Ultrasonic extraction matrices

On a laboratory scale, generally an ultrasonic probe (horn) and an ultrasonic cleaner are used. The ultrasonic field in an ultrasonic cleaner is not homogeneous. Sonication extraction uses ultrasonic frequencies to disrupt or detach the target analyte from the matrix. Horn type sonic probes operate at pulsed powers of 400-600 W in the sample solvent container. Ultrasonic extraction works by agitating the solution and producing cavitation in the... 

Brandt [200] has extracted tri(nonylphenyl) phosphite (TNPP) from a styrene-butadiene polymer using iso-octane. Brown [211] has reported US extraction of acrylic acid monomer from polyacrylates. Ultrasonication was also shown to be a fast and efficient extraction method for organophosphate ester flame retardants and plasticisers [212]. Greenpeace [213] has recently reported the concentration of phthalate esters in 72 toys (mostly made in China) using shaking and sonication extraction methods. Extraction and analytical procedures were carefully quality controlled. QC procedures and acceptance criteria were based on USEPA method 606 for the analysis of phthalates in water samples [214]. Extraction efficiency was tested by spiking blank matrix and by standard addition to phthalate-containing samples. For removal of fatty acids from the surface of EVA pellets a lmin ultrasonic bath treatment in isopropanol is sufficient [215]. It has been noticed that the experimental ultrasonic extraction conditions are often ill defined and do not allow independent verification. 

Recovery procedures have traditionally involved some form of solvent, gas or heat extraction from the bulk sample matrix. Some of these lend themselves to precolumn hyphenation (e.g. SFE, TD, Py, HS), as opposed to others (e.g. Soxhlet, ultrasonics). Extraction of additives should not be considered as an isolated step, because it may strongly influence the subsequent chromatographic separation. The success of an analysis may very often depend more on the extraction procedure than on the chromatographic separation. In hyphenation there should be compatibility between the sample preparation and subsequent chromatographic analysis. 

Ideally, the pollutants to be determined should be removed from the matrix as completely as possible with a minimum amount of the other non-target components. This type of selectivity was certainly anticipated from supercritical fluid extraction. However, trace organic pollutants cover a wide range of polarity, volatility, and molecular size, making selective extraction very difficult to achieve. Currently the most popular extraction methods are Soxhlet [191,400, 402-404], blending [189, 408, 409, 411-455], liquid column extraction and ultrasonic extraction [456], and more recently supercritical fluid extraction [386,456-463]. 

Ultrasonic extraction (USE) it is a simple extraction technique, in which the sample is immersed in an appropriate organic solvent in a vessel and placed in an ultrasonic bath. The efficiency of extraction depends on the polarity of the solvent, the homogeneity of the matrix and the ultrasonic time. The mixture of sample and organic solvent is separated by filtration [40,41],... 

Based on the foregoing, efficiency in the extraction of essential oils from plants appears to depend strongly on the particular type of oil and also, possibly, on the sample matrix, so whether SFE surpasses SD-SE in this respect, or vice versa, cannot be stated unambiguously. The SFE technique does surpass ultrasonic extraction (USE) for the removal of organic, low-polar compounds [175-177]. On the other hand, it compares unfavourably with MAE in this respect [177-179]. Thus, Lopez-Avila et al. used MAE, SFE, SOX and USE to extract 94 compounds on the list of EPA method 8250 and found the first technique to provide recoveries above 80% for 51 such compounds, over the range... 

Ultrasonic extraction is an effective method for extracting a number of heavy metals from environmental and industrial hygiene samples.In many cases, it provides quantitative recovery of metals and replaces drastic preparation procedures which would otherwise require the use of concentrated acids and the application of high temperatures and pressures (i.e., hot plate and/or microwave extraction). Quantitative extraction can be achieved for some analytes such as As, Cu, Pb, Cd, etc. from plant and animal tissues. Nevertheless, incomplete extraction has been observed from samples containing a typical inorganic matrix (e.g., sediment). A comparison of conventional... 

Contaminants in the soil can adversely impact the health of animals and humans when they ingest, inhale, or touch contaminated soil, or when they eat plants or animals that have been affected by soil contamination. The exposure of an organism to a carcinogen or other ecotoxic compound in soil is not related to the total concentration of that substance in soil but rather to the amount that is actually available (bioavailability) [34]. Most chemical extraction methods reported in literature were studied in terms of their ability to recover all the contaminants (PAH, pesticides, etc.) from a soil matrix [30,35]. In this chapter we propose the use of a fast and simple analytical extraction method to mimic the bioaccessibility determined by pollution of benzene, naphthalene and anthracene chloride, amino and sulfonate derivatives. The method, based on an ultrasonic extraction [36,37], was performed within a short time (2 minutes) and with a little amount of solvent (10 mL) [31]. 

Sensitive, rapid, simple, and accurate analytical methods have been developed to determine PAHs and their derivatives in the atmospheric particles. Extensively used are GC and coupled methods like GC-FTD, GC-MS, and HPLC-EL as highly efficient separation tools have been used for analyzing aU kinds of samples. The direct determination of traces of PAHs and their derivatives by modem chromatographic techniques is still difficult. There are some limitations associated with the insufficient sensitivity of these techniques and also problems related to matrix interference. For instance in the case of samples of atmospheric particulates, extraction methods of PAHs and their derivatives include traditional Soxhlet extraction, ultrasonic extraction, supercritical fluid extraction, microwave-assisted extraction, and accelerated solvent extraction. ... 

The first step for the determination of PAHs is removal from the matrix by solvent extraction, which preferably is performed with boiling toluene or benzene (hot solvent extraction by refluxing see Jacob and Grimmer 1994), although other solvents (e.g. tol-uene/acetone, acetone, and dichloromethane) and other extraction procedures (ultrasonic treatment, Soxhlet extraction, and accelerated solvent extraction) can also be applied. 

This technique is used mainly for nonpolar compounds. Typically a small aliquot of soil (10-30 g) is dried by mixing with sodium sulfate prior to extraction. Next, the sample is extracted with a solvent for 10-20 min using a sonicator probe. The choice of solvent depends on the polarity of the parent compound. The ultrasonic power supply converts a 50/60-Hz voltage to high-frequency 20-kHz electric energy that is ultimately converted into mechanical vibrations. The vibrations are intensified by a sonic horn (probe) and thereby disrupt the soil matrix. The residues are released from soil and dissolved in the solvent. 

Ra determination in environmental samples (highly saline thermal waters) by ICP-QMS with ultrasonic nebulization has been described by several working groups. Radium was preconcentrated and isolated from the matrix elements by selective extraction using a radium specific solid phase extraction membrane disk designed for radioactive counting methods as proposed by... 

TCBTs are coextracted with PCBs and other lipophilic substances in standard methods of analyses from different environmental matrixes. Waste oil samples were homogenized by ultrasonic shaking, water removed, sample dried by filtration over anhydrous sodium sulfate, and diluted with n-hexane [85]. Water samples (1000 ml) were mixed with 50 ml hexane by Turrax (11,000 rpm). The hexane phase was then dried with anhydrous sodium sulfate [86]. Laboratory water sample (1000 ml) was extracted with three portions of hexane (100 ml, 60 ml, and 60 ml) [87]. Another water sample (50 ml) from laboratory exposure experiments was liquid-liquid extracted with 9 ml of hexane [88]. 

Extraction Shaking, ultrasonication, Soxhlet, liquid-liquid partitioning, solid-phase extraction To extract analytes from sample matrix into solution... 

The solid-solvent mixture is stirred or shaken and then filtered or centrifuged to separate the matrix. Typically three extractions, using small portions of solvent, are needed to assure quantitative extraction. Heating may help in some cases. Or ultrasonic energy (ultrasonic batch or ultrasonic probe) can be used to increase efficiency. Continuous Soxhlet extraction is often used. A Soxhlet extractor has a round-bottom distillation pot, with a porous thimble above it in a siphon chamber, into which the sample is placed. Solvent is continuously cycled through the sample by distilling the solvent to a condenser centered over the thimble. The condensed solvent permeates through the matrix and the thimble, and is siphoned back into the pot, where it is recycled. The extracted material is concentrated in the pot. 

Sample preparation is often more difficult and time-consuming than the actual analysis procedure. Furthermore, extraction of analytes from the matrix is generally the most time-consuming step of sample preparation and it can lead to relatively inefficient analyte recoveries. Off-line supercritical fluid extraction provides an alternative to traditional Soxhlet or ultrasonic liquid extraction methods. Several recent studies have shown analytical SFE provides comparable or better extraction efficiencies than Soxhlet... 

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