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Solid-phase microextraction (SPME) has often been used to estimate the freely dissolved concentration ( Cfree) of organic contaminants in sediments. A significant limitation in the application of SPME for Cfree measurement is the requirement for attaining equilibrium partition, which is often difficult for strongly hydrophobic compounds such as DDT. A method was developed using SPME with stable isotope-labeled analogues as performance reference compounds (PRCs) to measure Cfree of DDT and metabolites (DDTs) in marine sediments. Six 13C-labeled or deuterated PRCs were impregnated into polydimethylsiloxane (PDMS) fiber before use. Desorption of PRCs from PDMS fibers and absorption of DDTs from sediment were isotropic in a range of sediments evaluated ex situ under well-mixed conditions. When applied to a historically contaminated marine sediment from a Superfund site, the PRC-SPME method yielded Cfree values identical to those found by using a conventional equilibrium SPME approach (Eq-SPME), wherease the time for mixing was reduced from 9 d to only 9 h. The PRC-SPME method was further evaluated against bioaccumulation of DDTs by Neanthes arenaceodentata in the contaminated sediment with or without amendment of activated carbon or sand. Strong correlations were consistently found between the derived equilibrium concentrations on the fiber and lipid-normalized tissue residues for DDTs in the worms. Results from the present study clearly demonstrated the feasibility of coupling PRCs with SPME sampling to greatly shorten sampling time, thus affording much improved flexibility in the use of SPME for bioavailability evaluation. Environ Toxicol Chem 2013;32:1946-1953. © 2013 SETAC [ABSTRACT FROM AUTHOR]

A passive water sampler with low-density polyethylene (LDPE) as the sorbent phase was built and field-tested for sensing freely dissolved concentrations of hydrophobic organic compounds (HOCs) in fresh and coastal water. Based on the measured LDPE-water partition coefficients ( Kpew) of 12 polycyclic aromatic hydrocarbons (PAHs) and dichlorodiphenyltrichloroethane (DDT) and its seven metabolites, the detection limits with the passive sampler containing 10-g LDPE ranged from 0.04 to 56.9 pg/L in the equilibrium sampling mode. Furthermore, the utility of the passive sampler in measuring dissolved HOC concentrations in open waters was examined through a comparison with solid-phase extraction combined with liquid-liquid extraction (SPE-LLE) and poly(dimethyl)siloxane (PDMS) coated fiber samplers. The total concentrations of PAHs (3.8-16 ng/L) obtained by the passive sampler were lower than those (87.7-115.5 ng/L) obtained through SPE-LLE. This large difference was probably attributable to slower water exchange in and out of the passive sampler as time progressed because of blockage by algae in eutrophia reservoirs and high dissolved organic carbon contents resulting in higher-than-expected PAH concentrations by SPE-LLE. Furthermore, the concentrations and compositional profiles of DDXs (sum of p,p′-DDT, p,p′-DDD, p,p′-DDE, o,p′-DDT, o,p′-DDD, o,p′-DDE, and p,p′-DDMU) at site A obtained by the passive sampler agreed with the results obtained with the PDMS-coated fibers, suggesting that the passive sampler was able to reasonably quantify dissolved HOCs in seawater. Environ. Toxicol. Chem. 2012; 31: 1012-1018. © 2012 SETAC [ABSTRACT FROM AUTHOR]