Evaluation of the Isotope Ratio Performance of an Axial Time-of-Flight ICP Mass Spectrometer

The isotope ratio performance of an axial time-of-flight ICP mass spectrometer (Renaissance TOF-ICPMS, LECO Corp.) was evaluated. The isotope ratio precision, expressed as the relative standard deviation (RSD) for 10 successive measurements, was evaluated using multielement standard solutions with analyte concentrations of 50-500 μg/L. The influence of the acquisition time per replicate measurement was studied by varying it between 0.5 and 300 s. For an acquisition time of 30 s per replicate and an elemental concentration of 500 μg/L, typical isotope ratio precisions of ≤0.05% RSD were obtained. The fact that this isotope ratio precision can be obtained for many ratios simultaneously is an especially attractive feature of TOF-ICPMS. In contrast to what was expected, increasing the acquisition time per replicate to values of >30 s resulted in a slightly deteriorated isotope ratio precision. At short acquisition times (<10 s), isotope ratio precisions similar to, or better than, the best values ever reported for quadrupole-based instruments were obtained. The latter observation remained valid when working with transient signals of corresponding duration. Mass discrimination was observed to be analogous to that observed with other types of ICPMS instrumentation (～1% per mass unit at midmass). The accuracy attainable was evaluated by comparing Pb isotopic results for a "natural" Pb standard solution obtained by TOF-ICPMS with those obtained by thermal ionization mass spectrometry.     

The Precise Measurement of Current Ratios

The development of the current comparator, a three-winding current ratio transformer, is reviewed and its characteristics as an alternating current ratio standard are analyzed. Particular attention is given to the use of magnetic shielding and its effect on the accuracy and usefulness of the device. Some error characteristics of three types of audio-frequency current comparators are given and possible applications discussed. These include the calibration of current transformers and impedance comparisons. The adaptation of this device to dc operation is made possible by modulation techniques. A 20 000-ampere self-balancing direct current comparator, designed specifically for the calibration in situ of transductors or direct current transformers, is described. The application of this comparator to the calibration of shunts at high currents also is discussed and some results presented.     

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.     

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。     

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。     

三级差分抽气分子束质谱装置的设计和研究

研制了具有三级涡轮分子泵差分抽气系统的分子束质谱装置 ,该装置在 1330 0Pa典型气体采样压力下 ,三级差分抽气区的压力分别达到 5× 10 - 1,3× 10 - 3,1 2× 10 - 4Pa。利用该装置 ,已成功地实现了对活性离子物种N 和N 2 的“原位”检测     

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。     

真空紫外光电离飞行时间质谱仪间接在线检测二恶英前体物

利用自主研发的高灵敏度真空紫外光电离飞行时间质谱仪(VUV-TOFMS),对一氯苯、1,2-二氯苯和1,2,4-三氯苯3种氯苯类二恶英前体物进行在线检测,对聚氯乙烯燃烧产生的模拟烟气、一氯苯的实时浓度进行在线监测,并对燃烧产生的二恶英浓度进行初步量化分析。结果表明:VUV-TOFMS间接实现了对垃圾焚烧二恶英产物的检测;得到了较准确的母体离子信号峰,信号强度与实际浓度的线性关系良好,一氯苯、1,2-二氯苯和1,2,4-三氯苯的检出限(体积分数)分别达到4.7×10-9、8.7×10-9、11.9×10-9。     

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.     

Measurement of Stratospheric Chromatic Scintillation with the AMON-RA Balloonborne Spectrometer

The balloonborne instrument AMON (which is a French acronym for Absorption par les Minoritaires Ozone et NO(x)) has been modified to record chromatic scintillation during stellar occultation by the Earth's atmosphere. A 14-channel spectrophotometer with a sampling rate of 10 Hz was added, and the modified instrument, AMON-RA, performed successful measurements of the setting star Alnilam during the third European Stratospheric Experiment on Ozone (THESEO) project. Unambiguous records of the chromatic scintillation were obtained, to our knowledge for the first time from above the atmosphere, and some of its basic properties are reported. The properties of atmospheric structures that are responsible for this chromatic scintillation were found to be consistent with those of previous monochromatic measurements performed from space. A maximum chromatic delay of 2.5 s was observed for widely different wavelengths.     

Mg–Gd–Y–Zn稀土镁合金应变调节机制研究

目的 在微观尺度上研究Mg–5.4Gd–1.8Y–1.5Zn合金的应变调节机制。方法 将拉伸试样变形至应变为6%,采用基于互相关分析的高分辨EBSD技术测量材料内部的刚体转动张量以及几何必需位错密度。结果 Mg–Gd–Y–Zn合金主要由基面<a>位错以及锥面<c+a>位错调节应变,即使在软取向晶粒内,锥面<c+a>位错也会大量出现。当发生基面–基面位错的滑移转移与基面–锥面位错的滑移转移时,相邻两晶粒滑移系之间的Luster–Morris因子很高(>0.78)。结论 随着不同滑移系施密特因子的升高,晶粒内的位错密度逐渐降低。这一反常现象可以归因于硬取向晶粒变形需消耗更多的应变能,而这部分应变能以位错密度的形式储存在晶粒内。     

Noise-Enhanced Measurement of Weak Doublet Spectra with a Fourier-Transform Spectrometer and a 1-Bit Analog-to-Digital Converter

We demonstrate an efficient noise dithering procedure for measuring the power spectrum of a weak spectral doublet with a Fourier-transform spectrometer in which the subthreshold interferogram is measured by a 1-bit analog-to-digital converter without oversampling. In the absence of noise, no information is obtained regarding the doublet spectrum because the modulation term s(x) of its interferogram is below the instrumental detection limit B, i.e., |s(x)| < B, for all path difference x values. Extensive numerical experiments are carried out concerning the recovery of the doublet power spectrum that is represented by s(x) = (s(0)/2)exp(-pi(2)x(2)/beta)[cos(2pif(1)x) + cos(2pif(2)x)], where s(0) is a constant, beta is the linewidth factor, and ?f? = (f(1) + f(2))/2. Different values of ?f?, s(0), and beta are considered to evaluate thoroughly the accuracy of the procedure to determine the unknown values of f(1) and f(2), the spectral linewidth, and the peak values of the spectral profiles. Our experiments show that, even for short observation times, the resonant frequencies of s(x) could be located with high accuracy over a wide range of ?f? and beta values. Signal-to-noise ratios as high as 50 are also gained for the recovered power spectra. The performance of the procedure is also analyzed with respect to another method that recovers the amplitude values of s(x) directly.     

开放式离子源-单四极杆质谱仪研究与应用

针对目前开放式离子源与质谱仪连接的趋势,研制出介质阻挡放电离子源、解吸附电喷雾离子源2种开放式离子源,改进了大气压接口-单四极杆质谱仪的接口,通过离子源和质谱仪的连接实验,实现了对去疼片、罗丹明B样品的原位分析.该仪器为原位快速分析提供了一种简单有效的工具.     

IRMS和SNIF-NMR技术在食品检测中的应用及展望

食品真伪、掺假掺杂的检测鉴别是食品安全领域的关注热点。本文介绍了同位数比质谱仪法(IRMS)和点特异性天然同位素分馏核磁共振技术(SNIF-NMR)的基本科学原理,综述了它们在蜂蜜、酒、果汁、油脂等食品掺假检测方面的应用,展望了其可能的新的应用,为采用该两种检测技术制定检测鉴别地沟油和其他食品的标准提供有益的思路。     

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。     

精密时间测量技术

时间间隔的测量是时频信号研究的基础,已经被越来越广泛的应用于科学试验和工程实践等各个领域,测量精度的提高是迫切需要解决的问题。本文介绍了脉冲计数法以及用于测量其原理误差的国内外常用精密时间间隔测量方法,分析了各自的优缺点以及误差,并指出其发展趋势,为新方法的研究提供参考。     

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。     

用Bessel-Box型能量分析器的离子规和四极质谱计的性能

Ｔｈｅｌｏｗｅｒｌｉｍｉｔｏｆｔｈｅｐｒｅｓｓｕｒｅｍｅａｓｕｒｅｍｅｎｔｏｆａｎｉｏｎｉｚａｔｉｏｎｇａｕｇｅｉｓｍａｉｎｌｙｄｅｔｅｒｍｉｎｅｄｂｙｔｈｒｅｅｆａｃｔｏｒｓ :ｔｈｅｓｏｆｔＸ ｒａｙｅｆｆｅｃｔ ,ｅｌｅｃｔｒｏｎｓｔｉｍｕｌａｔｅｄｄｅｓｏｒｐｔｉｏｎ (ＥＳＤ) ,ａｎｄｏｕｔｇａｓｓｉｎｇｆｒｏｍｔｈｅｇａｕｇｅ .Ｍａｎｙｔｙｐｅｓｏｆｉｏｎｉｚａｔｉｏｎｇａｕｇｅｓｈａｖｅｂｅｅｎｄｅｖｅｌｏｐｅｄｔｏｒｅｄｕｃｅｔｈｅｓｅｆａｃｔｏｒｓ .Ａ ｍｏｎｇｔｈｅｍｔｈｅｇａｕｇｅ…     

空间行波管排气过程中残余气体的质谱分析

电真空器件内残余气体直接影响其阴极的发射能力与寿命。本文利用高灵敏度四极质谱仪监测了空间行波管在整个排气过程中的残余气体,对各阶段气体成分及含量进行了分析。结果表明:烘烤前,水为主要气体,占80%。前期擦拭用无水乙醇易污染真空系统;升温过程中氢迅速增多,当烘烤温度达到220℃时,H₂成为系统中主要气体;整个烘排过程H₂的分压小于10^-3Pa,其余气体分压均小于10^-4Pa;烘烤结束后,H₂分压为2.4×10^-8Pa,占74%。H₂O分压为6×10^-9Pa,占20%;离子泵与吸气剂泵组可有效抽除残余气体,且对H₂的抽速高于对其他气体抽速;另外,质谱仪自身会放出H₂、H₂O、CH₄、CO₂等气体,在真空系统压力达到10^-9Pa范围时,质谱仪自身放气已不可忽略。