Matrix-assisted laser desorption/ionization time-of-flight mass spectrometric imaging of synthetic polymer sample spots prepared using ionic liquid matrices.
BACKGROUND
Polymer sample spots for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) prepared by the dried-droplet method often reveal ring formation accompanied by possible segregation of matrix and sample molecules as well as of the polymer homologs itself. Since the majority of sample spots are prepared by this simple and fast method, a matrix or sample preparation method that excludes such segregation has to be found.


METHODS
Three different ionic liquid matrices based on conventionally used aromatic compounds for MALDI-TOF MS were prepared. The formation of ionic liquids was proven by (1) H NMR spectroscopy. MALDI-Imaging mass spectrometry was applied to monitor the homogeneity.


RESULTS
Our results show a superior sample spot homogeneity using ionic liquid matrices. Spots could be sampled several times without visible differences in the mass spectra. A frequently observed loss of matrix in the mass spectrometer vacuum was not observed. The necessary laser irradiance was reduced, which resulted in less polymer fragmentation.


CONCLUSIONS
Ionic liquid matrices can be used to overcome segregation, a typical drawback of conventional MALDI dried-droplet preparations. Homogeneous sample spots are easy to prepare, stable in the MS vacuum and, thereby, improve the reproducibility of MALDI.
Federal Institute for Materials Research and Testing (BAM), Richard-Willstätter-Strasse 11, D-12489, Berlin, Germany.
Stefan J
SJ
Gabriel
Dietmar
D
Pfeifer
Clemens
C
Schwarzinger
Ulrich
U
Panne
Steffen M
SM
Weidner
D002082:Butylamines; D003373:Coumaric Acids; D005021:Ethylamines; D005841:Gentisates; D052578:Ionic Liquids / Q000737:chemistry*; D009570:Nitriles; D011108:Polymers / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
C555195:2-((2E)-3-(4-tert-butylphenyl)-2-methylprop-2-enylidene)malononitrile; D002082:Butylamines; D003373:Coumaric Acids; D005021:Ethylamines; D005841:Gentisates; D052578:Ionic Liquids; D009570:Nitriles; D011108:Polymers; C073734:sinapinic acid; C032462:n-butylamine; C016162:triethylamine; C010925:2,5-dihydroxybenzoic acid