Sonication assisted liquid extraction

The classical approach to extract PAHs from lipophilic compounds which are abundant in marine matrices is by means of saponification in basic (NaOH or KOH) alcoholic solution [indicatively see (Webster et al. 2006 Rank 2(X)9)] or the Soxhlet extraction with organic solvents mainly acetone, n-hexane and DCM [indicatively see (Vorkamp et al. 2010 Yoshimine et al. 2012)]. Both methods are widespread, but time consuming. For this reason more fast methods which reduce time, labour and solvent use were pursued by researchers. These include Sonication Assisted Extraction (Maioli et al. 2010 Dsikowitzky et al. 2011), Microwave Assisted Liquid Extraction (MAE) (Cortazar et al. 2008 Zuloaga et al. 2009), and Accelerated Solvent Extraction or Pressurized Liquid Extraction (ASE) usually conducted with the Dionex system (Sloan et al. 2004). Finally the matrix solid-phase dispersion (MSPD) has also been applied to extract PAHs from mussels even in miniaturized scale (Campins-Falco et al. 2008). 

Extraction of solid samples Homogenization extractions Sonication extractions Microwave assisted extractions Soxhlet extractions Accelerated solvent extractions Supercritical fluid extractions Extraction of liquid samples Liquid-liquid extractions Solid phase extractions (SPE)... 

Ultrasound-assisted extraction (USE) is an effective method for leaching many analytes from different kinds of samples [52-55]. It is simple, fast, efficient, and inexpensive in comparison with conventional extraction techniques such as solvent extraction in the Soxhlet apparatus. Ultrasound-assisted solid-liquid extraction is an effective and time-saving extraction method. Sonication accelerates the mass-transfer process between two phases. Use of ultrasound results in a reduction in operating temperature, allowing the extraction of temperature-sensitive components. The ultrasound apparatus is cheaper and its operation is easier in comparison with other novel extraction techniques such as MAE. 

This overview is focused on the on-line coupling of pressurized liquid extraction (PLE), microwave-assisted extraction (MAE), supercritical fluid extraction (SEE) and sonication-assisted extraction (SAE) with liquid and gas chromatography for the analysis of solid agricultural and food samples. In addition, head-space techniques and direct thermal extraction are discussed. 

In the sample preparation of semi- and nonvolatile compounds, solvent extraction is typically used for extracting the analytes of interest from a sample matrix. For volatile analytes, head-space or thermal extraction are good alternatives to solvent-based techniques. Several novel extraction systems that utilize elevated temperatures of pressures in the extraction have been developed particularly for solvent-based extraction methods. These new methods typically are much faster and often more selective than older methods and consume smaller amounts of organic solvents and reagents. Commercially available systems with the ability to heat and pressurize liquids include pressurized liquid extraction (PLE), microwave-assisted extinction (MAE) and supercritical fluid extraction (SFE). Also sonication-assisted extraction (SAE) has given promising results. 

In sonication assisted extraction (SAE), acoustic vibrations with frequencies above 20 kHz are applied to the sample. The vibrations cause cavitation in the liquid that is, bubbles with a negative pressure are formed. When the cavitation bubbles collapse, shock waves are generated, which enhance the removal of analytes from the matrix surface. Moreover, implosion of cavities creates microenvironments of high temperatures and pressures. Traditionally, SAE is performed in static mode. In on-line combinations, the extraction is dynamic 27,28). 

Sanchez-Brunete, C., Rodriguez, A., and Tadeo, J. L., Multiresidue analysis of carbamate pesticides in soil by sonication assisted extraction in small columns and liquid chromatography, J. Chromatogr. A, 1007, 85-91, 2003. 

Techniques. LLE, liquid-liquid extraction LSE, liquid-solid extraction MAE, microwave assisted extraction PLE, pressurized liquid extraction SAE, sonication assisted extraction SEE, supercritical fluid extraction SPE, solid phase extraction TBA, tetrabutylanunonium hydroxide. 

Accelerated solvent extraction (ASE), focused microwave soxhiet extraction (FMSE), immuno affinity cleanup (im-Cu), liquid-liquid extraction (LLE), low-temperature lipid precipitation (LTLP), matrix solid-phase dispersion (MSPD), microwave-assisted extraction (MAE), nanofiltration (NF), pressurized fluid extraction (PEE), single drop microextraction (SOME), solid-phase extraction (SPE), solid-phase microextraction (SPME), steam distillation (SD), stir bar sorptive extraction (SBSE), surpercritical fluid extraction (SFE), subcritical fluid extraction (ScFE), supported liquid membrane extraction (SLME), ultra-sonication (US), size exclusion chromatography (SEC), liquid chromatography-fraction collection (LC)... 

Determination of MC in cyanobacteria, algae, or tissues requires the optimization of additional step in analytical procedure—liquid extraction from these materials. In analysis of cyanobacterial cells, they are most often lyo-philized and then extracted with 75% methanol or with 80% ACN with addition of formic acid."" Double extraction with 75% methanol was also employed for homogenates of algae and fish tissue." In another procedure, extraction of cells with 25% methanol" or 5% acetic acid"° is assisted by sonication. The use of acetic acid instead of methanol is advantageous because of more... 

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. 

Ultrasound-assisted emulsification in aqueous samples is the basis for the so-called liquid membrane process (LMP). This has been used mostly for the concentration and separation of metallic elements or other species such as weak acids and bases, hydrocarbons, gas mixtures and biologically important compounds such as amino acids [61-64]. LMP has aroused much interest as an alternative to conventional LLE. An LMP involves the previous preparation of the emulsion and its addition to the aqueous liquid sample. In this way, the continuous phase acts as a membrane between both the aqueous phases viz. those constituting the droplets and the sample). The separation principle is the diffusion of the target analytes from the sample to the droplets of the dispersed phase through the continuous phase. In comparison to conventional LLE, the emulsion-based method always affords easier, faster extraction and separation of the extract — which is sometimes mandatory in order to remove interferences from the organic solvents prior to detection. The formation and destruction of o/w or w/o emulsions by sonication have proved an effective method for extracting target species. 

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