Mass Spectrometry Reviews最新文献

Dielectric barrier discharge ionization (DBDI) sources, employing low-temperature plasma, have emerged as sensitive and efficient ionization tools with various atmospheric pressure ionization processes. In this review, we summarize a historical overview of the development of DBDI, highlighting key principles of gas-phase ion chemistry and the mechanisms underlying the ionization processes within the DBDI source. These processes start with the formation of reagent ions or metastable atoms from the discharge gas, which depends on the nature of the gas (helium, nitrogen, air) and on the presence of water vapor or other compounds or dopants. The processes of ionizing the analyte molecules are summarized, including Penning ionization, electron transfer, proton transfer and ligand switching from secondary hydrated hydronium ions. Presently, the DBDI-MS methods face a challenge in the accurate quantification of gaseous analytes, limiting its broader application in biological, environmental, and medical realms where relative quantification using standards is inherently complex for gaseous matrices. Finally, we propose future avenues of research to enhance the analytical capabilities of DBDI-MS.

This review delves into the efficacy of utilizing bubbles to extract analytes into the gas phase, offering a faster and greener alternative to traditional sample preparation methods for mass spectrometry. Generating numerous bubbles in liquids rapidly transfers volatile and surface-active species to the gas phase. Recently, effervescence has found application in chemical laboratories for swiftly extracting volatile organic compounds, facilitating instantaneous analysis. In the so-called fizzy extraction, liquid matrices are pressurized with gas and then subjected to sudden decompression to induce effervescence. Alternatively, specifically designed effervescent tablets are introduced into the liquid samples. In situ bubble generation has also enhanced dispersion of extractant in microextraction techniques. Furthermore, droplets from bursting bubbles are collected to analyze non-volatile species. Various methods exist to induce bubbling for sample preparation. The polydispersity of generated bubbles and the limited control of bubble size pose critical challenges in the stability of the bubble-liquid interface and the ability to quantify analytes using bubble-based sample preparation techniques. This review covers different bubble-assisted sample preparation methods and gives practical guidance on their implementation in mass spectrometry workflows. Traditional, offline, and online approaches for sample preparation relying on bubbles are discussed. Unconventional bubbling techniques for sample preparation are also covered.

Ambient and direct mass spectrometry (MS) methods are becoming increasingly used for the rapid analysis of food, beverage and agricultural samples. Novel ionization approaches combined with targeted, or untargeted workflows provide analytical outcomes within a greatly reduced time period compared to traditional separation science coupled with MS detection. This review will provide an overview of atmospheric pressure ionization MS based techniques for analysis of food, beverage and agricultural samples, with an emphasis on direct and rapid analysis including ambient ionization. The review will be completed through presentation of relevant examples of the use of ambient ionization techniques for food and beverage analysis along with the authors perspectives for future challenges relevant to the field.

In the 1980s, researchers discovered the remarkable ability of electrospray plumes to effectively ionize gas-phase molecules via secondary ionization. Around 20 years later-coinciding with the ambient mass spectrometry revolution-secondary electrospray ionization (SESI) and extractive electrospray ionization (EESI) coupled to mass spectrometry were revisited and further developed to analyze complex mixtures of gas and aerosol samples in real-time yet with high sensitivity. During the past two decades, these mass spectrometric techniques have been applied across a broad range of applications, such as the detection of illicit drugs, environmental aerosol analysis, and a series of metabolomic studies through the analysis of volatiles emitted from living organisms. This review offers a comprehensive overview of the progress of SESI and EESI applications since their emergence. Finally, we discuss the opportunities, challenges, along with future directions of SESI and EESI techniques.

One of the great triumphs of mass spectrometry-based peptide and protein characterization is the characterization of their modifications as most modifications have a characteristic mass shift. What happens when the modification does not change the mass of the peptide? Here, the characterization of several peptide and proteins modifications that do not involve a mass shift are highlighted. Protein and peptide synthesis on ribosomes involves L-amino acids; however, posttranslational modifications (PTMs) can convert these L-amino acids into their D-isomers. As another example, nonenzymatic PTM of aspartate leads to the formation of three different isomers, with isoaspartate being the most prevalent. Both modifications do not alter the mass of the peptide and yet can have profound impact on the physicochemical characteristics of the peptide. Several MS and ion mobility techniques are highlighted, as are other methods such as chromatography, enzymatic enrichment, and labeling. The challenges inherent to these analytical methods and prospective developments in bioinformatics and computational strategies are discussed for these zero-dalton PTMs.

Mass spectrometry (MS) is a powerful analytical technique that typically involves sample preparation and online analytical separation before MS detection. Traditional methods often face bottlenecks in sample preparation and analytical separation, despite the rapid detection capabilities of MS. This review explores the integration of electrokinetic manipulations directly with the ionization step to enhance MS performance, focusing on methods that eliminate or simplify sample preparation and separation processes. Techniques such as paper spray, electrophoresis in nanoelectrospray ionization (nESI) emitters, induced nESI, counterflow gradient electrofocusing, and in-syringe electrokinetics are highlighted for their ability to combine extraction and ionization in a single step, significantly improving throughput. The review delves into the use of electric fields during sample preparation and separations for these methods, demonstrating the efficiency of electrophoretic methods in driving extractions, crude separations, desalting, and enhanced sensitivity. The integration of these methods directly with MS ionization aims to enhance the analytical capabilities of mass spectrometry, while reducing costs and increasing throughput relative to traditional approaches.

Cancer is the leading cause of death worldwide characterized by patient heterogeneity and complex tumor microenvironment. While the genomics-based testing has transformed modern medicine, the challenge of diverse clinical outcomes highlights unmet needs for precision oncology. As functional molecules regulating cellular processes, proteins hold great promise as biomarkers and drug targets. Mass spectrometry (MS)-based clinical proteomics has illuminated the molecular features of cancers and facilitated discovery of biomarkers or therapeutic targets, paving the way for innovative strategies that enhance the precision of personalized treatment. In this article, we introduced the tools and current achievements of MS-based proteomics, choice of discovery and targeted MS from discovery to validation phases, profiling sensitivity from bulk samples to single-cell level and tissue to liquid biopsy specimens, current regulatory landscape of MS-based protein laboratory-developed tests (LDTs). The challenges, success and future perspectives in translating research MS assay into clinical applications are also discussed. With well-designed validation studies to demonstrate clinical benefits and meet the regulatory requirements for both analytical and clinical performance, the future of MS-based assays is promising with numerous opportunities to improve cancer diagnosis, treatment, and monitoring.

Mass spectrometry imaging (MSI) technologies are widely used today to study the in situ spatial distributions for a variety of analytes. As these technologies advance, the pursuit of higher resolution in MSI has intensified. The limitation of direct desorption/ionization is its insufficient ionization, posing a constraint on the advancement of high-resolution MSI technologies. The introduction of postionization process compensates the low ionization efficiency caused by sacrificing the desorption area while pursuing high spatial resolution, resolving the conflict between high spatial resolution and high sensitivity in direct desorption/ionization method. Here, we discuss the sampling and ionization steps of MSI separately, and review the postionization methods in MSI according to three different sampling modes: laser sampling, probe sampling, and ion beam sampling. Postionization technology excels in enhancing ionization efficiency, boosting sensitivity, mitigating discrimination effect, simplifying sample preparation, and expanding the scope of applicability. These advantages position postionization technology as a promising tool for biomedical sciences, materials sciences, forensic analysis and other fields.