Quantitative analysis of nitro-polycyclic aromatic hydrocarbons in PM_2.5 samples with graphene as a matrix by MALDI-TOF MS

In this work, we developed a novel quantitative analysis method for detecting nitropolycyclic aromatic hydrocarbons (nitro-PAHs) in PM_2.5 samples with graphene as a matrix using MALDI-TOF MS. A good linearity was obtained for the typical four nitro-PAHs, namely 1-nitropyrene (1-NP), 2-nitrofluorene (2-NFL), 6-nitrochrysene (6-NC) and 9-nitroanthracene (9-NA) with the correlation coefficient better than 0.985 by means of 9-nitroanthracene-d₉ as the internal standard. The average recoveries of this method were from 69.2% to 119.4%, and the inter-day precisions were less than 12.3% with intra-day precisions less than 20.7%. The limits of detection for 1-NP, 2-NFL, 6-NC and 9-NA were 0.74, 8.04, 2.67 and 2.31 ng μL^-1, respectively. We have validated the practicality by the analysis of nitro-PAHs in PM_2.5 samples collected during haze weather in Taiyuan of China. The mass concentrations of Σ-nitropyrene, Σ-nitrofluorene, Σ-nitrochrysene and Σ-nitroanthracene on the collected PM_2.5 samples were detected at levels of 0.38 to 3.04 ng m^-3, 0.21 to 0.43 ng m^-3, 0.19 to 2.38 ng m^-3, and 9.55 to 16.52 ng m^-3, respectively. The present method proved to be a good candidate for simple, fast and eco-friendly determination of nitro-PAHs by using MALDI-TOF MS coupled with an internal standard method.