title: Matrix-enhanced secondary ion mass spectrometry (ME SIMS) using room temperature ionic liquid matrices.
abstract: Room temperature ionic liquids (ILs) have many applications including as matrices in MALDI. We wished to investigate the efficacy of ILs as matrices in time-of-flight secondary ion mass spectrometry and in mass spectrometric imaging (MS imaging). Two ILs derived from alpha-cyano-4-hydroxycinnamic acid (CHCA) were synthesized and tested using phospholipids, cholesterol, and peptides. The molecular ion intensities of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE), cholesterol, and bradykinin were greatly increased using IL matrices. Further, detection limits were also improved: for DPPC and DPPE detection, limits were at least 2 orders of magnitude better using IL matrices. However, these IL matrices were not effective for the enhancement of angiotensin I ions. The data also indicate that IL matrices are suitable for imaging MS. The IL matrices did not cause changes to the sample surface via matrix crystallization or other processes; no "hot spots" were observed in the mass spectra. As a demonstration, an onionskin membrane was imaged. In the matrix-enhanced MS images, ions characteristic of proteins and other biomolecules were observed which could not otherwise be observed. Clearly ionic liquids deserve further investigation in SIMS and MS imaging.
authors.affiliation: Department of Materials Science and Engineering, University of Texas at Dallas, 800 West Campbell Road, RL 10, Richardson, Texas 75080, USA.
authors.forename: Jennifer J D
authors.initials: JJ
authors.lastname: Fitzgerald
authors.forename: Paul
authors.initials: P
authors.lastname: Kunnath
authors.forename: Amy V
authors.initials: AV
authors.lastname: Walker
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000032:analysis; D001920:Bradykinin / Q000032:analysis; D006801:Humans; D007328:Insulin / Q000032:analysis; D052578:Ionic Liquids / Q000737:chemistry*; D057230:Limit of Detection; D013058:Mass Spectrometry / Q000379:methods*; D011092:Polyethylene Glycols / Q000032:analysis; D011522:Protons; D013696:Temperature
chemical_list: D007328:Insulin; D052578:Ionic Liquids; D011522:Protons; D015060:1,2-Dipalmitoylphosphatidylcholine; D011092:Polyethylene Glycols; D001920:Bradykinin