Effect of Pretreatment Process on Loss of Low Cyclic Polycyclic Aromatic Hydrocarbons in Soil Detection by High Performance Liquid Chromatography

To reduce the loss caused by the pretreatment process in the determination of six 2-3 ring polycyclic aromatic hydrocarbons (naphthalene, acenaphthene, acenaphthene, fluorene, phenanthrene, and anthracene) and their substitute, decafluorobiphenyl, in soil sample by high performance liquid chromatography, the pretreatment conditions were optimized and effects of extraction, concentration, purification on the recovery of the 7 targets were explored. After automatically accelerating solvent extraction of the soil sample by the mixed solution consisting of acetone and n-hexane at volume ratio of 1:1, the extract was reduced to 5.0 mL under conditions of vacuum pressure of 0.06-0.07 MPa and temperature of 30℃, and further concentrated to about 1.0 mL under conditions of nitrogen pressure of 100 kPa and temperature of 30℃. If the sample needed to be purified, the above concentrated solution was directly passed through the activated Supelco magnesium silicate solid phase extraction column, and targets was eluted by the mixed solution composed of dichloromethane and n-hexane at volume ratio of 1:1. The targets in the eluent (concentration solution when purification was not requided) was displaced into acetonitrile, and the solution was diluted to 1.0 mL by acetonitrile. Targets in which were separated by SUPELCO LC-PAH chromatographic column, detected by a diode array detector and a fluorescence detector in series, and quantified by external standard method. It was shown that the segmented concentration method mentioned above could effectively reduce the loss of the targets. By analyzing the segmented simulated solutions in the pretreatment process, it was found that the extraction, purification, and nitrogen blowing concentration processes had a relatively small effect on the recovery of the 7 targets, while the vacuum concentration process had a significant effect. Linear relationships between values of the mass concentration and the peak area were kept in the ranges of 0.20-10.0 mg·L^-1 (decafluorobiphenyl) and 0.04-2.00 mg·L^-1 (the 6 targets), respectively. Detection limits (3.143s) were found in the range of 0.2-2.0 μg·kg^-1. The proposed method was used for analysis of the standard sample, and the determined values were within the uncertainty ranges of the identified values, with RSDs (n=5) of the determined values in the range of 1.4%-5.7%.