Extraction of organic compound from solid

Other organic compounds such as phenols [40], hydrocarbons [267], polymer additives [268,269] and natural compounds [270] have also been extracted from a wide range of solid matrices with good results. This confirms that, under optimal conditions of solvent, microwave power and exposure time, etc., the MAE technique is suitable for the extraction of organic compounds from solid samples. 

ASTM D6010. Standard Practice for Closed Vessel Micro-wave Solvent Extraction of Organic Compounds from Solid Matrices, American Society for Testing and Materials, Philadelphia, PA, 1996. 

Soxhlet extraction is one of the most conventional techniques for extraction of organic compounds from solid matrices. It was applied early to the analysis of DEP and other phthalate esters in sediments and soils, using different extraction solvents such as hexane, dichloromethane or even acetonitrile, and is still considered as the reference method for the extraction of semivolatile compounds from solid environmental samples. The major disadvantages to Soxhlet extraction are length of time and consumption of solvent. 

Laitinen, A. Supercritical fluid extraction of organic compounds from solids and aqueous solutions. Technical Research Centre of Finland, VTT Finland, 1999, pp. 58-84. 

D. L. Mayer and J. S. Fritz, Semi-micro solid-phase extraction of organic compounds from aqueous and biological samples,/. Chromatogr. A, 773,189,1997. 

The focus in Chapters 7 and 8 is on the specific sample preparation approaches available for the extraction of organic compounds from environmental matrices, principally soil and water. Chapter 7 is concerned with the role of Soxhlet, ultrasonic and shake-flask extraction on the removal of organic compounds from solid (soil) matrices. These techniques are contrasted with newer developments in sample preparation for organic compound extraction, namely supercritical fluid extraction, microwave-assisted extraction and pressurized fluid extraction. Chapter 8 is arranged in a similar manner. Initially, details are provided on the use of solvent extraction for organic compounds removal from aqueous samples. This is followed by descriptions of the newer approaches, namely solid-phase extraction and solid-phase microextraction. 

Sorbent extraction Sorbent extraction makes use of the differential distribution of the dissolved compounds between the solid sorbent and water. The use of organic porous polymers is advantageous for the extraction of organic compounds from water because (1) the partition coefficients of compounds in a polymer-water system reach infinity if the correct polymer is selected for the types of contaminants present (2) adsorption of water itself on the polymer is minimal (3) the wettability of the polymer with water makes possible satisfactory transport of the substance toward the polymer surface and (4) the polymer is inert. 

Supercritical fluid extraction (SFE) and Solid Phase Extraction (SPE) are excellent alternatives to traditional extraction methods, with both being used independently for clean-up and/or analyte concentration prior to chromatographic analysis. While SFE has been demonstrated to be an excellent method for extracting organic compounds from solid matrices such as soil and food (36, 37), SPE has been mainly used for diluted liquid samples such as water, biological fluids and samples obtained after-liquid-liquid extraction on solid matrices (38, 39). The coupling of these two techniques (SPE-SFE) turns out to be an interesting method for the quantitative transfer... 

Although selective extraction of organic compounds appears to be an attractive option, the different types of adsorption sites on solid phases require an exhaustive technique to recover the maximum amount of the analyte from the... 

Stir bar sorptive extraction (SBSE), an approach theoretically similar to SPME, was recently introduced [141] for the trace enrichment of organic compounds from aqueous food, biological, and environmental samples. A stir bar is coated with a sorbent and immersed in the sample to extract the analyte from solution. To date, reported SBSE procedures were not usually operated as exhaustive extraction procedures however, SBSE has a greater capacity for quantitative extraction than SPME. The sample is typically stirred with the coated stir bar for a specified time, usually for less than 60 minutes, depending on the sample volume and the stirring speed, to approach equilibrium. SBSE improves on the low concentration capability of in-sample solid-phase microextraction (IS-SPME). 

EXTRACTION OF SEMIVOLATILE ORGANIC COMPOUNDS FROM SOLID MATRICES... 

It should be noted that microwave-assisted extraction (MAE) discussed in this chapter is different from microwave-assisted acid digestion. The former uses organic solvents to extract organic compounds from solids, while the latter uses acids to dissolve the sample for elemental analysis with the organic contents being destroyed. Microwave-assisted digestion of metals is covered in Chapter 5. 

EXTRACTION OF VOLATILE ORGANIC COMPOUNDS FROM SOLIDS AND LIQUIDS... 

Liska, I., Krupcik, J., and Leclercq, P. A. 1989. The use of solid sorbents for direct accumulation of organic compounds from water matrices—A review of solid-phase extraction techniques, J. High Resol. Chromatog., 12 577-590. 

Solid phase micro extraction (SPME) fibres have improved in quality over the last few years and are now commonly used for introducing analytes into a gas chromatograph [1,2], The technique utilises a one cm length of fused silica coated with an adsorbent or absorbent phase. This allows preconcentration of organic compounds from a volatile or liquid sample that are adsorbed or absorbed in the fibre. The fibre is inserted into a heated injector port of a gas chromatograph where the analytes are thermally desorbed directly onto the column. The fibres are made up of a variety of coatings, of which the most common ones are shown in Table 1. 

It is well known that ultrasound has been applied to some organic substrates of environmental interest either to convert them to compounds which are less harmful than the original substrates or to extract species from particulate matter. Sonication is usually recommended for pretreatment of solid environmental samples for the extraction of nonvolatile and semivolatile organic compounds from solids such as soils, sludges and wastes since unsophisticated instrumentation may be used and separations can be performed in a short time using diluted reagents and low temperatures. 

Sample preparation methods involve the extraction of volatile compounds from their matrices. Extraction of organic volatile compounds from environmental matrices has been carried out using gases, liquids, or solids. Nowadays, most sample preparation methods for the analysis of VOCs in water use gases or solids as extracting agents because liquid-liquid extraction methods (LEE) present several disadvantages ... 

Ultrasonic LSE is most applicable to the isolation of semivolatile and nonvolatile organic compounds from solid matrices such as soil, sediment, clays, sand, coal tar, and other related solid wastes. U-LSE is also very useful for the disruption of biological material such as serum or tissue. U-LSE can be coupled with solid-phase extraction (SPE) to give a very robust sample preparation method at relatively low cost in comparison to MAE and ASE approaches. The author has utilized U-LSE/SPE to isolate and recover 9,10-dimethyl-l,2-benzanthracene from animal bedding. A 89% recovery was obtained for bedding that was spiked with this polycyclic aromatic hydrocarbon (PAH) of interest to toxicologists (20). An ultrasonic horn and tip are immersed into a mixture of liquid extractant and solid sample and sonicated at some percent of full power for a finite length of time, either continuously or pulsed. 

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