MALDI-TOF mass spectrometry of insoluble giant polycyclic aromatic hydrocarbons by a new method of sample preparation.

The insolubility of giant polycyclic aromatic hydrocarbons (PAHs) prevents their characterization by conventional analytical methods, which require a solubilization of the analyte. Laser desorption mass spectrometry may be used to analyze insoluble samples but is limited to relatively low molecular weights (approximately 2000), in the case of PAHs. To overcome this limitation, we applied MALDI-TOF mass spectrometry. Since MALDI sample preparation also requires solubility of analyte and matrix molecules, the sample preparation needed modification. The giant PAHs (>2000 Da) were investigated after using a new sample preparation, consisting of mechanically mixing analyte and matrix without any solubilization procedures. This solvent-free process allows insoluble compounds to be characterized. Furthermore, new organic molecules can be used as a matrix. Indeed, 7,7,8,8-tetracyanoquinodimethane, a new matrix with promising properties, has proven to be particularly suitable for the measurement of PAHs. Thanks to the successful characterization with MALDI-TOF mass spectrometry, the chemical design of giant PAHs, which was hindered until now for a lack of analytical methods, can now continue to develop.