离子阱颗粒质谱研究进展

随着质谱技术的不断发展,对超高质量颗粒物质的分析已经成为质谱领域研究的一个重要方向.离子阱颗粒质谱(particle ion trap mass spectrometry)作为用于完整颗粒质量分析的有利工具,拓展了质谱技术在巨大颗粒物质量分析中的应用范围.本文对离子阱颗粒质谱仪器的研究进展及其在各个领域的应用进行了综述,并展望了离子阱颗粒质谱未来的发展趋势.     

同位素质谱和无机质谱

本文是《分析试验室》定期评述中“同位素质谱和无机质谱”的第四篇评述，评述的范围是１９９４年１１月至１９９６年１０月我国气体同位素质谱，热电离同位素质谱，加速器质谱，火花源质谱，电感耦合等离子体质谱，辉光放电质谱，同位素稀释质谱，二次离子质谱，激光共振电离子飞行时间质谱，电子探针，质子探针，激光探针和它们在地学，核科学，环境科学，材料学，计理学，医学和生命科学中的应用，引用文献１４９篇。     

The use of mass defect in modern mass spectrometry

Mass defect is defined as the difference between a compound's exact mass and its nominal mass. This concept has been increasingly used in mass spectrometry over the years, mainly due to the growing use of high resolution mass spectrometers capable of exact mass measurements in many application areas in analytical and bioanalytical chemistry. This article is meant as an introduction to the different uses of mass defect in applications using modern MS instrumentation. Visualizing complex mass spectra may be simplified with the concept of Kendrick mass by plotting nominal mass as a function of Kendrick mass defect, based on hydrocarbons subunits, as well as slight variations on this theme. Mass defect filtering of complex MS data has been used for selectively detecting compounds of interest, including drugs and their metabolites or endogenous compounds such as peptides and small molecule metabolites. Several strategies have been applied for labeling analytes with reagents containing unique mass defect features, thus shifting molecules into a less noisy area in the mass spectrum, thus increasing their detectability, especially in the area of proteomics. All these concepts will be covered to introduce the interested reader to the plethora of possibilities of mass defect analysis of high resolution mass spectra. Copyright © 2012 John Wiley & Sons, Ltd.     

Computational principles of determining and improving mass precision and accuracy for proteome measurements in an Orbitrap

Precision proteomics requires high-resolution and high mass accuracy peptide measurements. The Orbitrap instrument achieves excellent resolution on a chromatographic time scale and its design is favorable for very high mass accuracy. Here we describe how mass precision for each peptide increases successively by considering all associated measurements, starting from the MS peak and proceeding to its chromatographic elution profile, isotope envelope, and stable isotope pair in SILAC measurements. We extract peptide charge pairs to perform nonlinear recalibration of the Orbitrap mass scale through spline interpolation. The deviation of mass values determined from charge pairs is used to convert mass precision to mass accuracy for subsequent database search. The corrected mass precision is consistent with the mass accuracy independently determined by database identification. Individual mass deviations range from below 100 ppb for peptides with many associated mass measurements and good signal intensities to low ppm for peptides with few mass measurements and signals close to the noise level. This extremely high and individualized mass accuracy is equivalent to a substantial increase in database identification score.     

A collinear tandem time-of-flight mass spectrometer for infrared photodissociation spectroscopy of mass-selected ions

An apparatus based on collinear tandem time-of-flight mass spectrometer has been designed for the measurement of infrared photodissociation spectroscopy of mass-selected ions in the gas phase.The ions from a pulsed laser vaporization supersonic ion source are skimmed and mass separated by a Wiley-McLaren time-of-flight mass spectrometer.The ion of interest is mass selected,decelerated and dissociated by a tunable IR laser.The fragment and parent ions are reaccelerated and mass analyzed by the second time-of-flight mass spectrometer.A simple new assembly integrated with mass gate,deceleration and reacceleration ion optics was designed,which allows us to measure the infrared spectra of mass selected ions with high sensitivity and easy timing synchronization.     

Comparison of electron ionization mass spectra of some organic compounds (MW < 200 Da) recorded on mass spectrometers of various types

Low-resolution electron ionization mass spectra recorded on various types of mass spectrometers (time-of-flight, quadrupole, and three-dimensional ion trap) were compared. A model mixture of 10 organic compounds (MW < 200 Da) was analyzed by gas chromatography-mass spectrometry. Pure mass spectra of analytes were extracted using the AMDIS software. The best repeatability was achieved for the time-of-flight mass spectrometer. The mass spectra recorded by a quadrupole and a time-of-flight mass spectrometer were quite similar. In the case of these instruments, library search using a commercial mass spectral data base (NIST’05) gave satisfactory result for each analyte (rank 1 or 2 in the “hit list”; Match > 900). In some cases, the mass spectra of model compounds recorded by the ion trap mass spectrometer differed in intensity of certain mass spectral peaks (but not in the set of peaks) from the mass spectra presented in the library and from the experimental mass spectra recorded by the time-of-flight and quadrupole instruments.     

精确质量数在单四极杆质谱定性分析农药中的应用

利用MassWorks软件对GC/MS采集的目标农药谱图经过校正后,实现了在单位分辨率质谱上测定6种农药化合物的精确质量数,质量误差小于20mDa;在精确质量数基础上,进一步采用同位素峰形校正检索技术(CLIPs), 实现了对目标农药分子式的准确识别,建立了在单位分辨率质谱上准确测定农药小分子化合物的方法,提升了单位分辨率质谱的定性能力。通过对丙草胺及哒螨灵二种农药的质谱碎片所获得的MassWorks精确质量数及元素组成推导其质谱碎裂机理, 通过对碎片的精确质量数测定可提高对目标物定性的准确性。     

MPAI (mass probes aided ionization) method for total analysis of biomolecules by mass spectrometry.

We have designed and synthesized various mass probes, which enable us to effectively ionize various molecules to be detected with mass spectrometry. We call the ionization method using mass probes the "MPAI (mass probes aided ionization)" method. We aim at the sensitive detection of various biological molecules, and also the detection of bio-molecules by a single mass spectrometry serially without changing the mechanical settings. Here, we review mass probes for small molecules with various functional groups and mass probes for proteins. Further, we introduce newly developed mass probes for proteins for highly sensitive detection.     

A discussion on mass resolution in secondary ion mass spectrometry

Mass resolution is a very important parameter for mass spectrometry. It is necessary to compare the mass resolution between the newly developed TOF-SIMS and the conventionally high-performance magnetic SIMS. However, the definitions of mass resolution for these two types of instruments are quite different. Whether it is possible to compare mass resolution and how to do such comparison is a challenge. This problem was raised officially during the 2012 ISO/TC 201 meeting at Tampa, Florida, the United States and the long-term cooperation with ISO started afterwards. The definition of mass resolution is one of the most important and fundamental problems for mass spectrometry and should attract significant attention. Here, some detail discussions on mass resolution as well as the related experimental studies in the past few years, including the collaborations with ISO/TC 201/SC6 and SC1 are summarized. This summary covers the common problem for almost all the current existing and still used definitions of mass resolution. A reasonable new definition for mass resolution considering the peak shape or resolution function has been proposed, which has also been confirmed by using experimental studies of the mass resolution comparison between TOF and magnetic SIMS. This study lays a foundation for the future mass resolution comparisons between different mass spectrometry.     

Exact mass measurement of product ions for the structural confirmation and identification of unknown compounds using a quadrupole time-of-flight spectrometer: a simplified approach using combined tandem mass spectrometric functions

This article describes a simple method to perform lock mass corrected accurate mass measurements in tandem mass spectrometry (MS/MS) with a quadrupole time-of-flight (Q-TOF) mass spectrometer. The experimental approach consists of using the protonated molecule of a known compound, which is measured in a MS/MS function using low collision energy (no fragmentation), as mass calibrator. The unknown compound is acquired in MS/MS mode albeit using high collision energy. After the acquisition, the two MS/MS spectra of unknown and mass calibrator are combined, and the fragments of the unknown are lock mass corrected by using the protonated molecule of the mass calibrator. To prove this concept, 10 compounds were analyzed using this approach, the fragments interpreted and, where possible, related to structural data available in the literature. All the unequivocally assigned fragments were accurately mass measured with mass errors within appropriate limits, i.e. for m/z values <200 with a mass tolerance of 3 mDa while for m/z > 200 the mass tolerance is expressed as 10 ppm.