Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry using an inorganic particle matrix for small molecule analysis

✍ Scribed by Kinumi, Tomoya; Saisu, Takumi; Takayama, Mitsuo; Niwa, Haruki

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 112 KB
• Volume: 35
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/(sici)1096-9888(200003)35:3<417::aid-jms952>3.0.co;2-#

✦ Synopsis

Fine metal or metal oxide powder as an alternative to conventional organic matrices in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) has been utilized successfully for lower molecular mass analytes, poly(ethylene glycol) 200 (PEG 200) and methyl stearate. Eleven kinds of particle, Al, Mn, Mo, Si, Sn, SnO 2 , TiO 2 , W, WO 3 , Zn and ZnO, were evaluated. The analyte was mixed with a metal or metal oxide powder (inorganic matrix) with particle diameter of tens of micrometers and liquid dispersant, followed by application to the sample target. Using a commercial MALDI-TOFMS instrument equipped with an internal 337 nm pulsed nitrogen laser, the analytes, PEG 200 and methyl stearate, were ionized as the alkali metal ion adducted molecules [M Y Na] Y or [M Y K] Y when the inorganic matrices Mn, Mo, Si, Sn, TiO 2 , W, WO 3 , Zn or ZnO were used. In the case of an Al matrix, PEG 200 was ionized as [M Y K] Y , whereas methyl stearate was ionized as [M Y H] Y and [M Y Al] Y . These particles have potential as the matrix for MALDI. During our examination, however, only SnO 2 particles did not ionize either PEG 200 or methyl stearate. Based on our protocol, when TiO 2 powder was suspended with liquid paraffin, PEG 200 and methyl stearate gave their MALDI-TOF mass spectra with the lowest background noise and highest intensity. TiO 2 powder seemed to be a broad potential matrix for low molecular mass polar or non-polar analytes. The results suggested that bulk particles caused rapid heating/vaporization processes and ionized analyte molecules under irradiation with a pulsed UV laser. The present method can be readily applied to obtain the low background noise MALDI-TOF mass spectra of small-sized compounds.