Determination of Petroleum Oil in Soil by Fluorescence Spectrophotometry with Oscillatory Extraction

As an important index of soil environmental quality, the determination of petroleum oil has become one of the must-test items in environmental monitoring. The gravimetric method is not suitable for the purpose of environmental monitoring because it can only be used for the determination of non-volatile substances and has low sensitivity. Gas chromatography is mainly used for the determination of C₁₀-C₄₀ saturated alkanes in samples. The infrared spectrometry used characteristic absorption at different wavenumber to characterize the content of petroleum substances in the samples, but the response of infrared spectrometry to aromatic hydrocarbons is not sensitive.

To establish a simple pre-treatment efficiency, low detection limit and good reproducible method for determination of petroleum oil in soil.

Using n-hexane as the solvent, adsorption column as the extraction method and oscillatory as the pretreatment method, petroleum oil was extracted from soil and determined by fluorescence spectrophotometry.

Under the optimal conditions that with 275nm as the excitation wavelength and 315nm as the emission wavelength, the extraction solvent was n-hexane and the extraction method was adsorption column, the calibration curves of petroleum oil were linear with correlation coefficients 0.999, and the detection limit was 3mg/kg. The relative standard derivations (RSDs) were from 2.5% to 9.2% and the average spiked recoveries were between 80.0% and 110%. Compared with the currently valid infrared spectrometry method (HJ 1051—2019), the results of the two methods were consistent.

The solvent of n-hexane has higher toxicity and stability than tetrachloroethene, and better environmental friendliness. The oscillatory extraction method is simple and easy to operate. The detection limit of this method is lower than that of infrared spectrometry (4mg/kg), and the precision and accuracy of the method is good. This method can be used as a supplement to the existing methods for the detection of petroleum in soil.