Modified silica sorbent for efficient matrix cleanup of lipophilic interferences in the analysis of polycyclic aromatic hydrocarbons

In the chromatographic determination of PAHs in samples of bottom sediments, impurities of aliphatic compounds ( n -alkanes, resins, etc.) course a significant interfering effect. For preliminary purification of the samples, it is proposed to use a sorbent based on amorphous silicon dioxide, synthesized by sulfuric acid decomposition of natural aluminosilicate raw material — nepheline concentrate. The silica surface was modified with formation of a ligand layer based on stearic acid, which increased the selectivity of the resulting sorbent towards lipophilic impurities. To confirm the effectiveness of the proposed sorbent as an alternative sample preparation technique, solid-phase extraction using the QuEChERs method was used: a significant reduction in the influence of impurities on the results of PAHs determination by HPLC after purification was established. To quantitatively assess the sorbent’s effectiveness, extracts from a bottom sediment sample were analyzed by GC-MS after adding a standard mixture of 16 PAHs. It has been experimentally demonstrated that the proposed sorbent effectively removes matrix impurities: for PAHs with a high molecular weight containing three or more aromatic rings, the recovery is 1.2 – 2 times higher than the results obtained after purification using the QuEChERs method, reaching 82 – 97%. For «light» PAHs (naphthalene, fluorene), losses of analytes of up to 40 – 50% are observed due to sorption in mesopores; artifacts of extract contamination with acenaphthene and phenanthrene from the cartridge housing and filter material have also been identified (to eliminate them, it is necessary to use inert housings and fiberglass membranes). Despite the identified limitations, the proposed sorbent is a promising material for purifying extracts from lipophilic impurities when determining PAHs for environmental monitoring purposes.