Simultaneous Determination of 36 Kinds of Polycyclic Aromatic Hydrocarbons and Their Derivatives in Groundwater by Gas Chromatography-Mass Spectrometry

Samples of shallow groundwater were collected and stored at 4℃ in a refrigerator according to DD 2008-01. 1.000 0 L of the water sample was taken, and extracted for 10 min with 60 mL of a mixed extracting solvent of n-hexane and dichloromethane (1+1), after successive addition of 20.0 g of NaCl and 100 μL of 1.0 mg·L^-1 standard solution of mixed substitutes. After the 2 phases were separated, the organic phase was separated and preserved, and the water phase was extracted twice further with 30 mL of n-hexane for each extraction. The 3 extracts were combined and evaporated under swirling until its volume was concentrated to 2-3 mL, the evaporation was continued by N₂-blowing to concentrate the solution to a volume ca. 0.8 mL. 100 μL of the 2.0 mg·L^-1 mixed internal standard solution was added and the volume of the solution was made up to 1.0 mL with n-hexane. Rxi-5Sil MS capillary chromatographic column was selected for GC separation, under temperature elevation program by choosing 65℃ as the initial temperature. In MS analysis, EI ionization source was used, and mode of full-scanning was adopted for qualification while the mode of SIM for quantification. As shown by the results, linear relationships between values of peak area and mass concentration of the 36 polycyclic aromatic hydrocarbons and their derivatives were found in definite ranges, with detection limits (3S/N) in the range of 1.3-8.8 ng·L^-1. Test for recovery by standard addition method was made on the base of blank water sample, giving results in the range of 71.1%-120%, and RSDs (n=5) ranged from 1.2% to 9.7%.