Laser system for MALDI mass spectrometry
Mass spectrometry with lasers generates ions from analyte molecules by matrix assisted laser desorption for a variety of different mass spectrometric analysis procedures. The mass spectrometers with laser systems supply laser light pulses having at least two different pulse durations, and mass spectrometric measuring techniques use the laser light pulses of different durations. The duration of the laser light pulses allows the characteristics of the ionization of the analyte molecules, particularly the occurrence of the ISD (in-source decay) and PSD (post-source decay) types of fragmentation, whose fragment ion spectra supply different kinds of information, to be adapted to the analytic procedure.
1. A mass spectrometer, comprising a laser system that ionizes analyte molecules by matrix assisted laser desorption, where the laser system provides a plurality of laser light pulses of different durations and where the laser system delivers both a laser light pulse with a maximum duration of about one nanosecond, whose pulse duration and power is suited to the generation of spontaneous ISD (in-source decay) fragment ions of the analyte molecules, and also deliver a laser light pulse with a duration of at least three nanoseconds, whose pulse duration and power is suited to the generation of spectra of ergodic PSD (post-source decay) fragment ions.
2. The mass spectrometer of claim 1 , where the shortest laser light pulse is less than about one nanosecond in length.
3. The mass spectrometer of claim 1 , where the longest laser light pulse is greater than at least three nanoseconds in length.
4. The mass spectrometer of claim 1 , where the laser system supplies laser light pulses with two different, fixed pulse durations.
5. The mass spectrometer of claim 4 , where the laser system comprises two lasers.
6. The mass spectrometer of claim 1 , where the laser system supplies laser light pulses with pulse durations that are adjustable, either continuously or in discrete steps.
7. The mass spectrometer of claim 1 , where the laser system delivers laser light pulses whose power is time-modulated.
8. The mass spectrometer of claim 1 , where the laser system delivers laser light pulses that comprise either a single pulse or at least two successive individual pulses.
9. A method for ionization of the analyte molecules by matrix assisted laser desorption in a mass spectrometer with a laser system, comprising automatically adjusting the laser system to deliver both a laser light pulse with a maximum duration of about one nanosecond, whose pulse duration and power is suited to the generation of spontaneous ISD (in-source decay) fragment ions of the analyte molecules, and also deliver a laser light pulse with a duration of at least three nanoseconds, whose pulse duration and power is suited to the generation of spectra of ergodic PSD (post-source decay) fragment ions.
10. The method of claim 9 , where the laser system is adjusted to deliver short laser light pulses with a duration of less than about one nanosecond for spontaneous fragmentation of the analyte molecules, and to deliver longer laser light pulses with a duration of at least three nanoseconds for the generation of metastable analyte ions.
11. The method of claim 9 , wherein the longer laser light pulses comprise a series of at least two individual light pulses.