BACKGROUNDAs an important index of land environmental quality, the content of petroleum substances determines the use of the land. It also reflects the effect of reclamation and treatment of polluted land to a large extent. The determination methods of petroleum substances in soil samples include gas chromatography, infrared spectrometry, and ultraviolet method. The gas chromatography mainly analyzes saturated alkanes in the samples. The infrared spectrometry identifies the petroleum substances in the samples by measuring the characteristic absorption values under different wave numbers. However, tetrachloroethene used as the solvent is harmful to the environment. Moreover, the pretreatment efficiency is low and the detection limit is high.

OBJECTIVESTo develop a method with high pre-treatment efficiency, low detection limit and good reproducibility.

METHODSPetroleum substances in the reclaimed land samples have low content, most of the components are difficult to volatilize, the structure is complex, and the matrix interference is large. Using n-hexane as the solvent and accelerated solvent extraction (ASE) as the pretreatment method, the petroleum substances in the samples were determined by fluorescence photometer.

RESULTSUsing the petroleum standard material for marine environmental monitoring as the calibration material to prepare a working curve, the linear correlation coefficient was 0.9997, the detection limit was 0.40mg/kg, precision was 1.10% to 8.76% and the recovery was 89.0% to 95.7%. The results of actual samples were consistent with those of the currently valid infrared spectrophotometry method HJ 1051-2019, and the measurement results of high-content samples were higher than those of the infrared method.

CONCLUSIONSThe pretreatment method ASE has high automation and high extraction efficiency. It can be used to increase the precision by 11.5%-67.3%. For samples with a relatively complex structure of petroleum components and that are difficult to extract, the detection limit of this method is lower than that of the infrared method (4mg/kg).