title: Fluorometric beam profiling of UV MALDI lasers.
abstract: The photon distribution (beam profile) of the laser as projected onto the sample is an important variable in matrix assisted laser desorption ionization mass spectrometry (MALDI-MS). Measurement of the beam profile is, therefore, an important factor within MALDI-MS. In this study a simple, low-cost fluorometric laser beam profiling technique is presented and applied in conjunction with MALDI-MS experiments. A comparison of the beam profile information afforded by a commercial system and the fluorometric method is carried out to determine the variation of beam profile for an Nd:YVO4 laser operated between 1 and 25 kHz. The beam profile information can be used, in conjunction with corresponding ion yields, to inform MALDI-MS experiments. The fluorometric beam profiling technique is used to obtain information about the beam dimensions as incident upon the MALDI-MS sample plate in-source. These values are compared with equivalent information obtained from ablation of thin film α-cyano-4-hydroxycinnamic acid (CHCA). In this study, area estimation by ablation provided a value 1.6 times smaller than that obtained by the fluorometric method, demonstrating the need for caution when measuring beam profile and, therefore, fluence, in MALDI-MS. ᅟ
authors.affiliation: PSIBS Doctoral Training Centre, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.
authors.forename: Rory T
authors.initials: RT
authors.lastname: Steven
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Palmer
authors.forename: Josephine
authors.initials: J
authors.lastname: Bunch