Precise Measurement of Isotope Ratios with a Double-Focusing Magnetic Sector ICP Mass Spectrometer

The potential of a commercially available double-focusing magnetic sector ICP mass spectrometer (Element, Finnigan MAT, Bremen, Germany) for precise isotope ratio measurement at the low-resolution setting (R = 300) was evaluated. Optimization of scanning conditions led to a relative standard deviation for a set of 10 consecutive 2 min measurements of ～0.1% ((206)Pb(+)/(207)Pb(+)) at signal intensities of ～200?000 counts/s (peak height). This compares favorably with the best values ever reported for quadrupole ICPMS and barely exceeds the theoretical value (counting statistics). Increasing the signal intensity to values ≥500?000 counts/s (peak height) resulted in a further reduction of the RSDs obtained (for both (25)Mg(+)/(26)Mg(+) and (206)Pb(+)/(207)Pb(+)) to typically 0.04%. These figures are remarkably better than those reported for commercially available quadrupole ICPMS systems. This improvement significantly reduces the difference between isotope ratio precision of ICPMS on one hand and those of thermal ionization mass spectrometry and plasma source multiple collector mass spectrometry on the other.     

Aerosol MALDI with a Reflectron Time-of-Flight Mass Spectrometer

Aerosol matrix-assisted laser desorption/ionization (MALDI) has been combined with a reflectron time-of-flight mass spectrometer for improved mass resolution. A methanol solution of matrix and analyte was sprayed directly into a reflectron time-of-flight mass spectrometer, and the aerosol particles were irradiated and ionized with a frequency-tripled Nd:YAG laser at 355 nm. Mass resolution of over 300 was observed for the peptides bradykinin, angiotensin II, and gramicidin D and for vitamin B(12). This represents a resolution enhancement of approximately 10-fold over that previously reported for aerosol MALDI with a linear time-of-flight instrument.     

污染对四极质谱计性能的影响

本文就四级质谱计污染对性能的影响进行了详细研究,分析了污染产生的过程,给出了污染前后离子源特性的变化;并对四极杆污染后离子工作点的变化进行分析计算,由此得出污染子注传输性能的影响,最后提出了克服和减污染影响的方法。     

液相色谱-质谱联用仪的性能检测

液相色谱-质谱联用仪是目前最重要的定性、定量分析仪器之一,在食品安全、生物、医药、化工等领域中均得到了广泛的应用,在组合化学、蛋白质组学和代谢化学的研究工作中,液质已经成为最重要的研究方法之一,但至今我省还没有形成统一的检测规范。本文根据仪器的实际检测要求,参考相关仪器的技术标准,制定了该仪器的校准规范。并对电喷雾离子源和大气压化学离子源下三种质量分析器进行检测,通过指标评价最终确定了此种方法的可行性。     

飞行时间质谱仪技术性能研究

阐述了飞行时间质谱仪的构成、基本原理、性能特点,提出了评价飞行时间质谱仪性能的主要技术要求。     

Laser Time-of-Flight Mass Spectrometry of PAH-Picrate Complexes

The laser desorption/laser ionization time-of-flight (L2ToF), mass spectra of anthracene and the anthracene-picric acid charge transfer (C-T) complex have been compared at a desorption and ionization wavelength of 266 nm. Laser desorption/ionization spectra of anthracene were obtained at low temperatures (-30 °C) to minimize the interference from gas phase ionization. Positive ion mass spectra of the picrate C-T complex at room temperature comprise the parent ion of anthracene and were devoid of signals associated with the picric acid component. The L2ToF analyses of a mixture of volatile and involatile EPA priority PAHs in picric acid show that low molecular weight PAHs form involatile charge transfer complexes. The present method reduces the possibility of volatile PAH loss during mass spectrometric analyses in vacuo.     

Use of Thermal Ionization Mass Spectrometry for Measuring the Oxygen Isotope Ratio in Uranium Oxides1,2

A method was developed for precise determination of oxygen isotope ratios in uranium oxides. Thermal ionisation mass spectrometry (TIMS) was used for direct measurements of n(U^{1 8}O⁺)/n(U^{1 6}O⁺) using the molecular species UO⁺. Suitable sample handling and filament preparation techniques were developed in order to obtain reproducible results and avoid oxygen contamination. The actual measurements were performed using the total evaporation method. By this technique the achieved precision for n(U^{1 8}O⁺)/n(U^{1 6}O⁺) measurements was in the range of 0.04%. The peak jump techniques was also used for measurements, and the results of both techniques are discussed. The TIMS measurement are verified by comparative measurements using secondary ion mass spectrometry (SIMS).     

On-Line Emission Analysis of Polycyclic Aromatic Hydrocarbons down to pptv Concentration Levels in the Flue Gas of an Incineration Pilot Plant with a Mobile Resonance-Enhanced Multiphoton Ionization Time-of-Flight Mass Spectrometer

A newly developed, mobile laser mass spectrometer (resonance-enhanced multiphoton ionization - time-of-flight mass spectrometer, REMPI-TOFMS) was applied to on-line measurements at a waste incineration pilot plant. REMPI-TOFMS combines the optical selectivity of resonance-enhanced multiphoton ionization with a time-of-flight mass analysis to give a two-dimensional analytical method. Special care was taken to build up a sampling and inlet system suitable for on-line measurements of large, semivolatile polycyclic aromatic hydrocarbons (PAHs). An effusive molecular beam inlet in combination with a fixed frequency UV laser (Nd:YAG at 266 nm or KrF excimer at 248 nm) was used. Under these conditions, many different PAHs can be ionized selectively from the complex flue gas matrix. For example, the achieved detection limit for naphthalene is in the 10 parts-per-trillion by volume (pptv) concentration range. Calibration was performed by using external concentration standards supplied in low ppbv concentrations. The instrumentation is sufficiently robust to be operated under industrial conditions at incineration plants, for instance. The REMPI mass spectra can be acquired at 5-50 Hz. Time profiles of the concentrations of different PAHs in the flue gas were monitored with a time resolution of 200 ms. Significant variations in the concentration profile of several PAHs up to mass 276 amu (e.g., benzo[ghi]perylene) and methylated PAHs have been observed while combustion parameters were changing. In summary, it was demonstrated that laser mass spectrometry (REMPI-TOFMS) enables a real-time on-line trace analysis of combustion flue gases or industrial process gases.     

核壳质量比对石蜡-聚脲相变微胶囊性能的影响

以质量比为3∶7的固体石蜡与液体石蜡均匀混合得到复合石蜡,甲苯-2,4-二异氰酸酯(TDI)单体和乙二胺(EDA)在乳化剂辛基酚聚氧乙烯醚的乳化作用下,通过界面聚合包覆在芯材复合石蜡的表面形成石蜡-聚脲相变微胶囊,对比差热曲线和加热-冷却曲线表征芯材复合石蜡的蓄热性能,探讨EDA与TDI质量比对聚脲囊壁产量的影响,以及核壳质量比对石蜡-聚脲相变微胶囊粒径、包覆效率以及蓄热性能的影响。结果表明:加热-冷却曲线与差示扫描量热曲线显示复合石蜡的熔点接近;聚脲囊壁的产量随着水合EDA与TDI质量比的增大近似线性增大,质量比达到0.5∶1.0后,聚脲囊壁的产量不再增大;核壳质量比为2.0∶1.0时制得石蜡-聚脲相变微胶囊的熔点为28.1℃,相变焓为58.4 k J/kg,包覆效率为87.5%,粒径约为4.32μm,粒径分布均匀。     

分压强质谱计校准装置的研制

分压强质谱计校准装置用于质谱计的校准。本文介绍了分压强质谱计校准装置的结构、工作原理及分压强测量方法,并给出了分压强测量的不确定度分析。     

激光电离反射式串级飞行时间质谱仪的离子轨迹模拟和性能研究

通过离子轨迹模拟对用二阶空间聚焦条件设计的激光电离反射式串级飞行时间质谱仪的性能进行了研究 ,其中包括离子源在不同离子注入条件下的空间聚焦性能 ,有栅网和无栅网反射器的性能 ,栅丝效应 ,检测器平面位置以及质量门、光解点和后加速电极对性能的影响等。模拟结果对实际仪器的调试运行也提供了重要的参考依据     

Combined Ion Mobility/Time-of-Flight Mass Spectrometry Study of Electrospray-Generated Ions

A commercially available ion mobility spectrometer was interfaced to a custom-built linear time-of-flight (TOF) mass spectrometer for the purpose of examining electrospray-generated plumes. Ionic species that were separated in the ion mobility spectrometer could be selectively determined with the TOF mass spectrometer. Tetraalkylammonium salts, a peptide, and proteins were examined. Their ion mobility spectra typically comprised a few peaks; some of these mobility-resolved species produced characteristic electrospray ions, while others of lower relative mobility did not. The TOF mass spectra of cytochrome c, injected from the ion mobility spectrometer at an indicated temperature of 90 °C or lower, showed signs that were characteristic of protein-solvent clustering.     

ICP发射光谱仪测六种元素检出限测量结果不确定度分析

本文介绍了ICP发射光谱仪测六种元素检出限测量结果不确定度分析.     

质谱仪的自动供样系统设计

本文介绍以AT89C52单片机为主控核心,采用电机驱动方式切换被测样品,有供样方式切换、测量时间设置、显示样品号等功能,广泛适用于各种固相、液相分析仪的自动供样。     

氦质谱背压检漏方法研究

阐述了氦质谱背压检漏的特点及目前存在的问题,在此基础上提出了改进建议。深入探讨了预充氦背压法测得的测量漏率与等效标准漏率的关系,指出预充氦背压法可用于检测压氦背压法检测不到的小漏孔,给出了等效标准漏率对测量漏率具有的双值均在分子流范围时的鉴别方法。     

用Bessel-Box型能量分析器的离子规和四极质谱计的性能

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Experimental Setup and Standardization of a Continuous Flow Stable Isotope Mass Spectrometer for Measuring Stable Isotopes of Carbon,Nitrogen and Sulfur in Environmental Samples

We present here the experimental setup and standardization of a newly acquired stable isotope ratio mass-spectrometer (Isoprime 100, Isoprime^® UK) coupled with elemental analyzer (Pyrocube, Elementar^®-Germany) in a continuous flow mode, for the measurements of C, N and S isotopes in a variety of natural as well as synthetic organics and sulfur containing solid samples. We have calibrated our instrument using a suite of certified international standards supplied by International Atomic Energy Agency Vienna and cross-checked against several in-house laboratory standards used by other institutions of international repute. A synthetic organic compound Sulfanilamide was continuously used along with international standards to develop an in-house internal laboratory standard for the accurate and precise isotopic measurements. Important components contributing to the overall uncertainty of the isotopic measurements such as blank contributions, amount effect and response of mass-spectrometric current against thermal conductivity detector were performed using several aliquots of ε-Amino-n-caproic acid and sulfanilamide (in-house) standards. Both short and long term variabilities in the measure isotopic data were assessed using our in-house laboratory standard Sulfanilamide. Overall estimated uncertainties of C, N and S isotopic measurements are better than 0.2, 0.2 and 0.3 ‰, respectively; which are well within the recommended limits of aforementioned isotopic data.     

电感耦合等离子体质谱在长寿命放射性核素分析中的应用

电感耦合等离子体质谱(Inductively Coupled Plasma Mass Spectrometer,ICP-MS)具有灵敏度高、检出限低、线性动态范围宽和可以进行多元素同时测定及同位素比测量等优点,是一种具有广阔前景的痕量(超痕量)无机多元素分析技术.ICP-MS检测半衰期大于几百年的放射性核素优于放射计数...     

Analysis of Carbendazim in Agricultural Samples by Laser Desorption and REMPI Time-of-Flight Mass Spectrometry

A method has been developed for the analysis of carbendazim in agricultural samples. This has been accomplished by the combination of laser desorption with resonance-enhanced multi-photon ionization (REMPI) coupled to time-of-flight mass spectrometry detection. After the optimization of the experimental conditions and the location of the resonant wavelength of the substance, several samples of pepper extract enriched with carbendazim were analyzed, finding a detection limit of the same order of magnitude as that of current GC and HPLC techniques, but with higher sensitivity and faster sample preparation.     

四极质谱计灵敏度与离子源参数关系的实验研究

本文通过改变QMS4 2 2型四极质谱计离子源的发射电流、阴极电压和聚焦电压等参数值 ,测量了质谱计灵敏度的相应变化 ,给出并分析了实验结果。实验结果表明 ,对质谱计离子源参数进行调节 ,可以优化质谱计的灵敏度并使之达到最大值