Continuum source tungsten coil atomic fluorescence spectrometry

A simple continuum source tungsten coil atomic fluorescence spectrometer is constructed and evaluated. The heart of the system is the atomizer: a low-cost tungsten filament extracted from a 150 W light bulb. The filament is resistively heated with a small, solid-state, constant-current power supply. The atomizer is housed in a glass chamber and purged with a 1 L/min flow of a conventional welding gas mixture: 10% H(2)/Ar. A 25 μL sample aliquot is pipetted onto the tungsten coil, the liquid is dried at low current, and then the atomic vapor is produced by applying a current in the range 3.5-5.5 A. The atomization current does not produce temperatures high enough to excite atomic emission. Radiation from a 300 W xenon lamp is focused through the atomic vapor, exciting atomic fluorescence. Fluorescence signals are collected using a hand-held charge-coupled device (CCD) spectrometer. Simultaneous determination of ten elements (Ag, Bi, Cr, Cu, Ga, In, Mg, Mn, and Tl) results in detection limits in the range 0.3 to 10 ng. The application of higher atomization currents (10 A) leads to straightforward detection of atomic emission signals with no modifications to the instrument.     

Bioimaging of metals and biomolecules in mouse heart by laser ablation inductively coupled plasma mass spectrometry and secondary ion mass spectrometry

Bioimaging mass spectrometric techniques allow direct mapping of metal and biomolecule distributions with high spatial resolution in biological tissue. In this study laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) was used for imaging of transition metals (Fe, Cu, Zn, Mn, and Ti), alkali and alkaline-earth metals (Na, K, Mg, and Ca, respectively), and selected nonmetals (such as C, P, and S) in native cryosections of mouse heart. The metal and nonmetal images clearly illustrated the shape and the anatomy of the samples. Zinc and copper were inhomogeneously distributed with average concentrations of 26 and 11 μg g(-1), respectively. Titanium and manganese were detected at concentrations reaching 1 and 2 μg g(-1), respectively. The highest regional metal concentration of 360 μg g(-1)was observed for iron in blood present in the lumen of the aorta. Secondary ion mass spectrometry (SIMS) as an elemental and biomolecular mass spectrometric technique was employed for imaging of Na, K, and selected biomolecules (e.g., phosphocholine, choline, cholesterol) in adjacent sections. Here, two different bioimaging techniques, LA-ICPMS and SIMS, were combined for the first time, yielding novel information on both elemental and biomolecular distributions.     

Highly sensitive elemental analysis for Cd and Pb by liquid electrode plasma atomic emission spectrometry with quartz glass chip and sample flow

This paper describes the development of a highly sensitive liquid-electrode plasma atomic emission spectrometry (LEP-AES) by combination of quartz glass chip and sample flow system. LEP-AES is an ultracompact elemental analysis method, in which the electroconductive sample solution is put into a microfluidic channel whose center is made narrower (～100 μm in width). When high voltage pulses (1500 V) are applied at both ends of the channel, the sample evaporates locally at the narrow part and generates plasma. By the emission from the plasma, elemental concentration is analyzed. In this paper, the limits of detection (LODs) were investigated in various conditions of accumulation time, material of the chip, and the sample flow. It was found that the long accumulation using the quartz chip with sample flow was effective to improve LOD. Authors suggested that this was because bubbles remaining after each plasma pulse were removed from the narrow channel by sample flow, resulting in highly reproducible plasma generation, to enable a high accumulation effect. Finally, LODs were calculated from a calibration curve, to be 0.52 μg/L for Cd and 19.0 μg/L for Pb at optimized condition. Sub-ppb level LOD was achieved for Cd.     

Liquid sampling-atmospheric pressure glow discharge ionization source for elemental mass spectrometry

A new, low power ionization source for elemental MS analysis of aqueous solutions is described. The liquid sampling-atmospheric pressure glow discharge (LS-APGD) operates by a process wherein the surface of the liquid emanating from a 75 μm i.d. glass capillary acts as the cathode of the direct current glow discharge. Analyte-containing solutions at a flow rate of 100 μL min(-1) are vaporized by the passage of current, yielding gas phase solutes that are subsequently ionized in the <5 W (maximum of 60 mA and 500 V), ~1 mm(3) volume, plasma. The LS-APGD is mounted in place of the normal electrospray ionization source of a Thermo Scientific Exactive Orbitrap mass spectrometer system without any other modifications. Basic operating characteristics are described, including the role of discharge power on mass spectral composition, the ability to obtain ultrahigh resolution elemental isotopic patterns, and demonstration of potential limits of detection based on the injection of aliquots of multielement standards (S/N > 1000 for 5 ng mL(-1) Cs). While much optimization remains, it is believed that the LS-APGD ion source may present a practical alternative to high-powered (>1 kW) plasma sources typically employed in elemental mass spectrometry, particularly for those cases where costs, operational overhead, simplicity, or integrated elemental/molecular analysis considerations are important.     

氧弹燃烧-离子色谱法测定螺旋藻中碘

建立氧弹燃烧-离子色谱法测定螺旋藻中碘含量方法。方法选用Metrosep A Supp 4色谱柱,1.8mmol/L Na2CO3+1.7mmol/L NaHCO3淋洗液,流速1mL/min,电导检测器。样品氧弹燃烧法处理,然后用(0.714g NaHCO3+0.954g Na2CO3)/L吸收液吸收,定容后过滤待测。用于螺旋藻样品分析,回收率为102%。本法快速、简便、灵敏。样品测定结果令人满意。     

KNN/BNT composite lead-free films for high-frequency ultrasonic transducer applications

Lead-free K(0.5)Na(0.5)NbO(3)/Bi(0.5)Na(0.5)TiO(3) (KNN/ BNT) films have been fabricated by a composite sol-gel technique. Crystalline KNN fine powder was dispersed in the BNT precursor solution to form a composite slurry which was then spin-coated onto a platinum-buffered Si substrate. Repeated layering and vacuum infiltration were applied to produce 5-μm-thick dense composite film. By optimizing the sintering temperature, the films exhibited good dielectric and ferroelectric properties comparable to PZT films. A 193-MHz high-frequency ultrasonic transducer fabricated from this composite film showed a -6-dB bandwidth of approximately 34%. A tungsten wire phantom was imaged to demonstrate the capability of the transducer.     

Synthesis of molecularly imprinted polymer as a sorbent for solid phase extraction of citalopram from human serum and urine

This paper describes a new method for the determination of citalopram in biological fluids using molecularly imprinted solid-phase extraction as the sample cleanup technique combined with high performance liquid chromatography. The molecularly imprinted polymers were prepared using methacrylic acid as functional monomer, ethylene glycol dimethacrylate as crosslinker, chloroform as porogen and citalopram hydrobromide as the template molecule. The novel imprinted polymer was used as a solid-phase extraction sorbent for the extraction of citalopram from human serum and urine. Effective parameters on citalopram retention were studied. The optimal conditions for molecularly imprinted solid-phase extraction consisted of conditioning with 1 mL methanol and 1 mL of deionized water at neutral pH, loading of citalopram sample (50 μg L(-1)) at pH 9.0, washing using 1 mL acetone and elution with 3 × 1 mL of 10 % (v/v) acetic acid in methanol. The MIP selectivity was evaluated by checking several substances with similar molecular structures to that of citalopram. Results from the HPLC analyses showed that the calibration curve of citalopram using MIP from human serum and urine is linear in the ranges of 1-100 and 2-120 μg L(-1) with good precisions (2.5 and 1.5 % for 10.0 μg L(-1)), and recoveries (between 82-86 and 83-85 %), respectively.     

Tungsten and other heavy metal contamination in aquatic environments receiving wastewater from semiconductor manufacturing

Through analyses of water and sediments, we investigate tungsten and 14 other heavy metals in a stream receiving treated effluents from a semiconductor manufacturer-clustered science park in Taiwan. Treated effluents account for ～ 50% of total annual river discharge and <1% of total sediment discharge. Dissolved tungsten concentrations in the effluents abnormally reach 400 μg/L, as compared to the world river average concentration of <0.1 μg/L. Particulate tungsten concentrations are up to 300 μg/g in suspended and deposited sediments, and the corresponding enrichment factors are three orders of magnitude higher than average crust composition. Surprisingly, the estimated amount of tungsten exported to the adjacent ocean is 23.5 t/yr, which can approximate the amount from the Yangtze River should it be unpolluted. This study highlights the urgency of investigating the biological effect of such contamination.     

Determination of boron by flow injection analysis using a conductivity detector

A flow injection method for the determination of boron using a conductivity detector has been described. Boric acid injected into the flow system reacts with mannitol (0.3 M) in the mobile phase and an equivalent amount of H(+) is liberated in the stream. The increase in the conductance of the mobile phase due to the liberated H(+) has been equated to the boron concentration in the sample. A linear calibration for light- and heavy-water samples containing 0-20 μg/mL boron was obtained. Boron concentrations in the samples of light and heavy water and lithium pentaborate solution have been measured. The interferences due to various ions such as Na(+), Li(+), Cu(2+), Ni(2+), Co(2+), Fe(3+), Al(3+), SO(4)(2-), NO(3)(-), F(-), and Cl(-) could be eliminated by adopting a two-step sample pretreatment procedure. In the first step, all the anions were converted to Cl(-) by treating the sample solution with a strong anion-exchange resin. In the second step, the solution obtained from the first step was passed through a silver-guard cartridge to remove interfering cations and Cl(-). The relative standard deviation was ±0.25% for the determination of 1 μg of boron in light water, and the limit of detection was 0.01 μg present in an injection volume of 100 μL. The corresponding values for heavy water were ±0.38% and 0.1 μg, respectively.     

掺ZBS玻璃低温烧结ZnNb2O6微波介质陶瓷的研究

研究了ZnO-B2 O3-SiO2(ZBS)玻璃料对ZnNb2O6微波介质陶瓷烧结特性和介电性能的影响.结果表明,ZBS玻璃料形成的液相加速了颗粒间的传质,促进了烧结,能使ZnNb2O6陶瓷的烧结温度有效地降低至950℃.随着ZBS含量的增加,样品中出现了第二相,且气孔被包裹在晶粒内部难以逃脱出来,导致样品的缺陷和损耗增加,从而降低介电性能.掺杂1%ZBS的ZnNb2O6陶瓷在950℃保温4h,能获得优异的综合介电性能:ε=23.56、Q·f=18482GHz、τf=-28.8×10￣6/℃.     

Determination of Pentachlorophenol and Its Oil Solvent in Wood Pole Samples by SFE and GC with Postcolumn Flow Splitting for Simultaneous Detection of the Species

An alternative approach is described for the measurement of pentachlorophenol (PCP) and its oil solvent in wood samples by supercritical fluid extraction (SFE) and gas chromatography (GC). The determination is achieved over a single chromatographic run using postcolumn flow splitting for simultaneous ECD/FID detection of the SFE extracted species. First, PCP and oil components are quantitatively extracted from a 0.3-g wood sample using 10% MeOH/CO(2) supercritical fluid at 0.65 g/mL and 120 °C. An aliquot of the SFE solution is then mixed with 10 mL of a buffered aqueous phase at pH 9.4. After PCP is acetylated by the addition of 500 μL of acetic anhydride, it is followed by its extraction with 2.00 mL of hexane along with oil. Then, 0.5 μL of supernatant organic phase is injected into the GC for a selective and simultaneous determination of the species. The method has a linear response over 3 orders of magnitude for both species with a linear regression correlation coefficient higher than 0.98 (95% confidence limit) and an absolute detection limit of 60 ng of PCP and 80 μg of oil per 0.1-g wood sample. The precision (relative standard deviation) is 4% for PCP and 1% for oil as established for a typical average concentration sample. The accuracy of the SFE GC-ECD/FID combined technique for PCP and oil was assessed by analyzing wood samples collected from newly and in-service PCP/oil-impregnated red pine poles.     

Visualization of dynamic fiber-matrix interfacial shear debonding

To visualize the debonding event in real time for the study of dynamic crack initiation and propagation at the fiber–matrix interface, a modified tension Kolsky bar was integrated with a high-speed synchrotron X-ray phase-contrast imaging setup. In the gage section, the pull-out configuration was utilized to understand the behavior of interfacial debonding between SC-15 epoxy matrix and S-2 glass fiber, tungsten wire, steel wire, and carbon fiber composite Z-pin at pull-out velocities of 2.5 and 5.0 m s^?1. The load history and images of the debonding progression were simultaneously recorded. Both S-2 glass fiber and Z-pin experienced catastrophic interfacial debonding whereas tungsten and steel wire experienced both catastrophic debonding and stick–slip behavior. Even though S-2 glass fiber and Z-pin samples exhibited a slight increase and tungsten and steel wire samples exhibited a slight decrease in average peak force and average interfacial shear stress as the pull-out velocities were increased, no statistical difference was found for most properties when the velocity was increased. Furthermore, the debonding behavior for each fiber material is similar with increasing pull-out velocity. Thus, the debonding mechanism, peak force, and interfacial shear stress were rate insensitive as the pull-out velocity doubled from 2.5 to 5.0 m s^?1. Scanning electron microscope imaging of recovered epoxy beads revealed a snap-back behavior around the meniscus region of the bead for S-2 glass, tungsten, and steel fiber materials at 5.0 m s^?1 whereas those at 2.5 m s^?1 exhibited no snap-back behavior.     

Optimization of the Simultaneous Determination of Cr(III) and Cr(VI) by Ion Chromatography with Chemiluminescence Detection

An optimized method for the simultaneous determination of Cr(III) and Cr(VI) in aqueous solutions using ion chromatography with chemiluminescence detection is described. Excellent resolution of the two chromium species was obtained using a single mixed-bed ion-exchange column with continuous elution. After postcolumn reduction of Cr(VI) to Cr(III), the light emitted during the Cr(III)-catalyzed oxidation of luminol with hydrogen peroxide was measured. Parameters affecting the postcolumn reactions such as reductant concentration, reductant mixing, point of luminol introduction, and luminol flow rate were optimized. The calibration curves in the range tested (0.01-50 μg L(-)(1)) were linear, and detection limits of 0.002 μg L(-)(1) for both Cr(III) and Cr(VI) were obtained. The results of the analyses of the water reference materials LGC CRM6010 and NIST SRM1643d with certified chromium values of 49 ± 4 and 18.53 ± 0.20 μg L(-)(1) and found to contain only Cr(III) were 49.2 ± 1.8 and 19.0 ± 1.5 μg L(-)(1), respectively. Values of 10.6 ± 0.5 and 10.1 ± 0.5 μg L(-)(1) were obtained when a simulated water sample containing 10 μg L(-)(1) Cr(III) and Cr(VI) was analyzed.     

Portable laser ablation sampling device for elemental fingerprinting of objects outside the laboratory with laser ablation inductively coupled plasma mass spectrometry

Laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) is a powerful method for elemental fingerprinting of solid samples in a quasi-nondestructive manner. In order to extend the field of application to objects outside the laboratory, a portable laser ablation sampling device was assembled using a diode pumped solid state laser and fiber-optics. The ablated materials were sampled on membrane filters and subsequently quantified by means of LA-ICPMS. The analytical performance of this approach was investigated for glass and gold reference materials. Accuracies of better than 20% were reached for most elements and typical limits of detection were found to be in the range of 0.01-1 μg/g. In summary, this approach combines spatially resolved sampling with the detection power of ICPMS and enables elemental fingerprinting of objects which cannot be transferred to the laboratory, e.g., archeological artifacts in museums.     

Preconcentration and separation of copper, nickel and zinc in aqueous samples by flame atomic absorption spectrometry after column solid-phase extraction onto MWCNTs impregnated with D2EHPA-TOPO mixture

A solid phase extraction method has been developed for the determination of copper, nickel and zinc ions in natural water samples. This method is based on the adsorption of copper, nickel and zinc on multiwalled carbon nanotubes (MWCNTs) impregnated with di-(2-ethyl hexyl phosphoric acid) (D2EHPA) and tri-n-octyl phosphine oxide (TOPO). The influence of parameters such as pH of the aqueous solution, amount of adsorbent, flow rates of the sample and eluent, matrix effects and D2EHPA-TOPO concentration have been investigated. Desorption studies have been carried out with 2 mol L(-1) HNO(3). The copper, nickel and zinc concentrations were determined by flame atomic absorption spectrometry. The results indicated that the maximum adsorption of copper, nickel and zinc is at pH 5.0 with 500 mg of MWCNTs. The detection limits by three sigma were 50 μg L(-1) for copper, 40 μg L(-1) for nickel and 60 μg L(-1) zinc. The highest enrichment factors were found to be 25. The adsorption capacity of MWCNTs-D2EHPA-TOPO was found to be 4.90 mg g(-1) for copper, 4.78 mg g(-1) for nickel and 4.82 mg g(-1) for zinc. The developed method was applied for the determination of copper, nickel and zinc in electroplating wastewater and real water sample with satisfactory results (R.S.D.'s <10%).     

Synthesis, characterization and analytical application of hybrid; acrylamide zirconium (IV) arsenate a cation exchanger, effect of dielectric constant on distribution coefficient of metal ions

A new hybrid inorganic-organic cation exchanger acrylamide zirconium (IV) arsenate has been synthesized, characterized and its analytical application explored. The effect of experimental parameters such as mixing ratio of reagents, temperature, and pH on the properties of material has been studied. FTIR, TGA, X-ray, UV-vis spectrophotometry, SEM and elemental analysis were used to determine the physiochemical properties of this hybrid ion exchanger. The material behaves as a monofunctional acid with ion-exchange capacity of 1.65 meq/g for Na(+) ions. The chemical stability data reveals that the exchanger is quite stable in mineral acids, bases and fairly stable in organic solvents, while as thermal analysis shows that the material retain 84% of its ion-exchange capacity up to 600 degrees C. Adsorption behavior of metal ions in solvents with increasing dielectric constant has also been explored. The sorption studies reveal that the material is selective for Pb(2+) ions. The analytical utility of the material has been explored by achieving some binary separations of metal ions on its column. Pb(2+) has been selectively removed from synthetic mixtures containing Mg(2+), Ca(2+), Sr(2+), Zn(2+) and Cu(2+), Al(3+), Ni(2+), Fe(3+). In order to demonstrate practical utility of the material quantitative separation of the Cu(2+) and Zn(2+) in brass sample has been achieved on its columns.     

Electrochemical determination of trihalomethanes in water by means of stripping analysis

A protocol has been developed and evaluated for the determination of trihalomethanes (THMs) at the submicromolar concentration level in water. This method is based on a three-step stripping analysis that utilizes a single electrochemical cell and that entails (a) direct electrochemical reduction of a trihalomethane at a silver cathode to form halide ions in an aqueous sample containing tetraethylammonium benzoate, (b) capture of the released halide ions as a silver halide film on the surface of a silver gauze anode, and (c) cathodic reduction and quantitation of the silver halide film by means of differential pulse voltammetry. Using this procedure, we have determined THMs individually; bromoform and chloroform have been successfully quantitated in 30 min and with a detection limit of 3.0 μg L(-1) (12 nM) and 6.0 μg L(-1) (50 nM), respectively. In addition, we have employed our methodology to determine the total trihalomethane (TTHM) content in a prepared water sample at a level commensurate with the maximum allowable annual average of 80 μg L(-1) mandated by the United States Environmental Protection Agency. We have compared our TTHM results to those obtained by an independent testing laboratory.     

Impact of beta-cypermethrin on soil microbial community associated with its bioavailability: a combined study by isothermal microcalorimetry and enzyme assay techniques

In this study, an isothermal microcalorimetric technique has been used to show that beta-cypermethrin (CYP) had no significant effect (p > 0.05) on soil microbial activity at 80 μg g(-1) soil. Our soil enzyme data indicated that beta-CYP ranging 10-80 μg g(-1) soil had no significant effect (p > 0.05) on soil enzyme activities such as β-glucosidase, urease, acid-phosphatase, and dehydrogenase. Therefore, our results infer that beta-CYP would not pose severe toxicity to soil microbial community, but its toxic level may vary greatly with environment that associates with its increase in bioavailability: the level in soil (at μg g(-1)) < the level in sediment (varying from μg g(-1) to μg L(-1)) 0.05). These results suggest that the heavy application of beta-CYP may not cause damage to soil microbial community which is very different from its high toxicity to the aquatic organism.     

微量Si在W－7Ni－3Fe重合金中的行为

研究了掺到原料Ｗ粉中微量Ｓｉ（４００ｐｐｍ）在Ｗ－７Ｎｉ－３Ｆｅ重合金中的分布及在液相烧结过程中的行为．结果表明，Ｓｉ主要以固溶形式分布在Ｗ晶粒中．Ｘ射线光电子能谱（ＸＰＳ）分析发现，在掺杂Ｓｉ的Ｗ－Ｗ及Ｗ－基体相界面富集ＳｉＯ２和Ｎａ２ＳｉＯ３在未掺杂试样的断口表面发现了较弱的ＷＯ２的ＸＰＳ谱，而在掺杂合金中未发现ＷＯ２．     

Sample preparation using a miniaturized supported liquid membrane device connected on-line to packed capillary liquid chromatography

A miniaturized supported liquid membrane device has been developed for sample preparation and connected on-line to a packed capillary liquid chromatograph. The device consists of hydrophobic polypropylene hollow fiber, inserted and fastened in a cylindrical channel in a Kel-F piece. The pores of the fiber are filled with an organic solvent, in this study 6-undecanone, thus forming a liquid membrane. The sample is pumped on the outside of the hollow fiber (donor), and the analytes are selectively enriched and trapped in the fiber lumen (acceptor). With this approach, the volume of the acceptor solution can be kept as low as 1-2 μL. This stagnant acceptor solution is then transferred through capillaries attached to the fiber ends to the LC system. The system was tested with a secondary amine (bambuterol), as a model substance in aqueous standard solutions as well as in plasma. The best extraction efficiency in aqueous solution, with an acceptor volume of 1.9 μL, was 32.5% at a donor flow rate of 2.5 μL/min. At flow rates above 20 μL/min, the concentration enrichment per time unit was approximately constant, at 0.9 times/min, i.e., 9 times enrichment in about 10 min. The overall repeatability (RSD) for spiked plasma samples was ～4% (n = 12). Linear calibration curves of peak area versus bambuterol concentration were obtained for both aqueous standard solutions and spiked plasma samples. The detection limit for bambuterol in plasma, after 10 min of extraction at a flow rate of 24 μL/min, was 80 nM.