Efficient analysis of non-polar environmental contaminants by MALDI-TOF MS with graphene as matrix

In this Application Note, we describe, for the first time, the rapid analysis of hydrophobic compounds present in environmental contaminants, which includes polycyclic aromatic hydrocarbons (PAHs) and estrogen, by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) with the use of graphene as matrix. MALDI-TOF MS with conventional matrix has limitations in analyzing low-polarity compounds owing to their difficulty in ionization. We demonstrate that compared with conventional matrix, graphene displays higher desorption/ionization efficiencies for PAHs, and no fragment ions are observed. The method also holds potential in quantitative analysis. In addition, the ionization signal increases with the increasing number of benzene rings in the PAHs, suggesting that graphene binds to PAHs via π-π stacking interactions. Furthermore, graphene as adsorbent for solid-phase extraction of coronene from river water sample displays good performance with a detection limit of 10(-7) M. This work provides a novel and convenient method for analyzing low-polarity environmental contaminants by MALDI-TOF MS.