Stable Carbon Isotope Fractionation of Polycyclic Aromatic Hydrocarbons During the Sample Preparation Process

Stability and accuracy for determination of δ¹³C of polycyclic aromatic hydrocarbons (PAHs) were tested by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) with continuous and intermittent injection modes. The results showed that the peak area and peak separation degree were the main factors influencing the precision of δ¹³C data. The fractionation of stable carbon isotopes of PAHs during the sample pretreatment processes was also tested. The cleanup process with gel permeation chromatography (GPC), silica gel column, as well as rotatory evaporation, nitrogen purge and other enrichment process brought no significant isotope fractionation of PAHs. Isotope fractionation in cleanup processes with silica gel column was little larger than with GPC, but still within two standard deviation (2σ) range of the mean δ¹³C of PAHs from an unprocessed standard material. And the enrichment processes of rotatory evaporation and nitrogen purge produced a little isotope fractionation for all the measured δ¹³C of PAHs within 1σ range of the mean δ¹³C from the unprocessed standard material.