Theoretical Considerations on the Use of Solid-Phase Microextraction with Complex Environmental Samples

Southern California Coastal Water Research Project, Westminster 92683, USA.
Environmental Science and Technology (Impact Factor: 5.33). 09/2002; 36(15):3385-92. DOI: 10.1021/es025653p
Source: PubMed

ABSTRACT The equations governing the use of equilibrium solid-phase microextraction (SPME) for environmental samples with complex heterogeneous matrices were derived in terms of parameters commonly measured or estimated by environmental scientists. Parameterization of the SPME equations allowed for the a priori prediction of SPME performance as a function of analyte and sample properties as well as experimental conditions. A theoretical evaluation of SPME was performed for a broad range of realistic scenarios using calculated equilibrium partitioning parameters and the implications for practical applications were discussed. Potential pitfalls and errors in quantitative measurements were identified, and different approaches to SPME calibration were presented. The concept of an optimum minimum volume for the analysis of heterogeneous environmental samples was presented and fully developed. Data from three previous studies were used to validate the correctness of our theoretical framework; the agreement between the measured relative recoveries of a variety of hydrophobic organic chemicals and theoretical predictions was reasonable. The results of this study highlight the potential for SPME to be a valuable technique for the measurement of hydrophobic organic contaminants in complex environmental samples. The SPME technique appears to be especially well suited for samples with high solids-to-water ratios and/or large sample volumes. Examples of such applications include sediment interstitial water and in situ field measurements, respectively.

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Available from: James A Noblet, May 07, 2014
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    • "This was achieved by keeping the phase ratio between water and polymer well above the polymer to water partition coefficient. For equilibrium sampling in sediment, it is often acceptable to temporarily deplete the aqueous concentration and then to use the sediment matrix as a partitioning donor to buffer the chemical activity during the sampling (Mayer et al. 2000; Zeng and Noblet 2002; Reichenberg and Mayer 2006). However, it is then necessary to ensure that only a small fraction of the sorbed analyte is released from the matrix, to avoid desorption resistance in confounding the equilibrium sampling measurement. "
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    ABSTRACT: Passive sampling methods (PSMs) allow the quantification of the freely dissolved concentration (Cfree ) of an organic contaminant even in complex matrices such as sediments. Cfree is directly related to a contaminant's chemical activity, which drives spontaneous processes including diffusive uptake into benthic organisms and exchange with the overlying water column. Consequently, Cfree provides a more relevant dose metric than total sediment concentration. Recent developments in PSMs have significantly improved our ability to reliably measure even very low levels of Cfree . Application of PSMs in sediments is preferably conducted in the equilibrium regime, where freely dissolved concentrations in the sediment are well linked to the measured concentration in the sampler via analyte-specific partition ratios. The equilibrium condition can then be assured by measuring a time series or a single time point using passive samplers with different surface to volume ratios. Sampling in the kinetic regime is also possible and generally involves the application of performance references compounds for the calibration. Based on previous research on hydrophobic organic contaminants, it is concluded that Cfree allows a direct assessment of (1) contaminant exchange and equilibrium status between sediment and overlying water, (2) benthic bioaccumulation and (3) potential toxicity to benthic organisms. Thus, the use of PSMs to measure Cfree provides an improved basis for the mechanistic understanding of fate and transport processes in sediments and has the potential to significantly improve risk assessment and management of contaminated sediments. Integr Environ Assess Manag © 2013 SETAC.
    Integrated Environmental Assessment and Management 04/2014; 10(2):197-209. DOI:10.1002/ieam.1508 · 1.38 Impact Factor
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    • "More than two decades ago, solid phase microextraction (SPME) was introduced by Arthur and Pawliszyn [1] as a new, solvent-free extraction technique. Since that time, SPME has evolved into a widely used alternative to traditional extraction methods of organic compounds, and has been applied in various research areas, from environmental chemistry [2] [3] to biomedical analysis. [4] [5] [6] [7] The interpretation of the extraction step is the most straightforward if SPME is applied under non-depletive conditions (nd-SPME). "
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    ABSTRACT: Environmental context. Organic hydrophobic compounds are present in water in low concentrations, and they can be analysed by means of a preconcentration technique called solid phase microextraction. We investigate the role of sorbing nanoparticles in the solid phase microextraction analysis of organic compounds. Our results show that nanoparticles are capable of partitioning between water and the solid phase and aggregate at the interface leading, most probably, to substantial overestimation of the original sample concentration. Abstract. Solid phase microextraction (SPME) is commonly used to measure the free concentration of fairly hydrophobic substances in aqueous media on the basis of their partitioning between sample solution and a solid phase. Here we study the role of nanoparticles that may sorb the analyte in the sample medium. As an example case, the solid phase poly(dimethylsiloxane) (PDMS) is exposed to an aqueous dispersion containing silica nanoparticles with 10-nm radius. Confocal laser microscopic data show that these SiO 2 nanoparticles do enter the PDMS and partition between the sample solution and solid phase. Moreover, they form aggregates at the surface of the solid phase. The overall partitioning of the SiO 2 nanoparticles in the aqueous sample–PDMS system is examined and potential effects on the SPME analysis of organic analytes are indicated. Additional keyword: nanoparticulate species.
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    • "Results might indicate much lower or higher levels than the true average because of the timing of significant concentration fluctuations during the monitoring period (Woolfenden, 2010). Additionally, the sensitivity for very volatile compounds may be compromised as a result of the low volume of the sorbent layer (less than 1 μL) on the support (Zeng and Noblet, 2002). The fragility of the fused-silica fiber necessitates careful handling during use and limits the lifetime of the SPME fiber. "
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    ABSTRACT: Volatile organic compounds (VOC) are the total organic compounds that contribute to photochemical ozone formation. They have a vapor pressure greater than 0.013 kPa at 298 K (according to the American Society for Testing and Materials (1996)), 0.01 kPa at 293 K (according to the European Union (1999)), or 10 Pa at 298 K (according to the U.S. Environmental Protection Agency (1999)), with a lower boiling point limit of 50–100°C and an upper boiling point limit of 240–260°C. VOC include countless potentially hazardous substances released to the outdoor or indoor environment. The prevention or reduction of exposure to VOC in the air requires qualitative and quantitative analysis of these chemical agents. A correct assessment of human exposure to VOC requires appropriate and efficient methods of sampling and analysis. The authors present a survey of VOC definitions, an analytical discussion of the necessity and viability of exposure studies, the principal VOC studied, and a critical revision of methods of sampling and analyses.
    Critical Reviews in Environmental Science and Technology 01/2013; 43(1). DOI:10.1080/10643389.2011.604239 · 3.47 Impact Factor
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