Determination of Petroleum Hydrocarbons (C₁₀—C₄₀) in Soil by Gas Chromatography with Pressurized Fluid Extraction and Magnesium Silicate Column Purification

An aliquot (10.0 g) of the soil sample was taken, and 10 g of diatomite was added. After mixing, dehydration and grinding, the mixture was treated by pressurized fluid extraction. Static extraction was performed twice with the mixed solution of n-hexane and acetone at volume ratio of 1∶1 as extractant at temperature of 100 ℃, pressure of 11.70 MPa, and extraction time of 5 min. The extract was concentrated, and passed through the activated magnesium silicate purification column, and the effluent was collected. The concentration device was washed by 7 mL of the mixed solution of n-hexane and acetone at volume ratio of 9∶1, and the washing solution was passed through the activated magnesium silicate purification column. The effluent was combined and concentrated, and the resulting solution was introduced into the gas chromatograph. Petroleum hydrocarbons (C₁₀-C₄₀) in the sample were separated by the heating program on the HP-5MS chromatographic column. It was shown that linear relationship between values of the mass concentration and peak area of petroleum hydrocarbons (C₁₀-C₄₀) was kept in the range of 248-9 300 mg · L⁻¹, with detection limit (3. 143s) of 2. 4 mg · kg⁻¹. The spiked recoveries were in the range of 93. 5%-103%, and the determined values of petroleum hydrocarbons (C₁₀-C₄₀) in soil quality control samples were within the certified value range, with RSDs (n=6) of the determined values in the range of 7.1%-8.8%.