Potential of ethyl acetate in the determination of extractable organic halogens (EOX) from contaminated soil, sediment, and sewage sludge

The potential of methyl-tert. butyl ether, toluene and ethyl acetate for determining extractable organic halogens (EOX) from contaminated soil, lake sediments and sewage sludge was investigated and compared with hexane, which is prescribed in the German standard method of EOX determination. Soxhlet-extraction with ethyl acetate proved most efficient and yielded 2 - 6 times the EOX-values obtained by hexane. Washing of ethyl acetate extracts is not necessary, since interferences by coextracted inorganic halides was negligible if dried samples are extracted. The detection limit is in the range of 0.1 - 0.2 μg g−1 with standard deviations between 3 - 7%. The method was further evaluated by application onto soil samples spiked with 3-chloro-4-hydroxy-phenylacetic acid (1) and phosphoric acid-tris-(2-chloroethyl) ester (II). Ethyl acetate recoveries were 45 - 52 % for I and 77 - 110% for II, compared with 6 - 13 % recovery by hexane. Ethyl acetate extraction substantially improves the EOX-determination but it might still underestimate the true value. For all sewage sludge, soil and sediment samples the EOX/EOM ratio did also increase by the use of ethyl acetate. This indicates the importance of polar halogenated contaminants which are amenable by ethyl acetate extraction rather than by hexane. The implications of EOX/EOM ratios for EOX dynamics are discussed.