Solid-phase microextraction effect

Majcenovic, A. B., Schneider, R., Lepoutre, J.-P., Lempereur, V., and Baumes, R. (2002). Synthesis and stable isotope dilution assay of ethanethiol and diethyl disulfide in wine using solid phase microextraction. Effect of aging on their levels in wine. /. Agric. Food Ghem. 50, 6653-6658. 

A recent method, still in development, for determining total 4-nitrophenol in the urine of persons exposed to methyl parathion is based on solid phase microextraction (SPME) and GC/MS previously, the method has been used in the analysis of food and environmental samples (Guidotti et al. 1999). The method uses a solid phase microextraction fiber, is inserted into the urine sample that has been hydrolyzed with HCl at 50° C prior to mixing with distilled water and NaCl and then stirred (1,000 rpm). The fiber is left in the liquid for 30 minutes until a partitioning equilibrium is achieved, and then placed into the GC injector port to desorb. The method shows promise for use in determining exposures at low doses, as it is very sensitive. There is a need for additional development of this method, as the measurement of acetylcholinesterase, the enzyme inhibited by exposure to organophosphates such as methyl parathion, is not an effective indicator of low-dose exposures. 

Principles and Characteristics As mentioned already (Section 3.5.2) solid-phase microextraction involves the use of a micro-fibre which is exposed to the analyte(s) for a prespecified time. GC-MS is an ideal detector after SPME extraction/injection for both qualitative and quantitative analysis. For SPME-GC analysis, the fibre is forced into the chromatography capillary injector, where the entire extraction is desorbed. A high linear flow-rate of the carrier gas along the fibre is essential to ensure complete desorption of the analytes. Because no solvent is injected, and the analytes are rapidly desorbed on to the column, minimum detection limits are improved and resolution is maintained. Online coupling of conventional fibre-based SPME coupled with GC is now becoming routine. Automated SPME takes the sample directly from bottle to gas chromatograph. Split/splitless, on-column and PTV injection are compatible with SPME. SPME can also be used very effectively for sample introduction to fast GC systems, provided that a dedicated injector is used for this purpose [69,70],... 

Solid-phase microextraction (SPME) is effectively a miniamrised version of SPE. Instead of using a packed cartridge, a rod is typically used, which is coated with the stationary phase. This is dipped into a solution of the analyte and allowed to extract for a pre-determined period of time. After this incubation period, the rod is removed from the solution and may be inserted directly into the injection system of the GC or HPLC. All of these operations can be automated on an autosampler. Clearly, the success of this technique depends intimately on the affinity of the analyte for the stationary phase. Frost, Hussain and Raghani [34] used SPME with GC-FID to measure benzyl chloride and chloroethylmethyl ether (amongst other process impurities) in pharmaceutical preparations. 

Arthur and Pawliszyn introduced solid-phase microextraction (SPME) in 1990 as a solvent-free sampling technique that reduces the steps of extraction, cleanup, and concentration to a unique step. SPME utilizes a small segment of fused-silica fiber coated with a polymeric phase to extract the analytes from the sample and to introduce them into a chromatographic system. Initially, SPME was used to analyze pollutants in water - via direct extraction. Subsequently, SPME was applied to more complex matrixes, such as solid samples or biological fluids. With these types of samples, direct SPME is not recommended nevertheless, the headspace mode (HSSPME) is an effective alternative to extracting volatile and semivolatile compounds from complex matrixes. (Adapted from Llompart et ah, 2001)... 

The use of headspace solid-phase microextraction (HS-SPME) combined with GC was effective for isolation and determination of alkylpyrazines in cocoa liquor <2004JBS267, 2004MI291>, and similarly methoxypyrazine in wine was analyzed by HS-SPME/2-D GC <2005MI1075>. 

Deibler, K.D. 2001. Measuring the effects of food composition on flavor release using the retronasal aroma simulator and solid phase microextraction. Ph.D. dissertation, pp. 131. Cornell University, Ithaca, New York. 

James and Stack [131] found that solid-phase microextraction is an effective technique for determining volatile organic compounds in landfill sites. The headspace above the sample was sampled. 

Wennrich [167] optimised important accelerated solvent extraction parameters, such as extraction temperature and time, using a spiked wetland soil. The effect of small amounts of organic modifiers on the extraction yields was studied. An extraction temperature of 125 °C and ten-minute extractions performed three times proved optimal. Two accelerated solvent extraction-solid-phase microextraction procedures without and with an organic modifier (5% acetonitrile) were evaluated with respect to precision and detection limits. 

An effective combination of focused microwave-assisted extraction with solid-phase microextraction (FMAE-SPME) was carried out for the extraction of cocaine... 

Chapman, D.M., Thomgate, J.H., Matthews, M.A., Guinard, J.X., and Ebeler, S.E. (2004). Yield effects on 2-methoxy-3-isobutylpyrazine concentration in Cabernet Sauvignon using a solid phase microextraction gas chromatography/mass spectrometry method. J. Agric. Food Chem., 52, 5431-5435. 

Calibration is carried out using standard calibration curves. The simplicity, repeatability, and low cost of the method have allowed its use for routine determination of trihalomethanes in tap water. SOME has also been compared with solid phase microextraction (SPME), purge and trap (P T), and direct aqueous injection (DAI) [10]. This technique offers accuracy comparable with that obtained using P T and DAI. With respect to conventional LEE, the SDME method is more accurate. In contrast to DAI and P T, it requires no special equipment. SDME has been used for extraction of chlorophenols [II], pesticides [12, 13], warfare agents [14], and butanone derivatives [15], and for control of food products [16]. The low costs of the SDME method (typical GC syringe and 2-3 pL of solvent), simplicity, and short extraction time (approximately 15 min) make it particularly suitable for preliminary analyses of organic pollutants in water samples. It can also be an effective alternative to SPME, as it does not require the use of expensive instrumentation. 

Several analytical approaches are employed to quantify sulphur volatiles in wine among them, the headspace procedure, such as the Purge and Trap, and solid-phase microextraction methods, combined with GC coupled to different detectors, was shown to be quite effective (Mestres et al., 2000 Rauhut et al., 1998). Recent papers suggest that the HS-SPME technique, with an improved choice of fiber coating phases, would be one of the more promising approaches for the concurrent measurement of compounds with different boiling points (Mestres et al., 2002 Fang and Qian, 2005). 

Figure 5.12 Temperature effect in the HS-SPME adsorption of the wine CFSV on DVB/CAR/PDMS fiber. (Reprinted from Rapid Communications in Mass Spectrometry 21, Fedrizzi et al., Concurrent quantification of light and heavy sulphur volatiles in wine by headspace solid-phase microextraction coupled with gas chro-matography/mass spectrometry, p. 711, Copyright 2007, with permission from John Wiley Sons, Ltd)...

Solid-phase microextraction is controlled by diffusion rates and partition effects. In typical quantitative analyses, for this technique to be reproducible, the extraction process should continue until the partitioning events reach equilibrium and all variables affecting the partitioning must be controlled. For a two-phase system, the extraction is dependent on the analyte s partition coefficient and the volumes of the solid phase and the water. In the headspace technique, equilibrium must be reached between all three phases the water, the vapor, and the solid phase. 

Quantification of aroma-impact components by isotope dilution assays (IDA) was introduced in food flavor research by Schieberle and Grosch (1987), when trying to take into account losses of analytes due to isolation procedures. The labeled compounds have to be synthesized, the suitable fragments have to be chosen, and calibration has to be effected. A quantitative determination of ppb levels of 3-damascenone (Section 5,D.38) in foods, particularly in roasted coffee (powder and brew), was developed by Sen et al. (1991a). Semmelroch et al. (1995) quantified the potent odorants in roasted coffee by IDA. Hawthorne et al. (1992) directly determined caffeine concentration in coffee beverages with reproducibility of about 5 % using solid-phase microextraction combined with IDA. Blank et al. (1999) applied this combined method to potent coffee odorants and found it to be a rapid and accurate quantification method. They also concluded that the efficiency of IDA could be improved by optimizing the MS conditions. 

Eisert R. and Pawliszyn J. (1997) New trends in solid-phase microextraction. Crit. Rev. Anal. Chem. 27, 103 35. Elmore J.S. and Nursten H.E. (1990) A comparison of the headspace extracts of instant and ground coffee. In Flavour Science and Technology Bessiere Y, and Thomas A.F. Eds, John Wiley Sons, New York, pp. 203-4. Elmore J.S. and Nursten H.E. (1993) The effect of 2-furanmethanethiol upon the flavour of instant coffee. Int. J. Food Sci. Technol. 28, 531 6. 

Dugay, J., Miege, C., and Hennion, M. C., Effect of the various parameters governing solid-phase microextraction for the trace-determination of pesticides in water, J. Chromatogr. A, 795, 27-42, 1998. 

Before applying solid-phase microextraction to the water extracts obtained from hot water extraction of rosemary, optimization of experiments were conducted to determine the optimum working conditions for SPME, including water volume, SPME time, and carry over effect. Polydimethylsiloxane fiber (PDMS, 100 tun, Supelco, Bellefonte, PA) was used for performing solid-phase microextraction. 

Three different extraction volumes (2,4, and 8 mL) were tested with SPME extraction time set to IS min. The solid-phase microextraction time studied was IS, 30, and 60 min viiile die water volume was set to 4 mL. In order to study the fiber carryover effect in GC analysis, the total thermal desorption time (at 250 °C) was set to 10 min. Two sets of experiments were performed 1-min thermal desorption followed by 9-min desorption, and S-min desorption followed by S-min desotptioa... 

Used as preservatives in many topical pharmaceutical products, paraben esters have been found to exhibit estrogenic effects that have been linked to breast cancer. This has led to requiranents for their rapid and quantitative detection. Traditional methods of analysis are slow and tedious. For gas chromatographic methods, derivatization as silyl- or fluoroacetyl derivatives followed by extraction and sample cleanup complicate the process, while liquid chromatographic methods require extraction and long chromatographic run times. To increase speed and decrease complexity, solid phase microextraction with ion mobility spectrometry (SPME-IMS) was used for the determination of parabens in pharmaceutical formulations. ... 

Liu, M. Zeng, Z. Xian, Y. (2005). Elimination of matrix effects for headspace solid-phase microextraction of important volatile compounds in red wine using a novel coating. Analytica Chimica Acta 540, 341-353... 

Dynamic PFE usually requires implementing a concentration step prior to the determinative step, and because the extracted analytes are dissolved in a liquid (usually aqueous) phase, SPE is a highly useful tool for avoiding the dilution effect. For this purpose, SPE cartridges and columns packed with appropriate sorbents and coupled online to the extractor outlet can be employed in the same way as commented on for static PEE. Miniaturized retention has also been developed by using solid-phase microextraction (SPME). 

In headspace analysis, the plastic is placed in a vial (at a raised temperature) and the volatiles formed are stripped by a flow of carrier gas. The stripped volatiles are trapped in a suitable sorbent (e.g., using a solid-phase microextraction device) and subsequently thermally desorbed into a gas chromatograph. Process gas chromatographs are used in industrial analysis of volatiles in plastics. An example of this technique is the determination of residual vinyl chloride monomer in plastics in the range of 5-50 g per kg. With direct injection of a polymer solution, there is a danger of side-effects (a loss of reactive monomers due to polymerization in the injection port or an increase in its content due to depolymerization at a high injection temperature). 

Bravo-Sanchez, L.R. Encinar, J.R. Martinez, J.IE Sanz-Medel, A. Mercury speciation analysis in sea water by solid phase microextraction-gas chromatography-inductively coupled plasma mass spectrometry using ethyl and propyl derivatization. Matrix effects evaluation. Spectrochim. Acta B. 2004, 59, 59-66. 

Whichever technique is used for extraction, an additional clean-up procedure is usually included prior to chromatographic analysis in order to minimize matrix effects caused by the presence of coextracted compounds. Sorbent-based (extraction and clean-up) techniques such as SPE [42,43], solid-phase microextraction (SPME) [44-46], matrix solid-phase dispersion (MSPD) [47,48], and MIPs [49,50] are among the most conunonly used. SPE can be used as a direct extraction technique for liquid... 

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