice samples grown in Japan from those grown in the other countries

A Highly Selective Fluorescent Sensor for Cu2+ Based on a Covalently Immobilized Naphthalimide Derivative

Abstract: In this paper, we describe the fabrication and analytical characteristics of fluorescence-based copper ion-sensing glass slides. To construct the sensor, a naphthalimide derivative N-allyl-4-(bis(pyridin-2-ylmethyl)amino)ethylamino-1,8-naphthalimide (1) with a terminal double bond was synthesized and photo-copolymerized with 2-hydroxyethyl methacrylate (HEMA) on a glass surface treated with a silanizing agent. In the presence of Cu2+ at pH 7.24, the resulting optical sensor undergoes fluorescence quenching. Thus, the proposed sensor with visible excitation can behave as a fluorescent sensor for the selective detection of Cu2+. In addition, the sensor exhibits satisfactory selectivity, reproducibility and response time. The sensing membrane possesses a relatively long lifetime of at least 2 months. The linear response range covers a concentration range of Cu2+ from 4.0 × 10−7 to 6.0 × 10−4 mol/L and the detection limit is 2.0 × 10−7 mol/L. The determination of Cu2+ in river water samples shows satisfactory results.

Flow injection determination of iron ions with green tea extracts as a natural chromogenic reagent.

Abstract: A green chemistry system that utilizes natural extract as an alternative reagent for determination of metal ions has been investigated. The extract of green tea, a common beverage, is used for quantification of iron. The green tea extract was prepared in acetate buffer pH 4.8 and could be used without further purification with a simple flow injection (FI) system. The intensity of iron-green tea extract complexes was monitored using a green LED photometer. The use of natural reagent combined with the simple FI-LED photometer set up offers an alternative low cost and rapid system for the determination of metal ions. Detection limit of 0.05 ppm of Fe(III) ion and sampling rate of 180 injections h(-1) were achieved. Application of this system to the analysis of iron in pharmaceutical samples was demonstrated, and the results agreed well with those from the AOAC method.