Determination of Total Petroleum Hydrocarbons in Environmental Water by GC

For GC-determination of volatile petroleum hydrocarbons (VPHC) in environmental water, 40 mL of the water sample, after adjusting its acidity to pH<2.0 and cooling to 4℃, was used directly for GC analysis, and the purging and trapping technique for sample introduction was adopted. In the GC-determination of extractable petroleum hydrocarbons (EPHC), 500 mL of the water sample, was extracted twice with 15 mL of CH₂Cl₂ in each extraction. The extracts were combined and evaporated to less than 1.0 mL by N₂-blowing. CH₂Cl₂ was added to make its volume to 1.0 mL and it was used for GC-analysis. DB-5 capillary chromatographic column was used for GC-separation of both the VPHC and EPHC, and the FID was used for determination in both cases. The gasoline standard solution and diesel standard sample were used as primary standards in the above 2 analytical items respectively. In preparation of standard curves, values of total peak areas of the chromatographic peaks of compounds of C₆H₁₄ to C₁₀H₂₂ appeared in the retention time interval of 3.439 to 15.418 min (for VPHC), and of the chromatographic peaks of compounds of C₁₀H₂₈ to C₂₈H₅₈ appeared in the retention time interval of 9.027 to 40.479 min (for EPHC) were taken as the ordinate and values of their mass concentrations were taken as the abscissa. The linearity ranges found were between 0.018 to 0.25 mg·L^-1 and 0.13 to 2.5 mg·L^-1 for VPHC and between 23.7 to 474 mg·L^-1 for EPHC, with detection limits of 0.003 mg·L^-1 and 0.024 mg·L^-1 for the 2 items respectively. Tests for precision and recovery by standard addition method were performed, giving results of RSDs (n=6) all ≤ 10%, and recovery in the range of 89.0% to 103%.