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
References
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TL;DR: In this paper, solid phase microextraction coupled with GC-MS (electron impact ionization and negative chemical ionization) was used to determine chlorophenols in landfill leaches and soil.
109 citations
01 Jan 1998
TL;DR: In this article, solid phase microextraction coupled with GC-MS (electron impact ionization and negative chemical ionization) was used to determine chlorophenols in landfill leaches and soil.
Abstract: Abstract This work evaluates solid-phase microextraction coupled with GC–MS (electron impact ionization and negative chemical ionization) to determine chlorophenols in landfill leaches and soil. A polyacrylate coated fiber is used to investigate the optimal experimental procedures, which include adsorption time, pH, salt effect, desorption time, temperature and the depth of the fiber in the injector. Detection limits are determined to be in low ng/l range and better than those obtained by US Environmental Protection Agency methods using a conventional extraction technique for chlorophenols in water. According to the analytical validations, the linearity of the absorption ranges from 0.1–100 μg/l with R.S.D.s below 9%. In addition, the feasibility of applying the proposed method to determine chlorophenols in real samples is examined by analyzing landfill leachate samples and soil samples contaminated with pentachlorophenol. All the studied chlorophenols are determined in the soil contaminated samples. Moreover, the pentachlorophenol detected in the landfill leachate is estimated in the level of 21.6 μg/l with an internal standard method. The quantities of the other studied chlorophenols are at the level of 0.1 μg/l. The effects of humic acids and a surfactant on the extraction of chlorophenols in the landfill leachate have been studied.
103 citations
TL;DR: In this article, the SPME-GC method was used to investigate the mobility of hexachlorocyclohexanes (HCHs) in wetland soils near Bitterfeld.
92 citations
TL;DR: In this paper, the effect of headspace capacity on SPME extraction results and kinetics was illustrated on an example of amphetamine and methamphetamine determination in water, and a dramatic improvement in extraction speed was achieved by increasing the extraction temperature, and thus also the headspace-sample partition coefficients.
Abstract: The sample volume plays a very important role in solid phase microextraction (SPME) analysis. Its effect on the results of analysis can be neglected only when it is much larger than the fibre capacity KVf (K = fibre/sample partition coefficient, Vf = fibre volume). Good agreement was obtained between theoretical predictions and experimental results for analyte extraction from two- and three-phase systems. The effect of headspace capacity on SPME extraction results and kinetics was illustrated on an example of amphetamine and methamphetamine determination in water. A dramatic improvement in extraction speed was achieved by increasing the extraction temperature, and thus also the headspace–sample partition coefficients. Difficulties with the accurate determination of large partition coefficients are discussed on an example of the extraction of C8–C12 hydrocarbons from air. Analyte sorption on the container walls led to significant losses of less volatile compounds, especially when vials of large surface-to-volume ratio were used. A discussion of problems encountered when trying to determine accurately partition coefficients of semi-volatile compounds in water is also presented.
87 citations
TL;DR: The solid phase micro extraction technique (SPME) using a polyacrylate coated fiber has been examined with the aim to determine phenolic components in strong contaminated waste water as discussed by the authors.
Abstract: The solid-phase micro extraction technique (SPME) using a polyacrylate coated fibre has been examined with the aim to determine phenolic components in strong contaminated waste water. Considering the high contents and the great variety of accompanying organic material, the feasibility of SPME-GC-MS analysis has been tested. In this connection the influence of matrix components on the SPME results are discussed. EPA-604 phenols and some other phenolic components have been sampled by a polar fibre under standard conditions and in original waste water. The effects of defined concentrations of humic acids and surfactants on the recovery of phenols have been studied. The influence of other organics, e.g. hexachlorocyclohexane isomers, on the recoveries of phenols are discussed. Finally, a comparison between results of a liquid-liquid extraction and SPME describes the performance of SPME regarding the phenol analysis of strong-loaded water.
86 citations