Development of a digital micromirror spectrometer for analytical atomic spectrometry

A digital micromirror device (DMD) has been incorporated into a novel spectrometer for use in analytical atomic spectrometry. The device can be taken from a commercial computer projector. A protective glass window covering the DMD chip limits the viewable wavelengths to the visible range. The DMD is used to project an image of the light source onto the exit plane of a flat-field spectrograph. A single photomultiplier tube is used for detection. The high switching rate of the micromirrors (15 μs) enables rapid full-spectrum capture, wavelength-modulation, source-modulation, fast narrow-wavelength window scans, and rapid-wavelength "jumping." Calcium, sodium, and potassium have been determined in several standard reference materials (tomato leaves, bovine liver, rice flour, total diet) by flame atomic absorption and emission spectrometry. Absorption sensitivities for each element are near the 0.02 μg/mL level, and detection limits for both absorption and emission are near the 0.01 μg/mL level. Elemental recoveries were within 10% of certified values for most reference materials.     

Trace detection of atmospheric NO2 by laser-induced fluorescence using a GaN diode laser and a diode-pumped YAG laser

We report on the development of a highly sensitive detection system for measuring atmospheric NO(2) by means of a laser-induced fluorescence (LIF) technique at 473 nm using a diode-pumped Nd:YAG laser. A GaN-based laser diode emitting at 410 nm is also used as an alternative fluorescence-excitation source. For laboratory calibrations, standard NO(2) gas is diluted with synthetic air and is introduced into a fluorescence-detection cell. The NO(2) LIF signal is detected by a photomultiplier tube and processed by a photon-counting method. The minimum detectable limits of the NO(2) instrument developed have been estimated to be 0.14 ppbv and 0.39 ppbv (parts per billion, 10(-9), by volume) in 60 s integration time (signal-to-noise ratio of 2) for 473 and 410 nm excitation systems, respectively. Practical performance of the instrument has been demonstrated by the 24 hour continuous measurements of ambient NO(2) in a suburban area.     

ICP－OES法测定镀铬液中多种金属杂质元素

为简便而准确测定镀铬液中金属杂质元素的含量,采用电感耦合等离子体发射光谱法（ICP-OES）对镀铬液中A1,Mn,Fe,Co,Ni,Cu,Zn,Cd,Sb,Pb等杂质元素进行了测定,确定了仪器的最佳工作参数,选择了合适的分析谱线,研究了主量元素cr和共存元素对光谱的干扰情况。结果表明：10种金属元素的检出限为0．15～...     

ICP-AES法测定铝合金中主量元素和杂质元素的方法

用ICP－AES法测定了常见牌号铝合金中B,Cd,Ce,Cr,Cu,Fe,Mg,Mn,Ni,Ti,V,Zn,Zr等主量元素及杂质元素，进行了基体元素与主量元素对分析元素的光谱干扰研究，选择了合适的分析线，用Y作为内标元素，同时测定了分析方法的检出限，该方法准确，快速，简便，能够满足常见牌号铝合金中分析元素的分析。     

Analysis of pure scandium,yttrium, and their oxides using methods of inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry

The analytical possibilities of direct detection of rare earth and non-rare-earth impurities in pure scandium, yttrium, and their oxides using the ICP-AES and ICP-MS methods are investigated. The analytical lines and isotopes of the sought elements that are the most free from folding are selected. The effect of the sought impurities of the matrix elements on the analytical signal is studied. The detection and determination limits for impurities in scandium and yttrium are estimated. The lower limits of determining impurities in scandium, yttrium, and their oxides at the level of n × 10⁴ mass fractions, %, are reached using the ICP-AES method; those at the level of n × 10⁻⁶ mass fractions, %, are reached using the ICP-MS method. The joint application of the ICP-AES and ICP-MS methods for the analysis of standard specimens of yttrium and scandium oxide is implemented. The control of the validity is accomplished by comparing the obtained results with the certified values of standard specimens and by the method of addition.     

Multielemental characterization of several brands of fullerenes and fullerene precursors by instrumental neutron activation analysis

The characterization of the purity of fullerenes is based on the concept of defining the percentage amount of the main component (e.g., C(60), C(70), etc.) versus the minor fractions or microfractions of the homologue species and/or other polycyclic organic compounds. It has also to be considered that fullerene products may be contaminated in some degree by element impurities as well, both from the production processes and from the various precursor materials themselves. We report here for the first time detailed data on trace element impurities in various fullerene precursors as well as in the main C(60) and C(70) fullerene products of different producers, measured by instrumental neutron activation analysis. The concentration distributions of about 35 trace elements have been studied, including the determination of the relevant limits of detection. It could be established that all fullerene materials investigated contain a broad scale of trace elements distributed within a fairly wide concentration range, from ppb (ng/g) up to ppm (μg/g) levels. For some impurity elements, extremely high concentration levels were found, indicating that elemental impurities have to be considered when studying the electrical, magnetic, and other features of the fullerenes.     

氦离子色谱仪在四氟化碳分析中的应用

采用氦离子检测器（PDHID）及以热导检测器（TCD）与火焰离子化检测器（FID）组合的两种不同气相色谱分析方法测定四氟化碳（CF4）中的杂质,结果表明氦离子化检测器（PDHID）灵敏度更高,检测限更低,更适用于电子气体CF4的检测。     

Interferometric measurement of fluorescence excitation spectra

A Michelson interferometer has been adapted as an excitation source for fluorescence spectroscopy. A moving fringe pattern was generated by linear displacement of the movable mirror of the Michelson interferometer coupled to a xenon-arc lamp. This spectrally modulated source was monitored by a reference photomultiplier and used for exciting a Rhodamine B solution. The fluorescence emission at >645 nm was detected by a second photomultiplier. The two interferograms were acquired by a dual-channel digital oscilloscope, and their discrete Fourier transforms and corresponding power spectra were generated in a computer. The power spectrum of the emission signal represented the excitation spectrum, as was confirmed by comparison with the absorption spectrum of Rhodamine B. Thisoptical arrangement is well suited for acquiring fluorescence excitation spectra in the optical microscopy of biological specimens.     

高温气冷堆球形燃料元件中基体石墨杂质含量的研究

研究了高温气冷堆球形燃料元件的基体石墨及所使用的主要原材料中微量及痕量杂质元素的含量，利用等离子发射光谱仪对Ｂ、Ｌｉ、Ｆｅ、Ｔｉ、Ｕ、Ｔｈ、Ｇｄ、Ｅｕ、Ｓｍ、Ｄｙ等十几种重要元素进行了分析，并比较了加工处理过程对于杂质离子含量的影响。研究结果表明，在球形燃料元件制造过程中所使用的原材料及制成的基体石墨均符合球形燃料元件的设计指标。     

集成一次性微流控芯片的便携式荧光检测系统

本文研究了一种新型的生物化学分析系统,该系统包括便携式荧光检测仪和带光纤的微流控芯片．采用基于MEMS技术的微泵将待测物与荧光试剂的混合物导入微流控芯片,采用PMT检测受激发产生的荧光,荧光强度与待测物浓度成一定比例．激发光则通过光纤将光源LED光信号导入微沟道中．随着液体在微沟道中的流动,可连续分析和检测不同的样品．该系统检测1～1000μg／L浓度的荧光素具有0．966的相关系数．基于荧光猝灭原理,该系统还可检测浓度为5ng／μL的硝基化合物．该生化分析系统除具有便携式和一次性微流控芯片优点外,还具有成本低．试剂、样品消耗量少,且分析时间短等优点该系统能实现现场检测,可应用于临床诊断、环境检测及生物战剂检测等领域     

Trace level determination of lead in solid samples by UV laser ablation and laser-enhanced ionization detection

Laser-enhanced ionization was investigated as a detection technique for trace elemental analysis of solid samples by laser ablation. Laser ablation of aluminum samples was performed in an ablation cell, and the ablated material was carried by a flow of gas to a miniature LEI flame where Pb was detected. This decoupling of ablation cell and detector allowed the independent optimization of vaporization and detection processes. We have investigated the different excitation schemes for Pb and uncovered five new LEI-active transitions in the visible range. We have demonstrated that the use of an argon-oxygen/acetylene flame sheathed with argon resulted in the elimination of background interference from the two-photon ionization of nitric oxide. We have shown that the use of helium as a carrier gas results in a higher ablation yield and lower pulse-to-pulse variations in LEI signal and in better analytical figures of merit. We have characterized the performance of the technique in terms of detection limits and dynamic range, and we have obtained a detection limit of 60 ng/g for the determination of Pb in high purity aluminum.     

Finite-element calculations of remote field eddy current interactions with slit defects

Remote field eddy current (RFEC) excitation is a promising approach for detection of the very fine axial cracks typical of stress corrosion cracking (SCC) in pipelines. Interactions between adjacent cracks or slits can enhance responses in some cases. Detailed finite-element modeling was undertaken to establish the behavior and interactions of multiple slits such as those occurring in SCC. Three different field/slit configurations are considered, with anomalous source models used to aid interpretation of the results. The study noted that magnetic perturbations generated by ferromagnetic material tend to be vanishingly small, and that the interactions between multiple cracks give minimal enhancement, indicating that eddy current rather than magnetic field excitation is best for the detection of SCC. With eddy current excitation, field perturbations are generated by even very fine slits, and are larger in non-ferromagnetic material. For nonferromagnetic pipes, the perturbations tend to merge as a circumferential separation between parallel axial cracks decreases, resulting in significant interaction and signal enhancement.     

Parallel detection of intrinsic fluorescence from peptides and proteins for quantification during mass spectrometric analysis

Direct mass spectrometric quantification of peptides and proteins is compromised by the wide variabilities in ionization efficiency which are hallmarks of both the MALDI and ESI ionization techniques. We describe here the implementation of a fluorescence detection system for measurement of the UV-excited intrinsic fluorescence (UV-IF) from peptides and proteins just prior to their exit and electrospray ionization from an ESI capillary. The fluorescence signal provides a quantifiable measure of the amount of protein or peptide present, while direct or tandem mass spectrometric analysis (MS/MS) on the ESI-generated ions provides information on identity. We fabricated an inexpensive, modular fluorescence excitation and detection device utilizing an ultraviolet light-emitting diode for excitation in a ～300 nL fluorescence detection cell integrated into the fused-silica separation column. The fluorescence signal is linear over 3 orders of magnitude with on-column limits of detection in the low femtomole range. Chromatographically separated intact proteins analyzed using UV-IF prior to top-down mass spectrometry demonstrated sensitive detection of proteins as large as 77 kDa.     

Finite-Element Calculations of Remote Field Eddy Current Interactions with Slit Defects

Abstract

Remote field eddy current (RFEC) excitation is a promising approach for detection of the very fine axial cracks typical of stress corrosion cracking (SCC) in pipelines. Interactions between adjacent cracks or slits can enhance responses in some cases. Detailed finite-element modeling was undertaken to establish the behavior and interactions of multiple slits such as those occurring in SCC. Three different field/slit configurations are considered, with anomalous source models used to aid interpretation of the results. The study noted that magnetic perturbations generated by ferromagnetic material tend to be vanishingly small, and that the interactions between multiple cracks give minimal enhancement, indicating that eddy current rather than magnetic field excitation is best for the detection of SCC. With eddy current excitation, field perturbations are generated by even very fine slits, and are larger in non-ferromagnetic material. For non-ferromagnetic pipes, the perturbations tend to merge as a circumferential separation between parallel axial cracks decreases, resulting in significant interaction and signal enhancement.     

原子吸收光谱法测定海洋动物石蚴中的微量元素含量

本文采用火焰原子吸收光谱法测定了石蜐中的锌、铜、铁、锰四种微量元素和镁、钙两种常量元素的含量,精密度为0.26～5.54％,回收率为94.9～104.5％,同时用原子发射法测定了钾元素的含量。     

Method of determination of emission properties of very weakly emitting species ensuring elimination of emission of impurities

This paper describes a new type of spectrofluorimeter, composed of a high-performance liquid chromatography (HPLC) system directly connected to a fluorescence detector and an absorption photodiode array detector, designed for studying the emission of weakly emitting species. Procedures for measurements of emission spectra (ES), emission excitation spectra (EES), and quantum yields of emission (PhiE) for very weakly emitting systems (PhiE>or=10(-7)) have been proposed. The original methodical solution allows verification of whether the emission observed comes solely from the compound studied (and not from its impurities) or from some photochemical or thermal process taking place during measurements. Thanks to the use of this new type of spectrofluorimeter, it is possible to establish with a high probability that the dependence of the shape and position of the ES on the excitation wavelength and the differences between EES and absorptance spectra are due to photophysical and/or photochemical properties of the compound studied and not due to the presence of emitting impurities. An especially interesting application of this method is to study the emission of species whose very weak emission is related to a very short lifetime as well as a low radiative rate constant. It is particularly suitable to the study of the emission properties of flexible molecules that can occur in a few conformers of different absorption and emission properties. The performance of the method is illustrated by the results of the emission studies carried out for Nalpha-acetyl-2-(uracil-5-yl)-L-tryptophan N-ethylamide.     

Fourier transform atomic absorption flame spectrometry with continuum source excitation

The design and performance of a Fourier transform atomic absorption flame spectrometer (FT-AAS) is presented. A 300-W xenon arc continuum source and a Michelson interferometer are used. A signal to noise disadvantage arising from the multiplex feature of FT-AAS is demonstrated by varying the photon flux at the detector without changing the exciting radiation. A grating is used for dispersion of the radiation before the interferometer to reduce the spectral window at the photomultiplier tube. Detection limits for several elements are generally an order of magnitude poorer than those obtained by continuum atomic absorption methods using echelle-grating spectrometers. Line profiles and absorption spectra, within the region of the spectral window selected by the grating, can be obtained with this method. Standard curves for sodium were constructed to extend the linear calibration range, by using absorbances measured at the absorption maximum and 0.022 nm off-line.     

On-line detection of heavy metals and brominated flame retardants in technical polymers with laser-induced breakdown spectrometry

The use of laser-induced breakdown spectrometry (LIBS) for the analysis of heavy metals and brominated flame retardants in end-of-life waste electric and electronic equipment (EOL-WEEE) pieces is investigated. Single- and double-pulse plasma excitation as well as the influence of detection parameters is studied to yield a parameter field with improved sensitivity and limits of detection. A LIBS analyzer was set up as an on-line measuring unit to detect heavy metals and brominated flame retardants in moving EOL-WEEE pieces in an automatic sorting line. An autofocusing unit with an adjustment range of 50 mm was incorporated to permit measurements of objects that pass by a LIBS analyzer with their surfaces at various distances from it. Tests with EOL-WEEE monitor housings on the conveyor belt of a pilot sorting system successfully demonstrated the capability of the LIBS analyzer to quantify the concentration of hazardous elements in real waste EOL-WEEE pieces.     

A large bore-direct injection high efficiency nebulizer for inductively coupled plasma spectrometry

A large bore-direct injection high efficiency nebulizer (IB-DIHEN) is introduced that is less prone to capillary blockage and optimally operates at low nebulizer gas pressures compared with the conventional DIHEN used for inductively coupled plasma (ICP) spectrometries. The aerosol quality is examined using a two-dimensional phase Doppler particle analyzer (2D PDPA), and analytical figures of merits are acquired by ICP mass spectrometry. Compared with the DIHEN, the LB-DIHEN produces larger droplets, but the velocity distributions and mean droplet velocities are narrower and lower, respectively, providing longer residence times for the droplets in the plasma. High RF power (1500 W), low nebulizer gas flow rates (0.25-0.35 L/min), and low solution uptake rates (80-110 microL/min) are required to operate the LB-DIHEN at optimum conditions for ICPMS. Detection limits and sensitivities measured with the LB-DIHEN are superior to those of a conventional nebulizer-spray chamber combination, but precision is inferior. The performance of the LB-DIHEN is further explored in the determination of trace elements in an herbal extract.     

Gating a channel photomultiplier with a fast high-voltage switch: reduction of afterpulse rates in a laser-induced fluorescence instrument for measurement of atmospheric OH radical concentrations

By employing a commercially available high-voltage switch in a time-gating circuit to drive a channel photomultiplier (CPM), the afterpulse rates are significantly reduced in the time window to collect fluorescence >200 ns after the pulsed laser excitation. The CPM, kept deactivated under normal conditions (normally off), is turned on immediately after the passage of the laser pulse by shifting the voltage applied to the photocathode by 150 V to collect the fluorescence. When the detection system is used as part of a laser-induced fluorescence instrument to measure atmospheric OH radicals with the photon-counting method, the background signal is reduced by more than a factor of 10 as compared with our previous case where a conventional dynode-gated photomultiplier tube (PMT) is used, while the sensitivity toward the fluorescence is almost unchanged. A detection limit as low as 2 x 10(5) radicals cm-3 or 0.008 parts per trillion by volume is achieved for OH, with an integration time of 1 min and a signal-to-noise ratio of 2, enabling sensitive detection of the important radical in the atmosphere. This system is a superior choice with higher sensitivity and cost effectiveness as compared with the gated PMITs utilizing a microchannel plate as an electron multiplier, and could also be used effectively in light detection and ranging (lidar) instruments, where a delayed scattering signal would be efficiently discriminated from afterpulses.