M.W. Little, J.-K. Kim, K.K. Murray, “Two-laser infrared and ultraviolet matrix-assisted laser desorption/ionization,” J. Mass Spectrom.38 (2003) 772–777. doi:10.1002/jms.494.


Matrix‐assisted laser desorption/ionization (MALDI) was performed using two pulsed lasers with wavelengths in the IR and UV regions. A 10.6 µm pulsed CO2 laser was used to irradiate a MALDI target, followed after an adjustable delay by a 337 nm pulsed nitrogen laser. The sample consisted of a 2,5‐dihydroxybenzoic acid matrix and bovine insulin guest molecule. The pulse energy for both of the lasers was adjusted so that the ion of interest, either the matrix or guest ion, was not produced by either of the lasers alone. The delay time for maximum ion yield occurs at 1 µs for matrix and guest ions and the signal decayed to zero in ∼400 µs. A mechanism is presented for enhanced UV MALDI ion yield following the IR laser pulse based on transient heating.

Two-laser IR/UV MALDI
Schematic layout of the two-laser IR/UV MALDI experiments using a linear time-of-flight mass spectrometer (TOF MS). The infrared (IR) and ultraviolet (UV) lasers are directed at the same target spot from opposite sides of the instrument. The computer (PC) controls the delay generator (DG) and digital oscilloscope (DO).
Home-built linear TOF mass spectrometer
Linear time-of-flight mass spectrometer
Linear TOF MS source chamber
Linear time-of-flight mass spectrometer source chamber