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Journal ArticleDOI

Extracted amounts by solid-phase microextraction: A realistic approach to the partition coefficient K

01 Aug 1999-Journal of Chromatographic Science (Oxford University Press)-Vol. 37, Iss: 8, pp 277-282

AbstractBecause of its numerous advantages, the solventless solid-phase microextraction (SPME) sampling method coupled with an efficient chromatographic technique is used more and more to develop new analytical methods pertaining to organic molecules at low concentration in aqueous solutions, especially in the field of environmental chemistry. In a usual analytical procedure, the amount of analyte extracted by the fiber need not be determined, because the quantitation step of the analysis is mainly achieved using SPME external calibration. For some purposes, however, the determination of the partition coefficient K relative to a particular fiber for a specific analyte (for example) has to be calculated with accuracy. The traditional method consists of determining the response coefficient of the detector used for the analyte through a direct-injection calibration curve made from standard solutions in organic solvents and reporting it with the signal observed for the analytical sample. For the same goal, a depletion experiment method is suggested that consists of running several SPMEs from the same standard sample with the same conditions and then fitting the resulting data into an experimental regression curve, the exponential coefficient of which affords an absorption coefficient characteristic of the fiber/analyte system in a defined work-up. This self-calibrating method is revealed to be much more accurate than the previous one. Four pesticides in water solution were chosen to exemplify this study.

Topics: Matrix (chemical analysis) (63%), Internal standard (63%), Calibration curve (62%), Analyte (60%), Solid-phase microextraction (58%)

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Citations
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Journal ArticleDOI
Abstract: Solid-phase microextraction (SPME) using nonpolar fiber coatings is a very useful method for determining concentrations (more precisely, activities) of environmentally relevant very hydrophobic organic compounds (VHOC: alkanes, PCBs, and PAHs). The issue of adsorption (surface effect) versus absorption (partitioning) is of huge importance for the application of SPME to determine VHOC in environmental samples. Competition effects, which are associated with adsorption processes, would result in concentration-dependent and mixture-dependent responses. The confusion in the literature about the processes responsible for analyte extraction by the poly(dimethylsiloxane) (PDMS) fiber coatings turned out to be mainly attributed to experimental errors when applying conventional static SPME approaches. Determining fiber coating distribution coefficients (Kf) using dynamic systems is more accurate in comparison with static systems because analyte losses in the system (due to the fiber uptake, sorption on the walls, ...

91 citations


Journal ArticleDOI
TL;DR: Fibre coating-water distribution constants (Kfw) of more hydrophobic chemicals were determined with six different solid-phase microextraction fibre types by fibre exposure to agitated large-volume water samples lasting several days, comparable with Kfw values obtained under dynamic conditions.
Abstract: Fibre coating-water distribution constants (Kfw) of more hydrophobic chemicals were determined with six different solid-phase microextraction fibre types (including a polyoctylmethylsiloxane (C8) prototype) by fibre exposure to agitated large-volume water samples lasting several days. The results obtained are comparable with Kfw values obtained under dynamic conditions. Octanol-water partition coefficients (Kow) were measured with the mixture of distributing substances to examine log Kfw-log Kow relationships based on a consistent dataset. Kfw values obtained with liquid polymer fibre coatings correlate reasonably well with the hydrophobicity of the test compounds (with decreasing sensitivity in the following order: 7 microm polydimethylsiloxane (PDMS)>100 microm PDMS>C8>polyacrylate) whereas this is not the case with the PDMS-divinylbenzene (DVB) and Carbowax-DVB fibres, partially porous coatings which provide the highest Kfw values for all substances tested.

78 citations


Journal ArticleDOI
TL;DR: The precision and sensitivity of the developed analytical method allowed the investigation of the fate of PUHs in lakes, their degradation during drinking water treatment and their transport within the North Sea.
Abstract: A procedure is presented which allows the ultratrace level determination of phenylurea herbicides (PUHs) in natural waters. Samples were enriched by solid-phase extraction (SPE) on Carbopack B and alkylated with iodoethane and sodium hydride to yield thermostable products. After derivatization, the aqueous samples were extracted and injected by SPME. The use of iodoethane instead of iodomethane allowed the differentiation between parent compounds and the N-demethylated metabolites. Limits of detection were between 0.3 and 1.0 ng/l for the parent compounds. Standard deviations below 10% were achieved for samples containing more than 4 ng/l in very different matrices including Nanopure water, lake water, and waste water treatment plant (WWTP) effluent. Moreover, the para-hydroxylated metabolite of diuron could be quantified with the same procedure. The presence of further metabolites was assessed qualitatively. Chromatography was stable over a large number of measurements even with dirty samples from WWTP effluent. The precision and sensitivity of the developed analytical method allowed the investigation of the fate of PUHs in lakes, their degradation during drinking water treatment and their transport within the North Sea.

64 citations


Journal ArticleDOI
Abstract: A simple, rapid and accurate method on the basis of solid phase microextraction (SPME) in combination with multicapillary gas chromatography (MCGC) hyphenated to inductively coupled plasma-time-of-flight mass spectrometry (ICP-TOFMS) was developed for simultaneous speciation analysis of 10 organometallic compounds of mercury (including inorganic mercury), tin and lead. Headspace SPME was used for extraction/preconcentration of the species from the sample after derivatization with sodium tetraethylborate and subsequent volatilization. Seven SPME fibers were compared in terms of extraction efficiency. A 65 µm polydimethylsiloxane/divinylbenzene fiber offered the best overall extraction efficiency. Using MCGC separation, a total chromatographic run time below 200 s was obtained. With ICP-TOFMS detection peak widths at half height (FWHM) down to 0.3 s were measured without spectral skew thanks to the simultaneous character of the mass spectrometer. Detection limits well below pg g−1 levels were obtained for trimethyllead (TML), dimethyllead (DML), trimethyltin (TMT), dimethyltin (DMT), monomethyltin (MMT), monobutyltin (MBT), dibutyltin (DBT) and tributyltin (TBT). Somewhat higher detection limits were obtained for methylmercury (MeHg, 1.3 pg g−1) and inorganic mercury (Hg2+, 2.0 pg g−1). For extraction/preconcentration of MeHg and Hg2+ the 75 µm carboxen/polydimethylsiloxane (CAR/PDMS) fiber is a better choice. The analytical precision (RSD, %) for 10 successive injections of a standard mixture containing 100 pg of each species was generally below 5%. Propylmercury (PrHg) was used as the internal standard for MeHg and Hg2+ as well as for lead species determination. The method was validated by the analysis of biological and road dust certified reference materials (CRMs).

63 citations


Journal ArticleDOI
Abstract: Multiple solid-phase microextraction (MSPME) is a stepped procedure suitable for avoiding matrix-effect errors in quantitative analyses of complex matrix samples by SPME. It is based on calculating the amount of analyte corresponding to complete extraction using the peak areas of a few consecutive extractions from the same sample. This article reviews the state of the art in MSPME, including theory and applications. It also includes a debate on calculating the limits of detection and quantification, and the use of this methodology to determine fiber-sample distribution constant.

58 citations


References
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Book
01 Jan 1997
TL;DR: The inventor of the technique, Janusz Pawliszyn, describes the theoretical and practical aspects of this new technology, which received an "RD" rating.
Abstract: Solid Phase Microextraction: Theory and Practice Janusz Pawliszyn Solid phase microextraction (SPME) is a recently proposed solvent-free sampling and sample preparation technique. SPME represents a quick, sensitive, and economical approach that can be adopted for field work and can be easily integrated with present analytical instrumentation into an automation process. Written by the inventor of the technique, Solid Phase Microextraction: Theory and Practice describes the theoretical and practical aspects of this new technology, which received an "RD* Experiments for beginners;* A summary of the practical applications of SPME in environmental, food, pharmaceutical, and forensic settings;* Material suitable for SPME courses or self-guided study.

1,938 citations


Journal ArticleDOI
Abstract: The solid-phase microextraction (SPME) technique involves exposing a fused silica fiber that has been coated with a stationary phase to and aqueous solution containing organic contaminants. The analytes partition into the stationary phase until an equilibrium has been reached, after which the fiber is removed from the solution and the analytes are thermally desorbed in the injector of a gas chromatograph

592 citations


Journal ArticleDOI
TL;DR: Solid-phase microextraction was investigated as a solvent-free alternative method for the extraction and analysis of nonpolar semivolatile analytes and eliminates the loss of analytes through adsorption onto container walls and saves transport costs.
Abstract: Solid-phase microextraction (SPME) was investigated as a solvent-free alternative method for the extraction and analysis of nonpolar semivolatile analytes. Analytes were extracted into a polymeric phase immobilized onto a fusedsilica fiber. The fiber was then inserted directly into the injector of a gas chromatograph, and the analytes were thermally desorbed. This new technique allows sampling directly from the source (lake, drinking fountain, etc.) and, therefore, eliminates the loss of analytes through adsorption onto container walls and saves transport costs

357 citations


Journal ArticleDOI
Abstract: Solid phase microextraction (SPME) is a convenient and efficient extraction method that involves using a thin polymer film coating on a fine silica fiber to adsorb analytes of interests from a sample matrix. A theoretical model is proposed to deal with the dynamic adsorption process of SPME. In this model, mass diffusion from the matrix to the SPME polymer film is considered as the rate-determining step in reaching an adsorption equilibrium, and a steady-state diffusion is assumed for SPME in an effectively agitated sampling medium. Mathematical treatment of the adsorption process generates an expression that can describe experimental adsorption time profiles of the SPME process. The expression also provides a directly proportional relationship between the amount of analyte adsorbed by the SPME fiber and its initial concentration in the sample matrix. This relationship indicates that SPME quantification is feasible before an adsorption equilibrium is reached, once the agitation condition and the sampling ...

344 citations


Journal ArticleDOI
Abstract: rn Solid-phase microextraction (SPME) is applied to the analysis of benzene, toluene, ethyl benzene, and xylenes in groundwater. The inexpensive SPME method reduced the sample preparation time by 3-7-fold when compared to purge and trap methods. The relative standard deviation ranged from 3 to 5% for the single-operator relative standard deviation using a methyl silicone fiber. Limits of detection of 1-3 ppb (w/v) were obtained when using a fiber coated with 56-pm methyl silicone film and FID detection. The linear range extended from 15 to 3000 ppb (w/v). Solvents have been completely removed from the sample preparation step.

256 citations