Laser ionization mass spectrometry of nonvolatile samples

Hardin, E. D.; Vestal, Marvin L.

doi:10.1021/ac00232a045

Cited by 77 publications

(23 citation statements)

References 23 publications

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“…Vestal and coworkers reported that non-resonant desorption/ionization of non-volatile compounds led to a dominance of alkali cationized species over protonated ones. 27,28 In practical MALDI experiments, the two processes usually coexist and compete. The competition between protonation and cationization is evident in the so-called 'matrix suppression effect'.…”

Section: Introductionmentioning

confidence: 99%

Matrix‐dependent cationization in MALDI mass spectrometry

Zhang¹,

Zenobi²

2004

J. Mass Spectrom.

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The matrix dependence in cationization processes, the competition between cationization and protonation and the question of whether gas-phase cation transfer or attachment of free cations dominates in matrix-assisted laser desorption/ionization mass spectrometry were studied. Two different sample preparation methods were employed, the dried-droplet sample preparation and a mixture of solid matrix, analyte and salt. The latter ensures that the formation of cation adducts takes place in the gas phase. By monitoring the suppression of matrix signals for different matrices, it was found that matrices with high gas-phase metal ion binding energies require high analyte concentrations for matrix suppression to occur. By comparing the mass spectra obtained using sinapinic acid or sinapinic methyl ester as a matrix, a correlation between cationization and deprotonation of matrix molecules was found. It is also demonstrated that attachment of free gas-phase cations, rather than cation transfer from the cationized matrix, is the predominant process in cationization.

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Section: Introductionmentioning

confidence: 99%

Matrix‐dependent cationization in MALDI mass spectrometry

Zhang¹,

Zenobi²

2004

J. Mass Spectrom.

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“…Taking into account the pioneering works of several research groups in the early 1980s [1][2][3][4][5][6][7][8][9], which investigated direct laser desorption/ionization of organic materials, we first tried to analyze our peptide samples without any substrate by depositing the peptide solution directly on the stainless steel MALDI plate. The results were very promising in terms of sensitivity and detection mass range but the low mass part of the spectra was exhibiting a lot of signals ( Figure 3).…”

Section: Preliminary Ldi Analysesmentioning

confidence: 99%

“…The results gathered from synthetic peptide cocktails indicated that LDI mass spectrometry on silica gel or alumina constitutes a promising complementary method to MALDI in proteomics for peptide mass fingerprinting. [1][2][3][4][5][6][7][8][9] was investigated by Siuzdak and collaborators using porous silicon as the substrate [10]. This desorption/ionization on porous silicon (DIOS) mass spectrometry [10] allows the analysis of various compounds, such as small organic molecules [11], amino acids [12], peptides [13], and fatty acids [14].…”

mentioning

confidence: 99%

“…Otherwise, silicon powders (5 to 50 nm particle size) were investigated as a substitute to DIOS chips to make the overall sample preparation simpler and safer [18]. Provided that the appropriate powder preparation was performed (including particle etching by HF, oxidation by HNO 3 , and derivatization of the generated SiOH groups), such silicon nanopowder method was found to exhibit the same characteristics as DIOS mass spectrometry.…”

mentioning

confidence: 99%

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Laser desorption/ionization mass spectrometry on porous silica and alumina for peptide mass fingerprinting

Shenar

Martinez

Enjalbal

2008

J. Am. Soc. Mass Spectrom.

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We investigated a variant of desorption/ionization on porous silicon (DIOS) mass spectrometry utilizing an aqueous suspension of either porous silica gel or porous alumina (pore size of 60 and 90 Å, respectively). Laser desorption/ionization (LDI) from samples directly deposited on a stainless steel surface without any inorganic substrates was also achieved. Synthetic peptides designed to cover large sequence diversity constituted our model compounds. Sample preparation, including material conditioning, peptide solubilization, and deposition protocol onto standard matrix-assisted laser desorption/ionization (MALDI) probe, as well as ionization source tuning were optimized to perform sensitive reproducible LDI analyses. The addition of either a cationizing agent or an alkali metal scavenger to the sample suspension allowed modification of the ionization output. Comparing hydrophilic silica gel to hydrophobic reversed-phase silica gel as well as increasing material pore size provided further insights into desorption/ionization processes. Furthermore, mixtures of peptides were analyzed to probe the spectral suppression phenomenon when no interfering organic matrix was present. The results gathered from synthetic peptide cocktails indicated that LDI mass spectrometry on silica gel or alumina constitutes a promising complementary method to MALDI in proteomics for peptide mass fingerprinting. [19]. These LDI methods, sometimes referred to as "matrix-free", produce mass spectra that exhibit less matrix ions in the low mass range compared with the chemical noise generated by the organic matrices used in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. Such chemical noise that usually pollutes the low mass range of MALDI mass spectra and that may complicate the detection of small molecules is less pronounced in the DIOS mass spectra.Nevertheless, the drawback of such an approach is in the preparation of the silicon material. To present adequate physical properties [20], silicon surfaces are conditioned via a galvanostatic etching procedure from Si wafer to produce pores with nanometer diameters. Commercially available ready-to-use DIOS-chips can also be mounted on modified MALDI plates [20]. Otherwise, silicon powders (5 to 50 nm particle size) were investigated as a substitute to DIOS chips to make the overall sample preparation simpler and safer [18]. Provided that the appropriate powder preparation was performed (including particle etching by HF, oxidation by HNO 3 , and derivatization of the generated SiOH groups), such silicon nanopowder method was found to exhibit the same characteristics as DIOS mass spectrometry.Porous silicon is a material that presents (1) a large active surface and (2) a strong absorbance in the UV range. Such a form of silicon was thus found particularly suitable for LDI mass spectrometry with irradiation at 337 nm, the pore size and the surface chemical nature being the most important parameters as stated by Siuzdak and coworkers in their early publications on DIOS [20...

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“…Recent experiments of Hardin and Vestal [20] point to a different mechanism of ion generation in which [M +Alkali]+ ions are formed via decomposition of desorbed clusters in the gas phase. The above experiments do not support such a mechanism even a sputtering of small particles of the sample material has been observed under various conditions of laser and electrical heating of samples.…”

Section: During the [M-fmentioning

confidence: 99%

Cationization by Alkali Ion Attachment in Laser Desorption Mass Spectrometry

Stoll

Röllgen

1982

Zeitschrift Für Naturforschung A

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The formation of quasimolecular ions by alkali ion attachment in laser desorption mass spectrometry has been investigated by using a CW CO2 laser. For molecules such as sucrose the desorption of preformed ions could be excluded. Evidence is presented for the ionization by alkali ion attachment in the gas phase. Quasimolecular ions of organic salts were found to result from cationization reactions in the gas phase and from surface reactions. Very fast cation exchange reactions have been discovered for salts and acids impinging on alkali ion emitting surfaces.

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Laser ionization mass spectrometry of nonvolatile samples

Cited by 77 publications

References 23 publications

Matrix‐dependent cationization in MALDI mass spectrometry

Matrix‐dependent cationization in MALDI mass spectrometry

Laser desorption/ionization mass spectrometry on porous silica and alumina for peptide mass fingerprinting

Cationization by Alkali Ion Attachment in Laser Desorption Mass Spectrometry

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