Evolved Gas Analysis by Mass Spectrometry

Abstract: Periodic publications have been published that address advances in evolved gas analysis techniques, because the correct interpretation for the mechanism of a thermally induced reaction, involving the formation of gaseous species, is strongly dependent on the characterization of the evolved products.

When the nature of volatile products released by a substance subjected to a controlled-temperature program are online determined, the results allow one to prove a supposed reaction, either under isothermal or under heating conditions.

Very recent analytical applications of evolved gas analysis performed by mass spectrometry, selected among those published in 2012 and 2013, are collected in this review.     

Mass Spectrometry,Review of the Basics: Electrospray,MALDI, and Commonly Used Mass Analyzers

Abstract

Mass spectrometry (MS) has progressed to become a powerful analytical tool for both quantitative and qualitative applications. The first mass spectrometer was constructed in 1912 and since then it has developed from only analyzing small inorganic molecules to biological macromolecules, practically with no mass limitations. Proteomics research, in particular, increasingly depends on MS technologies. The ability of mass spectrometry analyzing proteins and other biological extracts is due to the advances gained through the development of soft ionization techniques such as electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI) that can transform biomolecules into ions. ESI can efficiently be interfaced with separation techniques enhancing its role in the life and health sciences. MALDI, however, has the advantage of producing singly charges ions of peptides and proteins, minimizing spectral complexity. Regardless of the ionization source, the sensitivity of a mass spectrometer is related to the mass analyzer where ion separation occurs. Both quadrupole and time of flight (ToF) mass analyzers are commonly used and they can be configured together as QToF tandem mass spectrometric instruments. Tandem mass spectrometry (MS/MS), as the name indicates, is the result of performing two or more sequential separations of ions usually coupling two or more mass analyzers. Coupling a quadrupole and time of flight resulted in the production of high-resolution mass spectrometers (i.e., Q-ToF). This article will historically introduce mass spectrometry and summarizes the advantages and disadvantages of ESI and MALDI along with quadrupole and ToF mass analyzers, including the technical marriage between the two analyzers. This article is educational in nature and intended for graduate students and senior biochemistry students as well as chemists and biochemists who are not familiar with mass spectrometry and would like to learn the basics; it is not intended for mass spectrometry experts.     

Slurry Nebulization in Plasmas for Analysis of Inorganic Materials

Abstract

This review summarizes and discusses the preparation of slurries for analysis of inorganic materials by inductively coupled plasma optical emission spectrometry (ICP‐OES) and inductively coupled plasma mass spectrometry (ICP‐MS). Details about the grinding step for slurry preparation, the stabilization of slurries, and the calibration strategies are critically discussed. Typical applications described in the literature and the state‐of‐the‐art including advantages and limitations of slurry analysis are presented.     

Glow Discharge as a Tool for Surface and Interface Analysis

Abstract

This review article focuses on the analytical capabilities of glow discharge optical emission spectrometry (GD‐OES) and mass spectrometry (GD‐MS) to perform compositional depth profiling (GD‐CDP). The properties of the Grimm‐type glow discharge as well as basic processes of sputtering are described and their influence on the GD as a surface and interface analytical tool are discussed. A series of examples from recent literature ranging from computer hard disks to molecular monolayers on copper substrates are presented to illustrate the excellent depth resolution that can be achieved with GD surface analytical techniques. The conditions for obtaining nanometer or even atomic‐layer depth resolution are discussed. Following this introduction is the possibilities of the technique a selection of applications principally chosen from our laboratories, demonstrating that GD‐OES and GD‐MS can be successfully employed as an analytical tool assisting the development of new materials and coatings. The applications cover common industrial tasks such as heat treatments, studies of diffusion processes at interfaces, and electrochemical depositions for biocompatible material. However, limitations and known artifacts are also discussed.     

Raising the bar on-bead: Efficient on-resin synthesis of α-conotoxin LvIA

α4/7-Conotoxin LvIA is an isoform-selective inhibitor of the α3β2 nicotinic acetylcholine receptor. An efficient strategy for the synthesis of this toxin is critical to advancing its utility as a probe for receptor function and as a potential pharmaceutical lead target. On-resin methods for peptide synthesis offer potential synthetic advantages; however, strategies for on-resin formation of multiple disulfides have historically been low-yielding. Here, we harness the reactivity of the Allocam protecting group and employ a 3-amino acid spacer strategy to synthesize α4/7-conotoxin LvIA via three different on-resin strategies, each of which results in an isolated yield higher than previous fully on-resin approaches.     

Evidence for the Existence of (SiP6H2)2– and its Homologs as Examples of Binary Nortricyclane‐Type Zintl Anions

The extraction of stoichiometric ternary K/Si/P, K/Ge/P, and K/Si/As solid mixtures with en/crypt‐222 afforded compounds with binary anions of the respective groups 14/15 elemental combination. Although the analysis of the products turned out to be extremely difficult owing to their intrinsically poor crystallinity and low solubility, we have evidence that one of them contains (SiP₆H₂)^2– anions. Preliminary data from the two other compounds indicate the existence of the heavier Ge/P and Si/As variants as well. The combination of all analytical results, including X‐ray crystallography, energy‐dispersive X‐ray (EDX) spectroscopy, electrospray ionization mass spectrometry (ESI‐MS), and nuclear magnetic resonance (NMR) spectroscopy, point towards the named composition of the anions and their doubly protonated nature. By this, they represent the first binary Zintl anions of the Si/P and Si/As elemental combination and complement the recent endeavors to synthesize binary Zintl anions of the light(er) p‐block elements. We discuss our attempts to elucidate the clusters' identity and provide our results as the most probable interpretation of the data, additionally corroborated by quantum chemical analyses.     

Development of a PRiME cartridge purification method for rapid determination of malachite green and leucomalachite green in Chinese softshell turtle

A high‐throughput PRiME (process, robustness, improvements, matrix effects, ease of use) sample purification procedure was developed to simplify the multiple steps of traditional SPE in extracting the malachite green and leucomalachite green in Chinese softshell turtle (Pelodiscus sinensis). The sample loading volume, extracting solvent type, and pH value of the employed PRiME hydrophilic‐lipophilic balance cartridge for sample purification were optimized to be 3 mL, acetonitrile, and pH 5, respectively. In comparison with traditional SPE, the PRiME process is cost‐effective, solvent‐saving, and simple to operate, which only consists of a passing through step without traditional sorbent conditioning and impurity washing. Afterward, eluate was analyzed by ultra‐performance liquid chromatography‐tandem mass spectrometry, and the proposed method was validated for linearity (R² > 0.9992), intraday precision (2.44–3.22%), interday precision (3.28–6.58%), sensitivity (LOD ≤ 0.18 μg/kg and, LOQ ≤ 0.60 μg/kg), and recovery (88.7–94.1%, RSD < 6.79%). The results indicated that the PRiME technique can simplify the sample preparation procedure by avoiding the tedious steps, such as conditioning, washing, etc. It would be of significant interest for environmental and food safety applications in the market of Chinese softshell turtle and related products.     

A novel approach for protein identification from complex cell proteome using modified peptide mass fingerprinting algorithm

A unique peptide based search algorithm for identification of protein mixture using PMF is proposed. The proposed search algorithm utilizes binary search and heapsort programs to generate frequency chart depicting the unique peptides corresponding to all proteins in a proteome. The use of binary search program significantly reduces the time for frequency chart preparation to ～2 s for a proteome comprising ～23 000 proteins. The algorithm was applied to a three‐protein mixture identification, host cell protein (HCP) analysis, and a simulation‐generated data set. It was found that the algorithm could identify at least one unique peptide of a protein even in the presence of fourfold higher concentration of another protein. In addition, two HCPs that are known to be difficult to remove were missed by MS/MS approach and were exclusively identified using the presented algorithm. Thus, the proposed algorithm when used along with standard proteomic approaches present avenues for enhanced protein identification efficiency, particularly for applications such as HCP analysis in biopharmaceutical research, where identification of low‐abundance proteins are generally not achieved due to dynamic range limitations between the target product and HCPs.     

Bacillus licheniformis peptidoglycan characterization by CZE–MS: Assessment with the benchmark RP‐HPLC‐MS method

Peptidoglycan or murein is an essential polymer found in bacterial cell wall. It is a dynamic structure that is continuously remodeled or modified during bacterial cell growth or in presence of cell wall stresses. These modifications are still poorly understood mainly due to the peptidoglycan, which is rather non‐soluble, and the difficulties to separate the hydrophilic glycopeptides (muropeptides) by reversed phase liquid chromatography, generated by the enzymatic digestion using mutanolysin, an N‐acetyl‐muramidase, cleaving the β_1→4 bound between N‐acetylglucosamine and N‐acetylmuramic acid. Here, we report the use of CZE–MS for an easy and fast screening of muropeptides generated by the action of muramidase on the Bacillus licheniformis cell wall. Electron transfer and CID–MS were also used to unambiguously identify and localize the presence or the absence of amidation and acetylation moieties on muropeptide variants. The reference method to analyse muropeptides by reversed phase chromatography was also tested and the advantages and disadvantages of both methods were evaluated.     

一种刺松藻来源的硫酸阿拉伯聚糖的制备及特征结构表征

刺松藻(Codium fragile)经水提-醇沉获得粗多糖, 进一步将刺松藻粗多糖(CFP) 通过Q-Sepharose Fast Flow(QFF) 阴离子交换柱纯化得到6个多糖组分CFP1CFP6, 其中, 在CFP6中发现纯度较高的阿拉伯聚糖. 采用高效凝胶渗透色谱与十八角激光散射仪联用法和1-苯基-3-甲基-5-吡唑啉酮(PMP)柱前衍生高效液相色谱法对CFP6的分子量及单糖组成进行了分析. 结果表明, CFP6是一种分子量为79290的多糖, 由阿拉伯糖(Ara)和半乳糖(Gal)组成, 二者摩尔比为14.8:1.0. 通过多维核磁共振波谱、 液相色谱-质谱联用及二级质谱等方法对CFP6的糖苷键连接方式及其寡糖序列结构进行表征, 进一步阐明了该复杂多糖的特征结构. 经判断, CFP6主链由Ara组成, 通过 β-(1→3)糖苷键连接, 在Ara的C2位存在分支结构, 硫酸基位于Ara的C4或C2位.