Issues and opportunities in accelerator mass spectrometry for stable isotopes

Accelerator mass spectrometry (AMS) has developed in the last 30 years many notable applications to the spectrometry of radioisotopes, particularly in radiocarbon dating. The instrumentation science of trace element AMS (TEAMS) that analyzes stable isotopes, also called Accelerator SIMS or MegaSIMS, while unique in many features, has also shared in many of these significant advances and has pushed TEAMS sensitivity to concentration levels surpassing many competing mass spectroscopic technologies. This review examines recent instrumentation developments, the capabilities of the new instrumentation and discernable trends for future development.     

稳定同位素质谱技术在生态系统氮素循环中的应用

自然界中,氮的放射性同位素半衰期短,因此¹⁵N是唯一适用的天然示踪物。采用¹⁵N稀释或者富集技术,通过检测不同形态¹⁵N的丰度,能够较真实地了解陆地生态系统中氮素的固定、矿化、硝化和反硝化等过程。本工作简述了陆地生态系统中氮素循环的各个过程及¹⁵N 同位素分馏机制,简要介绍了稳定氮同位素的测定方法,系统论述了稳定氮同位素技术在生物固氮及土壤氮素转化过程中的研究现状,并在此基础上预测了该方法在国内氮素循环研究中的应用前景。     

Mass spectrometry in the biosynthetic and structural investigation of lignins

Lignin, a resistant cell-wall constituent of all vascular plants that consists of ether and carbon-linked methoxyphenols, is still far from being structurally described in detail. The main problem in its structural elucidation is the difficulty of isolating lignin from other wood components without damaging lignin itself. Furthermore, the high number and variegated forms of linkages that occur between the monomeric units and the chemical resistance of certain ether bonds limit the extent to which analytical and degradation procedures can be used to elucidate the lignin structure. Most of our present knowledge about the molecular structure of lignin is based on the analysis of monomers, dimers or, at the most, tetramers of degraded isolated lignins. Mass spectrometry (MS), which offers advantages in terms of speed, specificity, and sensitivity, has revealed to be a very powerful technique in the structural elucidation of lignins, in combination with the great number of chemical and thermal degradation methods available in the study of lignin. Moreover, the recent development of new ionization techniques in MS-electrospray ionization (ESI)-MS and matrix-assisted laser desorption/ionization (MALDI)-MS-has provided new possibilities to also analyze the undegraded lignin macromolecule.     

用MAT253同位素质谱仪测定氕氘混合气组分

To meet the need of the research on isotope effects of mixed hydrogen isotope gas, an analysis method of mixed hydrogen isotope composition was set up through introducing the molecule ionization quotient on MAT253 mass spectrometer. Some effect factors to quotient were examined and the method is used to determine 6 samples of different deuterium concentration. The results show that this method is effective for P2D2 mixed gas and it’s relative standard deviation is more low then 0.3%.     

同位素比值质谱与激光吸收光谱分析水中氢氧同位素方法的比较

氢氧稳定同位素在研究地球水循环过程中发挥着重要作用。本研究采用激光光谱法和高温热转换元素-同位素比值质谱法测定水样中氢同位素,采用激光光谱法和CO₂-H₂O平衡-同位素比值质谱法测定水样中氧同位素。结果表明：使用原理不同的两种方法测定地下水、海水和大气降水样品,测定的δ²H和δ¹⁸O值的精密度与准确度相当,激光光谱法以其快速高效、低成本、样品用量少占有优势;但使用这两种方法测定土壤抽提水样品时,激光光谱法测定δ¹⁸O值与真值的偏差为0.34‰,而质谱法测定的偏差小于0.10‰;激光光谱法测定δ2H值与真值的偏差为2.3‰,而质谱法测定的偏差小于0.6‰,说明质谱法的结果明显优于激光光谱法。     

Mass spectrometry in the proteome analysis of mature cereal kernels

In the last decade, the improved performance and versatility of the mass spectrometers together with the increasing availability of gene and genomic sequence database, led the mass spectrometry to become an indispensable tool for either protein and proteome analyses in cereals. Mass spectrometric works on prolamins have rapidly evolved from the determination of the molecular masses of proteins to the proteomic approaches aimed to a large‐scale protein identification and study of functional and regulatory aspects of proteins. Mass spectrometry coupled with electrophoresis, chromatographic methods, and bioinformatics tools is currently making significant contributions to a better knowledge of the composition and structure of the cereal proteins and their structure–function relationships. Results obtained using mass spectrometry, including characterization of prolamins, investigation of the gluten toxicity for coeliac patients, identification of proteins responsible of cereal allergies, determination of the protein pattern and its modification under environmental or stress effects, investigation of genetically modified varieties by proteomic approaches, are summarized here, to illustrate current trends, analytical troubles and challenges, and suggest possible future perspectives. © 2011 Wiley Periodicals, Inc. Mass Spec Rev 31:448–465, 2012     

用同位素质谱技术发现山西古风化壳型稀土金属矿床

对山西石炭纪铝土矿中钐 (Sm )和钕 (Nd)元素含量的化学制备和同位素质谱稀释分析方法进行了详细探讨 ,采用固体同位素质谱技术发现了山西古风化壳型稀土金属矿床。可能总稀土的强富集是在本区形成风化壳吸附型轻稀土金属矿床的主要成因。研究结果表明 :在山西沁源大峪和平陆曹川的稀土含量达到风化壳吸附型轻稀土金属和稀土铝土矿矿床工业指标。山西古风化壳型稀土金属矿床是在华北地区首次发现的稀土金属矿床。     

同位素稀释质谱法用于河水中钾的测量溯源性研究

本文简要介绍了化学测量溯源性和具有绝对测量性质的同位素稀释质谱法（IDMS）,并应用该法为国际测量评估计划（IMEP-9）河水样品中的钾提供可直接溯源到SI单位的标准值。     

Mass spectrometry in the quantitative analysis of therapeutic intracellular nucleotide analogs

Nucleoside analogs are widely used in anti‐cancer, anti‐(retro)viral, and immunosuppressive therapy. Nucleosides are prodrugs that require intracellular activation to mono‐, di‐, and finally triphosphates. Monitoring of these intracellular nucleotides is important to understand their pharmacology. The relatively involatile salts and ion‐pairing agents traditionally used for the separation of these ionic analytes limit the applicability of mass spectrometry (MS) for detection. Both indirect and direct methods have been developed to circumvent this apparent incompatibility. Indirect methods consist of de‐phosphorylation of the nucleotides into nucleosides before the actual analysis. Various direct approaches have been developed, ranging from the use of relatively volatile or very low levels of regular ion‐pairing agents, hydrophilic interaction chromatography (HILIC), weak anion‐exchange, or porous graphitic carbon columns to capillary electrophoresis and matrix‐assisted light desorption—time of flight (MALDI‐TOF) MS. In this review we present an overview of the publications describing the quantitative analysis of therapeutic intracellular nucleotide analogs using MS. The focus is on the different approaches for their direct analysis. We conclude that despite the technical hurdles, several useful MS‐compatible chromatographic approaches have been developed, enabling the use of the excellent selectivity and sensitivity of MS for the quantitative analysis of intracellular nucleotides. © 2010 Wiley Periodicals, Inc., Mass Spec Rev 30:321–343, 2011     

Mass spectrometry of the photolysis of sulfonylurea herbicides in prairie waters

This review of mass spectrometry of sulfonylurea herbicides includes a focus on studies relevant to Canadian Prairie waters. Emphasis is given to data gaps in the literature for the rates of photolysis of selected sulfonylurea herbicides in different water matrices. Specifically, results are evaluated for positive ion electrospray tandem mass spectrometry with liquid chromatography separation for the study of the photolysis of chlorsulfuron, tribenuron‐methyl, thifensulfuron‐methyl, metsulfuron‐methyl, and ethametsulfuron‐methyl. LC–MS/MS is shown to be the method of choice for the quantification of sulfonylurea herbicides with instrumental detection limits ranging from 1.3 to 7.2 pg (on‐column). Tandem mass spectrometry coupled with the use of authentic standards likewise has proven to be well suited for the identification of transformation products. To date, however, the power of time‐of‐flight MS and ultrahigh resolution MS has not been exploited fully for the identification of unknown photolysis products. Dissipation of the herbicides under natural sunlight fit pseudo‐first‐order kinetics with half‐life values ranging from 4.4 to 99 days. For simulated sunlight, radiation wavelengths shorter than 400 nm are required to induce significant photolytic reactions. The correlation between field dissipation studies and laboratory photolysis experiments suggests that photolysis is a major pathway for the dissipation of some sulfonylurea herbicides in natural Prairie waters. © 2009 Wiley Periodicals, Inc., Mass Spec Rev 29:593–605, 2010     

Advances in mass spectrometry for the identification of pathogens

Mass spectrometry (MS) has become an important technique to identify microbial biomarkers. The rapid and accurate MS identification of microorganisms without any extensive pretreatment of samples is now possible. This review summarizes MS methods that are currently utilized in microbial analyses. Affinity methods are effective to clean, enrich, and investigate microorganisms from complex matrices. Functionalized magnetic nanoparticles might concentrate traces of target microorganisms from sample solutions. Therefore, nanoparticle-based techniques have a favorable detection limit. MS coupled with various chromatographic techniques, such as liquid chromatography and capillary electrophoresis, reduces the complexity of microbial biomarkers and yields reliable results. The direct analysis of whole pathogenic microbial cells with matrix-assisted laser desorption/ionization MS without sample separation reveals specific biomarkers for taxonomy, and has the advantages of simplicity, rapidity, and high-throughput measurements. The MS detection of polymerase chain reaction (PCR)-amplified microbial nucleic acids provides an alternative to biomarker analysis. This review will conclude with some current applications of MS in the identification of pathogens.     

Mass spectrometry for the study of protein glycation in disease

The structural elucidation of advanced glycation end-product (AGE)-modified proteins and quantitative analysis of free AGEs have been successfully performed, by use of mass spectrometry (MS) in plasma and tissues of patients with AGE-related diseases, such as diabetes mellitus, uremia, cataract, and liver cirrhosis. Matrix-assisted laser desorption/ionization (MALDI)-MS made it possible to directly analyze the AGE-modified proteins such as albumin and IgG. However, because the direct structural analysis of intact AGE-modified proteins is often not easy due to the formation of broad and poorly resolved peaks, peptide mapping after enzymatic hydrolysis was introduced into the analysis of AGE-modified proteins and the site-specific analysis of defined AGEs by MALDI-MS. Liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) has been employed not only for the structural elucidation of enzymatically hydrolyzed AGEs-modified peptides but also for simultaneous quantification of free AGEs in plasma and tissues of patients. Based on many studies that use MS for the analysis of AGEs, there is no doubt as to the important role of protein-linked AGEs in several diseases.     

负热电离质谱法测量Os同位素组成的质量分馏校正

根据质量分馏校正和氧同位素干扰校正的原则 ,通过实践总结出一套处理数据的方法 ,包括不加稀释剂条件下采用美国 Finnigan MAT公司的推荐值 2 40 M/2 3 6M=3 .0 92 2 0 3 ,与本工作提出的归一化值 2 40 M/2 3 8M=1 .5 5 3 62 4进行质量分馏校正。理论上本实验室提出的归一化基准值适用于各种类型岩矿样品 ,该值与样品的 187Os/188Os比值无关。加稀释剂条件下采用循环迭代的方法 ,在每次迭代过程中得到新的归一化基准值 ,并进行氧同位素校正和质量分馏校正 ,最后得到样品的 Os含量和 187Os/188Os的值 ,实践表明通常情况下在 5～ 6次迭代后即可收敛 ,得到校正后的结果     

Mass spectrometry in the characterization of reactive metal alkoxides

Metal alkoxides are metal‐organic compounds characterized by the presence of M?O?C bonds (M = metal). Their chemistry seems to be, in principle, relatively simple but the number of possible reactant species arising as a consequence of their behavior is very remarkable. The physico‐chemical properties of metal alkoxides are determined by many different parameters, the most important ones being the electronegativity of the metal, the ramification of the ligand, and the acidity of the corresponding alcohol. Their reactivity makes them suitable and versatile candidates for many applications, including homogeneous catalysis, synthesis of new ceramic materials through the sol‐gel process and, recently, also for Cultural Heritage. Metal alkoxides are characterized by a strong tendency to give clusters and/or oligomers through oxo‐bridges. Mass spectrometry has been successfully employed for the characterization of metal alkoxides in the gas‐phase. Electron ionization (EI) allowed the assessment of the molecular weight and of the most relevant decomposition pathways giving information on the relative bond strength of differently substituted molecules. On the other hand, information on the reactivity in solution of these molecules have been obtained by electrospray ionization (ESI)‐matrix assisted laser desorption ionization (MALDI) experiments performed on their reaction products. These data were relevant to investigate the sol‐gel process. In this review, these aspects are described and the results obtained are critically evaluated. © 2016 Wiley Periodicals, Inc. Mass Spec Rev