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
TL;DR: In this paper, a depletion experiment method is suggested that consists of running several SPMEs from the same standard sample with the same conditions and 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.
Abstract: Because 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.
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TL;DR: In this paper, the problem of analyte extraction by poly(dimethylsiloxane) (PDMS) fiber coatings turned out to be mainly attributed to experimental errors when applying conventional static SPME approaches.
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, ...
92 citations
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.
80 citations
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.
67 citations
TL;DR: In this paper, a simple, rapid and accurate method on the basis of solid phase microextraction (SPME) in combination with multicapillary gas chromatography 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.
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).
66 citations
TL;DR: A review of the state of the art in MSPME, including theory and applications, can be found in this article, where the authors also discuss the limits of detection and quantification, and the use of this methodology to determine fiber-sample distribution constant.
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.
61 citations
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TL;DR: In this paper, solid phase microextraction (SPME) and gas chromatography-mass spectroscopy (GC-MS) were used for the determination of residues of insecticides and fungicides commonly used for vineyard protection.
Abstract: The new extraction method, so-called solid-phase microextraction (SPME), coupled with gas chromatography-mass spectroscopy (GC-MS), was examined for the determination of residues of insecticides and fungicides commonly used for vineyard protection Aqueous solutions containing between 0 and 15% ethanol were spiked with 12 selected compounds and diphenylamine at the level of 20 ppb (v/w), extracted onto a silica fiber coated with a 100-μm thickness of poly(dimethylsiloxane), and desorbed in the chromatograph injector The influence of ethanol on the partition equilibrium between the adsorbant and the liquid was studied for each product In several cases, equilibria were obtained, and the extracted amounts of pesticides were shown to be dependent on the nature of the molecule and on the ethanolic content of the solution In contrast, the time necessary to reach these equilibria was the same in the presence and absence of ethanol Additional experiments on natural wines spiked at the same level of concentrat
70 citations
01 Mar 1999-Food Additives and Contaminants Part A-chemistry Analysis Control Exposure & Risk Assessment
TL;DR: The solvent-free SPME procedure was found to be quicker and more cost effective than the solvent extraction methods commonly used and limits of detection, repeatability and linearity for standard calibration in strawberries were obtained.
Abstract: A new solid phase microextraction method for the determination of pesticide residues in strawberries for 16 commonly used compounds was described. The strawberries were crushed and centrifuged. An aliquot of the well agitated aqueous supernatant (4ml) was extracted with a fibre coated with polydimethylsiloxane (PDMS, 100 μm) for 45min at room temperature. Identification and quantification were achieved using a gas chromatography-mass spectrometry (GC-MS) system and selective ion monitoring (SIM). The method was tested for the following pesticides: carbofuran, diethofencarb, penconazole, hexaconazole, metalaxyl, folpet, bromopropylate, dichlofluanid, α-endosulfan, β-endosulfan, parathion ethyl, procymidone, iprodione, vinclozolin, myclobutanil and chlorothalonil. Limits of detection, repeatability and linearity for standard calibration in strawberries were obtained. Positive and negative effects of the matrix between the extracting solution of strawberries and water were observed. Stabilities of these comp...
47 citations
TL;DR: In this paper, the Rapid Solid Phase Micro Extraction (SPME) technique has been used in the analysis of water for pesticide residues in laboratory studies, which is the first time, to the best of our knowledge, that SPME has been applied to water analysis of herbicide residues.
39 citations
TL;DR: In this article, the applicability of solid phase microextraction (SPME) and gas chromatography with seven chlorinated organic compounds was evaluated and the results show that SPME can be a valuable alternative to common preconcentration techniques in the quantification of hydrophobic organics in pure and octanol-saturated water.
Abstract: The critical step in the determination of water solubilitiy (Sw) and octanol-water partition coefficient (Kow) of hydrophobic organic chemicals by using the generator-column technique and the slow-stirring procedure, respectively, is the exact quantification of the low water-phase concentrations of the substances under investigation. We have tested the applicability of solid-phase microextraction (SPME) and gas chromatography with seven chlorinated organic compounds. The substances cover a Sw range from 500 mg/L to 7 ng/L and a log Kow range from 3 to 8. The results show that SPME can be a valuable alternative to common preconcentration techniques in the quantification of hydrophobic organics in pure and octanol-saturated water. The apparent SPME distribution constants KSPME (obtained with the 100 μm-PDMS fiber for analyte’s partitioning between fiber coating and aqueous sample) do not correlate directly with octanol/water partition coefficients and thus cannot be recommended as a surrogate parameter for Kow.
29 citations