Nonexhaustive Cyclodextrin-Based Extraction Technique for the Evaluation of PAH Bioavailability

Abstract

Traditionally, soil extraction techniques have been concerned with the determination of "total" organic contaminant concentrations, following an "exhaustive" extraction. However, in light of the increasing body of knowledge relating to organic contaminant availability and aging, such methods have little relevance to the amount of contaminant that may pose an ecological risk i.e., the "bioavailable" portion. Less exhaustive techniques have therefore been the subject of more recent approaches in the hope that they may access the "labile" or bioavailable pool. The use of an aqueous-based extraction technique utilizing hydroxypropyl-β-cyclodextrin (HPCD) is presented here for the extraction of PAHs from soil. The optimization of the method is described in terms of HPCD concentration, extraction time, and solution buffering. The procedure is then tested and validated for a range of 14 C-labeled PAHs (phenanthrene, pyrene, and benzo[a]pyrene) added at a range of concentrations to a range of soil types. The amounts of soilassociated phenanthrene mineralized by catabolically active microorganisms were correlated with total residual phenanthrene concentrations (r 2 ) 0.889; slope of best fit line ) 0.763; intercept ) -5.662; n ) 24), dichloromethane (DCM)-extractable phenanthrene concentrations (r 2 ) 0.986; slope of best fit line ) 0.648; intercept ) 0.340; n ) 24), butan-1-ol (BuOH)-extractable phenanthrene concentrations (r 2 ) 0.957; slope of best fit line ) 0.614; intercept ) 0.544; n ) 24), and HPCD-extractable phenanthrene concentrations (r 2 ) 0.964; slope of best fit line ) 0.997; intercept ) 0.162; n ) 24). Thus, in this study, the microbially bioavailable concentrations of soil-associated phenanthrene were best predicted using the optimized HPCD extraction technique. In contrast, the DCM Soxhlet extraction and the BuOH shake extraction both overestimated phenanthrene bioavailability by, on average, >60%.

Immobilization of pentachlorophenol in soil using carbonaceous material amendments

“…Liste and Alexander (2002) and Kelsey et al (1997) proposed that butanol extraction was a feasible method for earthworm accumulation and bacterial mineralization prediction. While several studies have shown that butanol is an exhaustive extractant and largely overestimate microbial mineralization (Reid et al, 2000;Northcott and Jones, 2003). The butanol extractable PCP from unamended S1, S2, S3 and F soils was 55.2, 60.6, 37.6, and 50.9% of total PCP in soil, respectively (Fig.…”

“…Harsh extractants, such as DCM, are generally used to quantify the total amount of HOCs in soil by a single extraction (Macleod and Semple, 2003), which overestimate the contaminant fraction available to soil biota (Hatzinger and Alexander, 1995;Reid et al, 2000). In this study, DCM was used as a final sequential extractant after CaCl 2 and n-butanol extractions.…”

Content of potentially bioavailable polycyclic aromatic hydrocarbons in rhizosphere soil in relation to properties of soils

“…In literature, various methods of evaluating potentially bioavailable PAH fractions were described (Kelsey et al, 1997;Cornelissen et al, 1998;Cuypers et al, 2000;Hawthorne and Grabanski, 2000;Reid et al, 2000;Liste and Alexander, 2002). In the study presented here, a method of mild-solvent extraction (MSE) with an application of n-butanol as an solvent was used (Kelsey et al, 1997;Liste and Alexander, 2002).…”

“…In the literature, there are descriptions of the various methods used for the determination of the bioavailable fraction of polycyclic aromatic hydrocarbons. In order to evaluate the content of the bioavailable forms, the following methods have been proposed: supercritical-fluid extraction (SFE) (Loibner et al, 2000;Hawthorne and Grabanski, 2000), the application of passive samplers (tenax, semi-permeable membrane devices, octadecyl-modified silica disks) (Cornelissen et al, 1998;Sijm et al, 2000;Akkanen et al, 2001;Maliszewska-Kordybach and Smreczak, 2003), persulphate oxidation (Cuypers et al, 2000), the multi-column system (Zhao and Voice, 2000), the non-exhaustive cyclodextrin-based extraction technique (Reid et al, 2000) and selective chemical extractants (Kelsey et al, 1997;Liste and Alexander, 2002).…”

Peer Reviewed: Nonextractable Pesticide Residues in Soil

“…Techniques include solid-phase extraction using Tenax resins or XAD-4 (38,39), persulfate oxidation (40), and cyclodextrin extraction (41). All of these techniques have shown strong correlations between the microbially degradable fraction and the fraction available to the chemical extractants.…”