Consecutive Infrared Multiphoton Dissociations in a Fourier Transform Ion Cyclotron Resonance Mass Spectrometer

• Published in: Analytical chemistry (Washington) Vol. 69; no. 23; pp. 4735 - 4740
• Main Authors: Tonner, D. Scott, McMahon, Terrance B
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01-12-1997
• Subjects: Analytical chemistry; Chemistry; Exact sciences and technology; Instruments; Ions; Spectrometric and optical methods; Analysis method; Reaction path; Mass spectrometry MS/MS; Fragmentation pattern; Photodissociation; Infrared irradiation; Multiphoton ionization; Ion cyclotron resonance
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac970727e

Consecutive infrared multiphoton dissociations (IRMPD) may be observed in a Fourier transform ion cyclotron resonance mass spectrometer (FTICR). This is the IRMPD equivalent of previous MS n experiments using CID. This work presents a versatile technique, using a bistable shutter to gate ON and OFF a continuous-wave (CW) CO2 laser for multiple irradiation periods of 0.1−1000 s duration. Consecutive photodissociations, up to MS4, are demonstrated for the proton-bound dimer of diethyl ether and the resulting fragment ions. The photoproducts are formed close to the center of the FTICR cell, resulting in high product ion recovery efficiency. This differs from CID products, which are formed throughout the FTICR cell causing reisolation/detection problems. The fragmentation resulting from the use of low-intensity, CW, infrared laser radiation is shown to be much more energy selective than CID. Photodissociation of C2H5OH2 + ion produces the lowest energy product ion exclusively, even though the two product channels differ only by ∼5 kcal/mol. Low-energy CID, however, produces a mixture of C2H5 + and H3O+ products in the ratio of 1.3:1. Hence, the higher energy pathway (C2H5 +) is substantially favored. The current results indicate that this IRMPD MS n technique may be successfully applied to large biomolecules prepared by electrospray or MALDI.