Measuring Picogram per Liter Concentrations of Freely Dissolved Parent and Alkyl PAHs (PAH-34), Using Passive Sampling with Polyoxymethylene

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• 作者：Steven B. Hawthorne ; Michiel T. O. Jonker ; Stephan A. van der Heijden ; Carol B. Grabanski ; Nicholas A. Azzolina ; David J. Miller
• 刊名：Analytical Chemistry
• 出版年：2011
• 出版时间：September 1, 2011
• 年：2011
• 卷：83
• 期：17
• 页码：6754-6761
• 全文大小：846K
• 年卷期：v.83,no.17(September 1, 2011)
• ISSN：1520-6882

文摘

Passive sampling with nondepletive sorbents is receiving increasing interest because of its potential to measure freely dissolved concentrations of hydrophobic organic compounds (HOCs) at very low concentrations, as well as its potential for both laboratory use and field deployment. However, consistent approaches have yet to be developed for the majority of HOCs of environmental and regulatory interest. In the present study, a passive sampling method was developed which allows the freely dissolved concentrations of 18 parent and 16 groups of alkyl polycyclic aromatic hydrocarbons (PAHs) on the U.S. Environmental Protection Agency (USEPA)鈥檚 鈥淧AH-34鈥?target compound list to be measured. Commercially available 76-渭m-thick polyoxymethylene (POM) was placed in sediment/water slurries and exposed for up to 126 days, with 28 days found to be sufficient to obtain equilibrium among the sediment, water, and POM phases for the target 2- to 6-ring PAHs. The POM/water partition coefficients (K_POM) necessary to calculate freely dissolved concentrations for parent PAHs were determined in two separate laboratories (one using pure standards, and the other using coal tar/petroleum-contaminated sediments) and agreed very well. Since the so-called 鈥?6鈥?alkyl PAHs on the PAH-34 list actually include several hundreds of isomers for which no standards exist, sediments impacted by coal tar, or spiked with a coal tar/petroleum nonaqueous phase liquid (NAPL) were also used to measure K_POM values for each alkyl PAH cluster. The log K_POM values ranged from ca. 3.0 to 6.2 for 2- to 6-ring parent PAHs, and correlated well with SPARC octanol/water coefficients (K_OW) (correlation coefficient of r² = 0.986). However, log K_POM values for alkyl PAHs deviated increasingly from SPARC log K_OW values with increasing degree of alkylation. A simple empirical model that incorporates the number of carbon atoms in a PAH gave a better fit to the experimental log K_POM values, and was used to estimate log K_POM for alkyl PAHs that could not be directly measured. Detection limits (as freely dissolved concentrations) ranged from ca. 1 part per trillion (ng/L) for the 2-ring PAH naphthalene, down to <1 pg/L (part per quadrillion) for the 5- and 6-ring PAHs. Sorption isotherms were linear (r² > 0.99) over at least 4 orders of magnitude.