Sample preparation of soils and bottom sediments for gas chromatography–mass spectrometry determination of PAHS

Polycyclic aromatic hydrocarbons (PAHs) are a class of compounds which have been known to be carcinogenic, teratogenic and mutagenic as well as act as pollutants of environmental objects. The determination of PAHs in complex matrices is difficult, and it is very important to use an efficient sample pretreatment technique. A sample preparation technique was developed involving extractive freezing-out and centrifugation of the samples for the determination of polycyclic aromatic hydrocarbons (PAHs) in soils and bottom sediments using gas chromatography – mass spectrometry (GC–MS). Sochi soils (The Imereti Lowlands), turf, sea bottom sediments (Azov Sea, The Temryuk Bay), river bottom sediment (Kurchansky estuary) and Caio Romano (Cuba) island sand were selected as the objects for the research. Soils and bottom sediments which contained no determined PAHs were used as model samples. The conditions of sample preparation have been optimized, and the extraction effects of acetonitrile with water on the PAHs recoveries have been investigated. It was found that for the determination of the compounds consisting from two to four fused aromatic rings such as naphthalene, 2-methylnaphthalene, acenaphthylene, biphenyl, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene and pyrene, the extraction occurred when the extractive mixture contained 15% acetonitrile. The proposed method detection limits of individual compounds ranged from 0.83 to 0.92 µg/kg. The extractive mixture containing 50% acetonitrile was proposed for the determination of 20 PAHs such as naphthalene, 2-methylnaphthalene, acenaphthene, biphenyl, acenaphthylene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benz[a]anthracene, chrysene, triphenylene, benz[b]fluoranthene, benz[k]fluoranthene, benz[e]pyrene, benz[a]pyrene, indene[1,2,3–c,d]pyrene, dibenz[a,h]anthracene, benz[g,h,i]perylene. The extraction of PAHs in these conditions demonstrated the recoveries from 61% to 97%. As matter of fact, the lower recoveries of PAHs, that contained four or more fused aromatic rings, have been caused by the sorption in the cracks of the solid aqueous phase. The extraction, clear-up of extract and concentration were realized as one step of the sample pretreatment. As a result, the rapid and express technique of the sample preparation with combined GC-MS were proposed for the PAHs determination in soils and bottom sediments. This method’s limits of individual PAHs quantitation ranged from 1 to 5 µg/kg, and these were lower that the maximum permissible concentration.