The influence of polyatomic primary ion chemistry on matrix effects in secondary ion mass spectrometry analysis

Alnajeebi, Afnan M.; Vickerman, John C.; Lockyer, Nicholas P.

doi:10.1002/rcm.8265

Cited by 9 publications

(5 citation statements)

References 44 publications

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“…More than half of compounds, detected in the frozen hydrated state, are not detectable above the noise in the freeze-dried sample (compounds denoted with an asterisk in Supplementary Table 2). Water has a low gas phase basicity (665 kJ/mol) and acts as a matrix facilitating proton transfer for ionization. − Water can also stabilize and trap both the cation and anion to reduce the ion suppression by salts . Furthermore, we found that polar molecules (low Log P ) are, generally, more strongly enhanced.…”

Section: Resultsmentioning

confidence: 77%

Cryo-OrbiSIMS for 3D Molecular Imaging of a Bacterial Biofilm in Its Native State

et al. 2020

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Section: Resultsmentioning

confidence: 77%

Cryo-OrbiSIMS for 3D Molecular Imaging of a Bacterial Biofilm in Its Native State

et al. 2020

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“…On this basis, it is suggested that in the impact site some type of concerted mechanism occurs between the energized water cluster and the analyte molecules to enhance the protonation process. It seems that close to an aqueous environment is created in the emission zone, and this idea has been supported by recent studies showing that the yield using water beams is very similar to the yield using argon cluster beams from analyte in a frozen hydrated matrix …”

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confidence: 76%

“…It seems that close to an aqueous environment is created in the emission zone, and this idea has been supported by recent studies showing that the yield using water beams is very similar to the yield using argon cluster beams from analyte in a frozen hydrated matrix. 39 These studies suggested that using the water cluster beam may have enhanced the ionization probability of the molecules studied to 10 −2 or above, a very encouraging result. A subsequent study applied 20 keV water cluster beams (H 2 O) n and what was termed "wet" argon cluster beams (an argon cluster beam dosed with water at a partial pressure just below 1 bar) to imaging a mouse brain tissue.…”

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confidence: 92%

“…There is also some evidence that the matrix effect is ameliorated. 39,29,40 Studies with (D 2 O) n cluster beams have shown that enhanced protonation in the low E/n regime does arise principally from the water molecules in the cluster. 30 The mechanism of water cluster ion yield enhancement is a matter of some speculation; however, it is possible to derive some insights by combining molecular dynamics (MD) modeling with empirical considerations 41−44 and the observations from our experiments.…”

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confidence: 99%

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Enhanced Ion Yields Using High Energy Water Cluster Beams for Secondary Ion Mass Spectrometry Analysis and Imaging

et al. 2019

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Previous studies have shown that the use of a 20 keV water cluster beam as a primary beam for the analysis of organic and bio-organic systems resulted in a 10−100 times increase in positive molecular ion yield for a range of typical analytes compared to C 60 and argon cluster beams. This resulted in increased sensitivity to important lipid molecules in the bioimaging of rat brain. Building on these studies, the present work compares 40 and 70 keV water cluster beams with cluster beams composed of pure argon, argon and 10%CO 2 , and pure CO 2 . First, as previously, we show that for E/nucleon about 0.3 eV/nucleon water and nonwater containing cluster beams generate very similar ion yields, but below this value, the water beams yields of BOTH negative and positive "molecular" ions increase, in many cases reaching a maximum in the <0.2 region, with yield increases of ∼10−100. Ion fragment yields in general decrease quite dramatically in this region. Second, for water cluster beams at a constant E/nucleon, "molecular" ion yield increases with beam energy and hence cluster size due to increased sputter yield (ionization probability is constant). Third, as a consequence of the increased ion yield and the improved focusability using high-energy cluster beams, imaging in the 1 μm spatial resolution region is demonstrated on HeLa cells and rat brain tissue, monitoring molecules that were previously difficult to detect with other primary beams. Finally, the suggestion that the secondary ion emission zone has quasi-aqueous character seems to be sustained.

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“…In secondary-ion mass spectrometry (SIMS), , the formation of molecular ions is a rather complex process and a complete theoretical understanding seems to still be missing . The formation and detection of large organic and biological molecules in SIMS was greatly improved by the use of gas-cluster ions as projectiles. − Under such irradiation conditions, intact molecular ions were found to be sputtered from the specimens’ surface, while the number of emitted fragment species was reduced substantially. − Still, ion yields were found to be typically very low. In sputtering, organic (positive) molecular ions emerge frequently as protonated species, [M + H] + , or cationized via the attachment of (alkali) metal ions, X, to the originally neutral molecule, [M + X] + . ,, Quite often, this approach led to enhanced SIMS ion yields or to the ability to detect molecular species from an organic substance at all. − While beneficial for many analyses, the processes leading to cationization have not been investigated for gas cluster ion beams.…”

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Optimized Alkali-Metal Cationization in Secondary Ion Mass Spectrometry of Polyethylene Glycol Oligomers with up to m/z 10000: Dependence on Cation Species and Concentration

et al. 2019

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In secondary ion mass spectrometry (SIMS), the detection of large organic molecules is accomplished using cluster ion bombardment. Ion formation often proceeds via cationization, through the attachment of (alkali) metal ions to the molecule. To study this process, the emission of secondary ions sputtered from polyethylene glycol (PEG) samples with molecular weights (MW) of 1000–10000 was examined. They were mixed with alkali-metal trifluoroacetic acid (X-TFA, where X = Li, Na, K, or Cs) in a wide range of concentrations to investigate the efficiency of cationization for 10 keV Ar2000 + cluster irradiation. Typically, cationized molecular ions [M + X]+ (with repeat units n of up to ∼250, corresponding roughly to m/z 11000) and some characteristic fragment species were observed in the mass spectra. For all alkali cations, the oligomer intensities increase strongly with the molecular composition ratios X-TFA/PEG in the samples, and values of 5–10 seem to be optimal. With increasing molecular weight, the intensity of oligomer ions relative to the total number of ions decreases; as the latter remains rather constant, this implies that more fragment species are formed. The ion yields (detected ions per primary ions) of cationized [M + Na]+ oligomers sputtered from a PEG decrease very strongly with their size n: from 5.2 × 10–6 at n = 21 (MW ∼ 1000) to 4.5 × 10–10 at n ∼ 245 (MW ∼ 11000). By contrast, the total yields Y tot + show only a small variation for these different specimens, from 1.3 × 10–5 to 3.7 × 10–5.

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The influence of polyatomic primary ion chemistry on matrix effects in secondary ion mass spectrometry analysis

Cited by 9 publications

References 44 publications

Cryo-OrbiSIMS for 3D Molecular Imaging of a Bacterial Biofilm in Its Native State

Cryo-OrbiSIMS for 3D Molecular Imaging of a Bacterial Biofilm in Its Native State

Enhanced Ion Yields Using High Energy Water Cluster Beams for Secondary Ion Mass Spectrometry Analysis and Imaging

Optimized Alkali-Metal Cationization in Secondary Ion Mass Spectrometry of Polyethylene Glycol Oligomers with up to m/z 10000: Dependence on Cation Species and Concentration

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