AN ION-TO-PHOTON CONVERSION DETECTOR FOR MASS-SPECTROMETRY

An ion-to-photon conversion detector (IPD) for time-of-flight mass spe ctrometry was studied and tested with ions produced by matrix-assisted laser desorption-ionization. The detector consisted of a conversion s urface located at the end of the drift tube of a time-of-flight mass s pectrometer and, behind it, a head-on photomultiplier tube. Fluorescen t organic scintillator materials like Bu-PBD t-buthylphenyl)-5-(4-biph enylyl)-1,3,4-oxidiazole] were found to be the most efficient converte rs of those materials tested. Similar mass resolutions were found with the ion-to-photon detector and standard microchannel plates in a line ar time-of-flight instrument. The background noise of the IPD was more intense than with microchannel plates. Slow unfocused ions are suspec ted to contribute to this noise. Test analytes as large as 70 000 Da c ould be measured with the IPD. Even with no secondary particle convers ion surface in front of the IPD, masses up to approximately 20 000 Da may be more efficiently detected with the IPD than the MCP. For higher masses, a conversion dynode should be considered for increased signal . (C) 1997 Elsevier Science B.V.