Solid-phase microextraction solvent extraction

In 2003, Smith reviewed newer sample preparation techniques, including pressurized liquid extraction, solid phase microextractions, membrane extraction, and headspace analysis. Most of these techniques aim to reduce the amount of sample and solvent required for efficient extraction. 

Saponins from plant materials can be extracted using different techniques and solvents. The conventional techniques for saponin extraction used soxhlet, liquid-liquid or solid-liquid extraction (Berhow et al. 2002 Hassan et al. 2010a, b). These methods consume a lot of solvent, time and may lead to potentially deleterious degradation of labile compounds (Kerem et al. 2005). Therefore, in recent years, new extraction techniques include accelerated solvent extraction, supercritical fluid extraction, solid-phase microextraction, sonication, extraction with supercritical or subcritical water, and microwave-assisted extraction have been developed and are considered to be more efficient than the conventional methods (Wu et al. 2001 Kerem et al. 2005 Ligor et al. 2005 Gii lii-Ustundag and Mazza 2007). Ultrasonication-assisted extraction of ginseng saponins was about three times faster than the liquid-liquid extraction and can be carried out at lower temperature (Wu et al. 2001). Kerem et al. (2005) reported that methanol- microwave assisted method to extract saponin of chiclqtea proved to be faster and more efficient than soxhlet extraction. 

In recent decades the development of preconcentration steps to be implemented prior to analytical determinations of trace level compounds has been explored in considerable depth. With a view to eliminating or at least minimising the use of organic solvents used in conventional liquid-liquid extraction, other methodologies have been developed, such as membrane extraction, solid-phase extraction, solid-phase microextraction, etc. 

Shen, S. et al.. Comparison of solid-phase microextraction, supercritical fluid extraction, steam distillation, and solvent extraction techniques for analysis of volatile consituents in Fructus amomi, J. AOAC Int., 88, 418, 2005. 

Several extraction methods for water samples are applicable, such as solvent extraction, SPE using a cartridge and disk and solid-phase microextraction (SPME). 

The need to understand the fate of pesticides in the environment has necessitated the development of analytical methods for the determination of residues in environmental media. Adoption of methods utilizing instrumentation such as gas chro-matography/mass spectrometry (GC/MS), liquid chromatography/mass spectrometry (LC/MS), liquid chromatography/tandem mass spectrometry (LC/MS/MS), or enzyme-linked immunosorbent assay (ELISA) has allowed the detection of minute amounts of pesticides and their degradation products in environmental samples. Sample preparation techniques such as solid-phase extraction (SPE), accelerated solvent extraction (ASE), or solid-phase microextraction (SPME) have also been important in the development of more reliable and sensitive analytical methods. 

During the last few years, miniaturization has become a dominant trend in the analysis of low-level contaminants in food and environmental samples. This has resulted in a significant reduction in the volume of hazardous and expensive solvents. Typical examples of miniaturization in sample preparation techniques are micro liquid/liquid extractions (in-vial) and solvent-free techniques such as solid-phase microextraction (SPME). Combined with state-of-the-art analytical instrumentation, this trend has resulted in faster analyses, higher sample throughputs and lower solvent consumption, whilst maintaining or even increasing assay sensitivity. 

Solid-phase microextraction eliminates many of the drawbacks of other sample preparation techniques, such as headspace, purge and trap, LLE, SPE, or simultaneous distillation/extraction techniques, including excessive preparation time or extravagant use of high-purity organic solvents. SPME ranks amongst other solvent-free sample preparation methods, notably SBSE (Section 3.5.3) and PT (Section 4.2.2) which essentially operate at room temperature, and DHS (Section 4.2.2),... 

Diffusive sampler Membrane extraction (MESI) Liquid-liquid extraction (LLE) Solid-phase extraction (SPE) SPE-PTV-GC Solid-phase microextraction (SPME) Headspace GC (SHS, DHS) Large-volume injection (LVI) Coupled HPLC-GC Membrane extraction (MESI) Difficult matrix introduction (DMI) Conventional solvent extraction methods 1 Pressurised solvent extraction methods Headspace GC (SHS, DHS) Thermal desorption (TD, DTD) Pyrolysis (Py) Photolysis Photon extraction (LD) Difficult matrix introduction (DMI)... 

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],... 

Miniaturisation of scientific instruments, following on from size reduction of electronic devices, has recently been hyped up in analytical chemistry (Tables 10.19 and 10.20). Typical examples of miniaturisation in sample preparation techniques are micro liquid-liquid extraction (in-vial extraction), ambient static headspace and disc cartridge SPE, solid-phase microextraction (SPME) and stir bar sorptive extraction (SBSE). A main driving force for miniaturisation is the possibility to use MS detection. Also, standard laboratory instrumentation such as GC, HPLC [88] and MS is being miniaturised. Miniaturisation of the LC system is compulsory, because the pressure to decrease solvent usage continues. Quite obviously, compact detectors, such as ECD, LIF, UV (and preferably also MS), are welcome. 

In the 1990s, Pawliszyn [3] developed a rapid, simple, and solvent-free extraction technique termed solid-phase microextraction. In this technique, a fused-silica fiber is coated with a polymer that allows for fast mass transfer—both in the adsorption and desorption of analytes. SPME coupled with GC/MS has been used to detect explosive residues in seawater and sediments from Hawaii [33]. Various fibers coated with carbowax/divinylbenzene, polydimethylsiloxane/divinylbenzene, and polyacrylate are used. The SPME devices are simply immersed into the water samples. The sediment samples are first sonicated with acetonitrile, evaporated, and reconstituted in water, and then sampled by SPME. The device is then inserted into the injection port of the GC/MS system and the analytes thermally desorbed from the fiber. Various... 

The mass of sample taken for analysis is primarily dependent on four factors (1) the amount of material available, (2) the concentration of the analyte, (3) the heterogeneity of the sample, and (4) the method of analysis. Most conventional solvent extraction techniques currently start with more sample than is required, use more extraction solvent than is necessary, and ultimately only analyze 0.1% of the material prepared, e.g., 1 pi from 1 ml. Micro-extraction techniques [468] can be used in conjunction with on-line LC-GC or LC-MS to utilize the whole extract in the final determinations. This approach can significantly reduce the size of sample required and the volume of solvent used. Many workers have reported the use of solid phase microextraction (SPME) in different environmental matrices for various pollutants [288,342,345,469 - 477]. 

In this work, we adapted a method for the analysis of beer aldehydes using solid-phase microextraction (SPMF) with on-fiber derivatization. This extraction technique does not require solvents, consists of a one-step sample preparation procedure, and provides high sensitivity and reproducibility. It enabled a detailed study of aldehyde level changes during packaged beer storage. 

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)... 

Solid-phase microextraction (SPME), a new solvent-free sample preparation technique, was invented by C. Arthur and J. Pawliszyn in 1990. This method was mainly applied for the extraction of volatile and semivolatile organic pollutants in water samples. However, since 1995, SPME has been developed to various biological samples, such as whole blood, plasma, urine, hair, and breath, in order to extract drags and poisons in forensic field. The main advantages of SPME are high sensitivity, solventless, small sample volume, simplicity, and rapidity (Liu et al., 1998). 

Besides classical headspace analysis, simultaneous distillation-extraction and solvent extraction, new sampling and enrichment developments include solvent-assisted flavour evaporation (SAFE) [3] and sorptive techniques like SPME solid-phase microextraction (SPME) [4,5] and stir-bar sorptive extraction (SBSE) [6], which are treated in a dedicated chapter in this book. This contribution will deal with advanced developments of GC techniques for improvement of separation and identification (classical multidimensional GC, or... 

Recently, the procedures that are suitable to isolate the volatile fraction of a sample under mild conditions have been reviewed [1]. Three techniques—solvent extraction, distillation and solid-phase microextraction (SPME)—will be presented here. 

Headspace gas or solvent extract (unttgi.i) from sample of interest Solid-phase microextraction (SPME) fiber, containing sample of interest (unit G 1.6)... 

Wennrich et al. [97] have described a method for the determination of nine chlorophenols in soil using accelerated solvent extraction with water as the solvent combined with solid-phase microextraction and gas chromatography - mass spectrometry. An extraction temperature of 125 °C and ten-minute extractions were optimal. 

Supercritical fluid extraction [153,154], accelerated solvent extraction [68] and subcritical fluid extraction [107,155] have been studied. To reduce the equipment cost and the analysis time in the extraction process and sample preconcentration, a solid-phase microextraction method was proposed by Pawliszyn and coworkers [156-158]. 

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. 

Wennrich et al. [167] investigated the capabilities of coupling accelerated solvent extraction with water as the extraction solvent and solid-phase microextraction to determine chlorophenols in polluted soils. Subcritical water extraction was performed using a commercially available accelerated solvent extractor. This system solves the problem of the analytes partitioning back to the soil matrix, which can occur in straightforward subcritical water extraction because in the Wennrich et al. method [167] the aqueous phase and the soil are separated under the extraction conditions. 

Solvent extraction Microwave extraction Solid phase microextraction Subcritical water extraction Subcritical water extraction Supercritical fluid extraction... 

Solid-phase microextraction [320-322], microwave-assisted extraction [321, 323], accelerated solvent extraction and Soxhlet extraction have been discussed [324,325]. 

Another alternative technique, solid-phase microextraction (SPME), was used for the determination of fluoxetine [79] and several TCAs [80], SPME is a miniaturized and solvent-free technique, where analytes are extracted from the sample by adsorption on a thin polymer coating fixed to the solid surface of a fiber, located inside an injection needle or a capillary. Its main disadvantage is that special strategies are needed to couple SPME to the LC-MS analysis. 

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