A traceless clean-up method coupled with gas chromatography and mass spectrometry for analyzing polycyclic aromatic hydrocarbons in complex plant leave matrices
This study developed a traceless clean-up method combining solid phase extraction (SPE) with gas purge–microsyringe extraction (GP-MSE) to purify sample extracts for the determination of polycyclic aromatic hydrocarbons (PAHs) in plant leaves. SPE exhibited good purification performance for the removal of polar lipid, while the GP-MSE technique effectively eliminate low-volatile lipid hence realizing zero damage to instrument, and significantly improve the peak tailings. After ultrasonic extraction, the combined two-step clean-up procedure successfully removed over 99% of lipids from nineteen types of tree leaves, and PAHs from tree leaves were determined by GC-MS. The relative standard deviation (RSD) for intra-day (n=3) and inter-day (n=3) analysis of PAHs from spiked willow samples were 0.8% – 12.1% and 4.7% – 15.3%, respectively. The recoveries of PAHs from spiked willow extracts ranged from 74 to 90%, with an average of 86%. The method detection limit (MDL) of PAHs in tree leaves ranged from 0.1 to 4.9 ng g-1 dry weight. In conclusion, the clean-up method in this study realized the analysis of PAHs from plant leaves with high accuracy, sensitivity and reproducibility. Most importantly, the two-step purification method significantly minimizes damage to the GC-MS system particularly on the column and ion source, which is beneficial to ensure continuous analysis for a large number of samples with good performance.