Study on Separation of Polycyclic Aromatic Hydrocarbons in Soils for Compound-specific Carbon Isotope Analysis

XIE Man-man; LIU Mei-mei; WANG Shu-xian; LING Yuan; SUN Qing

doi:10.15898/j.cnki.11-2131/td.202109280131

XIE Man-man, LIU Mei-mei, WANG Shu-xian, LING Yuan, SUN Qing. Study on Separation of Polycyclic Aromatic Hydrocarbons in Soils for Compound-specific Carbon Isotope Analysis[J]. Rock and Mineral Analysis, 2021, 40(6): 962-972. DOI: 10.15898/j.cnki.11-2131/td.202109280131

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Study on Separation of Polycyclic Aromatic Hydrocarbons in Soils for Compound-specific Carbon Isotope Analysis

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BACKGROUNDTracing the source of polycyclic aromatic hydrocarbons (PAHs) by the compound-specific carbon isotope is becoming increasingly popular. For precise carbon isotope analysis, a pretreatment process is required to reduce co-outflow and unresolved complex mixture (UCM). Some existing studies require more instrumentation, such as high-performance liquid chromatography (HPLC). In addition, little attention has been paid to PAHs with a ring number less than 3.OBJECTIVESTo establish a good separation method of 16 PAHs for meeting the requirements of compound-specific carbon isotope analysis.METHODSThe effects of solid phase extraction (SPE) cartridges with amino and silica fillers were compared, and 10 eluent solvents were used on the separation, purification and enrichment effects of PAHs. Gas chromatography (GC) was used to test the separation and purification effect, and gas chromatography-isotope ratio mass spectrometry (GC-IRMS) was used to analyze compound-specific carbon isotopes.RESULTSMore than 20% of the naphthalene and acenaphthene in the amino cartridge cannot be completely separated from the alkanes and unresolved peaks. The silica gel SPE cartridge has better impurity removal and separation effects than the amino cartridge. Choosing 1000mg/6mL silica gel SPE cartridge, using 6mL n-pentane to elute UCM and alkanes, and 5mL n-pentane-dichloromethane (70:30, V/V) to elute PAHs, and GC to conduct a preliminary inspection of the separation and purification effect, and GC-IRMS for individual carbon isotope analysis. The recovery of 16 kinds of PAHs was 79%-128%, the relative standard deviation was 2%-13% (1σ, n=6), and the analysis accuracy of the single carbon isotope ratio (δ¹³C) was 0.1‰-0.75‰.CONCLUSIONSThe method greatly reduces the interferences of co-outflow and UCM to compound-specific carbon isotope analysis of PAHs, especially the low cyclic PAHs. No significant carbon isotope fractionation of PAHs is observed during purification, which satisfies compound-specific carbon isotope analysis requirements.

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Study on Separation of Polycyclic Aromatic Hydrocarbons in Soils for Compound-specific Carbon Isotope Analysis

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