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RationaleThe developments of new ionization technologies based on processes previously unknown to mass spectrometry (MS) have gained significant momentum. Herein we address the importance of understanding these unique ionization processes, demonstrate the new capabilities currently unmet by other methods, and outline their considerable analytical potential. MethodsTheinletandvacuumionization methods of solvent‐assisted ionization (SAI), matrix‐assisted ionization (MAI), and laserspray ionization can be used with commercial and dedicated ion sources producing ions from atmospheric or vacuum conditions for analyses of a variety of materials including drugs, lipids, and proteins introduced from well plates, pipet tips and plate surfaces with and without a laser using solid or solvent matrices. Mass spectrometers from various vendors are employed. ResultsResults are presented highlighting strengths relative to ionization methods of electrospray ionization (ESI) and matrix‐assisted laser desorption/ionization. We demonstrate the utility of multi‐ionization platforms encompassing MAI, SAI, and ESI and enabling detection of what otherwise is missed, especially when directly analyzing mixtures. Unmatched robustness is achieved with dedicated vacuum MAI sources with mechanical introduction of the sample to the sub‐atmospheric pressure (vacuumMAI). Simplicity and use of a wide array of matrices are attained using a conduit (inletionization), preferably heated, with sample introduction from atmospheric pressure. Tissue, whole blood, urine (including mouse, chicken, and human origin), bacteria strains and chemical on‐probe reactions are analyzed directly and, especially in the case ofvacuumionization, without concern of carryover or instrument contamination. ConclusionsExamples are provided highlighting the exceptional analytical capabilities associated with the novel ionization processes in MS that reduce operational complexity while increasing speed and robustness, achieving mass spectra with low background for improved sensitivity, suggesting the potential of this simple ionization technology to drive MS into areas currently underserved, such as clinical and medical applications.
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Quantitative analysis of polycyclic aromatic hydrocarbons using high‐performance liquid chromatography‐photodiode array‐high‐resolution mass spectrometric detection platform coupled to electrospray and atmospheric pressure photoionization sources
Abstract Polycyclic aromatic hydrocarbons (PAHs) are common pollutants present in atmospheric aerosols and other environmental mixtures. They are of particular air quality and human health concerns as many of them are carcinogenic toxins. They also affect absorption of solar radiation by aerosols, therefore contributing to the radiative forcing of climate. For environmental chemistry studies, it is advantageous to quantify PAH components using the same analytical technics that are commonly applied to characterize a broad range of polar analytes present in the same environmental mixtures. Liquid chromatography coupled with photodiode array and high‐resolution mass spectrometric detection (LC‐PDA‐HRMS) is a method of choice for comprehensive characterization of chemical composition and quantification of light absorption properties of individual organic compounds present in the environmental samples. However, quantification of non‐polar PAHs by this method is poorly established because of their imperfect ionization in electrospray ionization (ESI) technique. This tutorial article provides a comprehensive evaluation of the quantitative analysis of 16 priority pollutant PAHs in a standard reference material using the LC–MS platform coupled with the ESI source. Results are further corroborated by the quantitation experiments using an atmospheric pressure photoionization (APPI) method, which is more sensitive for the PAH detection. The basic concepts and step‐by‐step practical guidance for the PAHs quantitative characterization are offered based on the systematic experiments, which include (1) Evaluation effects of different acidification levels by formic acid on the (+)ESI‐MS detection of PAHs. (2) Comparison of detection limits in ESI+ versus APPI+ experiments. (3) Investigation of the PAH fragmentation patterns in MS2experiments at different collision energies. (4) Calculation of wavelength dependent mass absorption coefficient (MACλ) of the standard mixture and its individual PAHs using LC‐PDA data. (5) Assessment of the minimal injected mass required for accurate quantification ofMACλof the standard mixture and of a multi‐component environmental sample.
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- Award ID(s):
- 2039985
- PAR ID:
- 10367525
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Journal of Mass Spectrometry
- Volume:
- 57
- Issue:
- 2
- ISSN:
- 1076-5174
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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