Estimation of useful yield in surface analysis using single photon ionisation

King, B. V.; Pellin, Michael J.; Moore, Jean K.; Veryovkin, I. V.; Savina, M. R.; Tripa, C. E.

doi:10.1016/s0169-4332(02)00636-0

Cited by 24 publications

(31 citation statements)

References 6 publications

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“…The IE of most organic molecules is <~10 eV (24). The IEs of selected organic compounds (homologous series) are depicted in Figure 1a as a function of the molecular weight; the photon energies of common VUV sources are also shown.…”

Section: Spi Fundamentalsmentioning

confidence: 99%

Light and Molecular Ions: The Emergence of Vacuum UV Single-Photon Ionization in MS

Hanley¹,

2009

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Thanks to recent technological advances and singlephoton ionization's (SPI's) ability to detect all organics,Because the human eye does not detect IR radiation, we cannot see a warm object in the dark without an IR camera or other "transformation method". MS has the same problem: it cannot directly detect the objects of intereststhe analyte moleculessbut only their ionized counterparts. Therefore, the transformation methods that ionize the analyte molecules are of particular importance to MS. The invention of new ionization methods such as MALDI or ESI for MS detection of biomolecules has had an enormous influence on the development of MS and its applications in analytical chemistry.However, many ionization methods result in the formation not only of intact molecular ions but also of ion fragments. This is particularly true for electron impact (EI) ionization, the classical ionization method for smaller molecules ranging in mass up to ∼500 Da. EI uses electrons of 70-eV kinetic energy, near where maximal ionization efficiency occurs, 1 which makes it a "hard" ionization technique because the analytes are heavily fragmented upon ionization. The molecular peak is often barely visible in the mass spectra of labile compounds, although the fragment patterns do supply information about the presence of distinct functional groups in the investigated molecules. Furthermore, the fragment patterns of unknown substances can be used for a statistically based identification by comparison with EI-MS library data. The benefits of the latter feature made MS with EI the routine spectrometric detection method for GC. However, the frequent absence of information on the molecular weight of labile compounds is a severe disadvantage of EI, hampering the identification of unknowns. Furthermore, for complex mixtures of organic compounds, EI-MS requires a preseparation method such as GC; otherwise, the overlapping complex fragment patterns cannot be deconvoluted into mass spectra of individual compounds.These shortcomings of EI have led to a continuing demand for robust fragmentation-free or "soft" ionization methods for MS. Several soft ionization techniques have been developed, including methods based on chemical ionization (CI), field ionization (FI), and photoionization (PI). More recently, MALDI and ESI emerged and became the dominant soft ionization methods for polar

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Section: Spi Fundamentalsmentioning

confidence: 99%

Light and Molecular Ions: The Emergence of Vacuum UV Single-Photon Ionization in MS

Hanley¹,

2009

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“…Certain small molecules have sufficiently low ionization energies to allow 7.87 eV single photon ionization, including many fused ring aromatics, tryptophan, and tertiary amines. However, most laser desorbed species display ionization energies >7.87 eV and require 10.5 eV VUV to undergo single photon ionization [35,15]. Most amino acids, carboxylic acids such as saturated fatty acids with aliphatic carbon chains and phospholipids are excellent candidates for 10.5 eV single photon ionization since they display ionization energies >7.87 eV [36].…”

Section: Resultsmentioning

confidence: 99%

Laser desorption VUV postionization MS imaging of a cocultured biofilm

Bhardwaj

Moore²,

Cui

et al. 2012

Anal Bioanal Chem

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Laser desorption postionization mass spectrometry (LDPI-MS) imaging is demonstrated with a 10.5 eV photon energy source for analysis and imaging of small endogenous molecules within intact biofilms. Biofilm consortia comprised of a synthetic Escherichia coli K12 coculture engineered for syntrophic metabolite exchange are grown on membranes, then used to test LDPI-MS analysis and imaging. Both E. coli strains displayed many similar peaks in LDPI-MS up to m/z 650, although some observed differences in peak intensities were consistent with the appearance of byproducts preferentially expressed by one strain. The relatively low mass resolution and accuracy of this specific LDPI-MS instrument prevented definitive assignment of species to peaks, but strategies are discussed to overcome this shortcoming. The results are also discussed in terms of desorption and ionization issues related to the use of 10.5 eV single photon ionization, with control experiments providing additional mechanistic information. Finally, 10.5 eV LDPI-MS was able to collect ion images from intact, electrically insulating biofilms at ~100 μm spatial resolution. Spatial resolution of ~20 μm was possible, although a relatively long acquisition time resulted from the 10 Hz repetition rate of the single photon ionization source.

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“…Previous report reveals that most of the components in the plume are neutral for the pulse energy of the infrared desorption laser (~1.2 eV) is far below the ionization threshold of any potential analytes. 24 Therefore, a large fraction of molecular analytes can be ionized by single photon of VUV radiation at 118 nm (ca. 18,19 In the ionization step, gas-phase molecules in the desorbed plume of neutrals are typically ionized by either VUV single photon ionization (VUV-SPI) or ultraviolet resonant enhanced multiphoton ionization (UV-REMPI).…”

Section: 1principle Of Ldpi-ms Methodsmentioning

confidence: 99%

Direct and fast detection of chlorothalonil in soil samples using laser desorption VUV single photon post-ionization mass spectrometry

Liu

Zhu

et al. 2015

Anal. Methods

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Wide and abusive applications of fungicides (such as chlorothalonil) in agricultural production have caused various adverse effects on the environment, especially on the soil. Herein, a novel laser desorption VUV single photon postionization mass spectrometry (LDPI-MS) has been firstly applied to the direct and fast detection of chlorothalonil in soil. In the experiment, three different wavelength lasers were used as the ionization sources (SPI at 118 nm, REMPI at 266 nm and 355 nm) and the results showed that only SPI at 118 nm could achieve expected "soft" ionization. The limit of detection in 118 nm ionization was determined to be 0.5 pmol per spot, ca. 1 mg/kg of chlorothalonil in soil. Moreover, no other additives were needed to assistant desorption/evaporation of chlorothalonil from soil samples and the detecting process could be rapidly completed on the basis of a time-saving sample pretreatment. The results demonstrated that LDPI-MS method held a great potential for detecting real natural soil contaminated with chlorothalonil.

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Estimation of useful yield in surface analysis using single photon ionisation

Cited by 24 publications

References 6 publications

Light and Molecular Ions: The Emergence of Vacuum UV Single-Photon Ionization in MS

Light and Molecular Ions: The Emergence of Vacuum UV Single-Photon Ionization in MS

Laser desorption VUV postionization MS imaging of a cocultured biofilm

Direct and fast detection of chlorothalonil in soil samples using laser desorption VUV single photon post-ionization mass spectrometry

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