Accelerated solvent extraction advantages

Another method (EPA 3545, accelerated solvent extraction) has been validated using a variety of soil matrixes, ranging from sand to clay. In the method, conventional solvents such as methylene chloride (or a hexane-acetone mixture) are heated [100°C, (212°E)] and pressurized (2000 psi), then passed through the soil sample (this technique is also suitable for application to petroleum sludge and petroleum sediment). The method has the advantage of requiring smaller solvent volumes than is required by traditional solvent extraction techniques. 

This technique, as discussed above under Accelerated Solvent Extraction , has the outstanding advantage that extraction with water as opposed to organic solvents does not cause contamination of the extract with potentially interfering organic components such as cellulose, lignin and waxes originating in plant cells or interference due to contamination by the solvent or impurities therein. 

The extraction of pesticides from soil samples using accelerated solvent extraction is a good example of an analytical procedure fulfilling the rules of green chemistry. This procedure has many advantages over the classical techniques used for extracting analytes from complex matrices. 

Accelerated solvent extraction, like many other recent techniques, has frequently been compared with well-established, other solid-liquid extraction techniques in order to assess its potential in various fields and identify its advantages and disadvantages relative to existing alternatives. 

A number of alternatives to Soxhlet extraction have been described. By pressurized liquid or accelerated solvent extraction, the extraction efficiency can be enhanced. Superheated water extraction, taking advantages of the decreased polarity of water at higher temperature and pressure, has been used for liquid extraction of solid samples as well. 

Many of the above-mentioned advantages also apply to liquids that have been raised to near-supercritical (but subcritical) regions (20). These properties are exploited in accelerated solvent extraction that employs high pressure at elevated temperatures. The increased temperature also increases the volatility of the analytes and their solubility in the solvent. Thus SFE may be... 

Accelerated solvent extraction (ASE) is a relatively recent advance in sample preparation for trace environmental analysis. This techiuque uses conventional solvents at elevated pressures and temperatures to extract solid samples quickly. The process takes advantage of the increased analyte solubilities at temperatures well above the boiling points of common solvents. Under these conditions, the kinetic processes for the desorption of analytes from the matrix are accelerated. Currently a commercial unit is available in which automated extractions can be carried out on 24 samples sequentially (Richter et al., 1995, 1996). This technique offers some significant advantages over SEE and MAP. SEE uses supercritical CO2, which is a nonpolar fluid, whereas MAP requires the presence of a polar solvent that couples with microwave to promote heating. By comparison, ASE uses the same solvent as traditional Soxhlet extractions, which means a (firect transfer of methodology is feasible without any of the restrictions or limitations of the two other methods. Method development time is therefore shortened. 

Special, fully automated instruments are available for ASE these include an extraction cell (1 up to 100 ml), which is maintained at a temperature between 80 and 200°C, into which a solvent is pumped and maintained at 10—20 MPa for some minutes. Then, a second volume of solvent carries the extract into a collection vial finally, the solvent is removed by flushing an inert gas. The main advantages of ASE are the high extraction yield combined with short extraction time and reduced solvent consumption. For the separation of volatile and semi-volatile components, accelerated solvent extraction gives recoveries comparable to those obtained with Soxhlet and other solvent-extraction techniques... 

The ionic liquid can be recovered after extracting the product with ether. The recovered ionic liquid can be reused. The ionic liquid played the dual role of solvent and promoter. This method consists many obvious advantages compared to the conventional methods, including rate acceleration, environmentally more benign, and... 

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