Federal Institute for Materials Research and Testing (BAM), Richard-Willstätter-Strasse 11, D-12489, Berlin, Germany.
Rapid Commun Mass Spectrom. 2014 Mar 15;28(5):489-98. doi: 10.1002/rcm.6810.
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.
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.
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.
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.
通过干燥液滴法制备的用于基质辅助激光解吸/电离飞行时间质谱（MALDI-TOF MS）的聚合物样品斑点通常显示出环状形成，同时可能伴随着基质和样品分子的分离以及聚合物同系物本身的分离。由于大多数样品斑点是通过这种简单快速的方法制备的，因此必须找到一种不发生这种分离的基质或样品制备方法。
制备了三种基于常用于 MALDI-TOF MS 的传统芳香族化合物的不同离子液体基质。通过（1）H NMR 光谱证明了离子液体的形成。应用 MALDI 成像质谱法来监测均匀性。
我们的结果表明，使用离子液体基质可以获得更好的样品斑点均匀性。可以多次采样而不会在质谱中出现明显差异。在质谱仪真空室中经常观察到的基质损失没有观察到。所需的激光辐照度降低，导致聚合物碎片减少。
离子液体基质可用于克服常规 MALDI 干燥液滴制备中常见的分离问题。均匀的样品斑点易于制备，在 MS 真空室中稳定，从而提高了 MALDI 的重现性。
