New extraction techniques

Several authors [92,292,317] have discussed a number of factors affecting SFE from polymers. All classic and new extraction techniques require pre-extraction procedures to ensure that appropriate solvent contact is maximised for solid and semisolid matrices. The preextraction strategies for SFE are given in Table 3.17. 

It has for some time been a common practice to compare new extraction techniques with Soxhlet extraction, and ASE has been no exception in this respect. The ASE technique has many advantages over Soxhlet extraction, especially prominent among which are the following reduced operating times and consumption of organic solvents, and partial automatability. In many cases, ASE provides results similar to (e.g. in the extraction of organophosphorus pesticides, organic matter, hydrocarbons and PAHs from soil... 

Body JJ, Heath H III. Nonspecific increases in plasma immunoreactive calcitonin in healthy individuals discrimination from medullary thyroid carcinoma by a new extraction technique. Chn Chem 1984 30 511-14. 

Dean JR, Liu B, Price R. Extraction of Tanshinone IIA from Salvia miltiorrhiza Bunge using supercritical fluid extraction and a new extraction technique, phytosol solvent extraction. J Chromatogr 1998 799 343-348. 

An increasing demand for new extraction techniques, susceptible to automation, with shorter extraction times and reduced solvent consumption, giving reduced sample preparation costs and preventing pollution in laboratories, has been seen in recent decades. This progress in sample preparation has resulted in new techniques such as microwave assisted extraction (MAE), supercritical fluid extraction (SEE) and accelerated solvent extraction (ASE). These techniques are similar in that they involve working at elevated temperatures and pressures, which improves the speed of the extraction procedure. 

Soxhlet extraction is used as the benchmark against which any new extraction technique is compared. The basic Soxhlet extraction apparatus consists of a solvent reservoir, an extraction body, a heat source (e.g. an isomantle) and a water-cooled reflux condenser (Figure 7.2). A Soxhlet uses a range of organic solvents to remove organic compounds, primarily from solid matrices. The solid sample (ca. 10 g if a soil) and a similar mass of anhydrous sodium sulfate are placed in the porous thimble (cellulose), which in turn is located in the inner tube of the Soxhlet apparatus. The apparatus is then fitted to a round-bottomed flask... 

Extraction of herbicides from solid matrixes has frequently been done by Soxhlet extraction, which required large volumes of solvent and was a time consuming process. Therefore, new extraction techniques have been developed and applied for the past ten years. Herbicides and their main metabolites can be extracted from sohd samples by these new methods such as, SFE, subcritical water extraction (SWE), microwave-assisted extraction (MAE), or pressurized fluid extraction (PFE). From a general point of view. Camel evaluated potentials and pitfalls of SEE, MAE, and PFE. ... 

In the last decade there has been an increasing demand for new extraction techniques, amenable to automation, with shortened extraction times and reduced organic solvent consumption, to prevent pollution and reduce the cost of sample preparation. Driven by these goals, advances in microwave extraction have resulted several techniques such as microwave-assisted solvent extraction (MASE) [32, 36-39], vacuum microwave hydrodistillation (VMHD) [40, 41], microwave hydrodistillation (MWHD) [42, 43], compressed air microwave distillation (CAMD) [44], microwave headspace (MHS) [5], and solvent-free microwave hydrodistillation (SEME) [45, 46]. Table 22.3 summarizes the most common microwave extraction techniques for plant matrices and lists their advantages and drawbacks. Over the years procedures based on microwave extraction have replaced some of the conventional processes and other thermal extraction techniques that have been used for decades in chemical laboratories. 

Microwave-assisted desorption coupled to in situ headspace solid-phase microextraction (HS-SPME) was first proposed as a possible alternative pretreatment of samples collected from workplace monitoring. Therefore, pretreatment that takes a short time and uses little or no organic solvents has led to the recent development of a new extraction technique. Solid-phase micro-extraction (SPME) coupled with GC analysis has been used successfully to analyze pollutants in environmental matrices. MHS has been developed to achieve one-step, in situ headspace sampling of semivolatile organic compounds in aqueous samples, vegetables, and soil [7, 55-58]. 

Romano M, Luciotti G, Gangemi S, Marinucci F, Prontera C, D Urbano E, Davi G Urinary excretion of lipoxin A4 and related compounds Development of new extraction techniques for lipoxins. Lab Invest 2002 82 1253-1254. 

Neither MAE nor ASE is currently in a configuration that would readily lead to the automation of sample preparation. Supercritical fluid extraction can be used as online system that can then be connected to the chromatographic and detection systems. Connected online with the GC/MS, SFE was successfully used for the determination of PAHs in marine sediments. Using either CO2 alone or modified with toluene or MeOH in the extraction, the PAHs were cryofocused in the accumulation cell of the GC and then directly chromatographed. For the study of PAHs in marine sediments, a new extraction technique, which consists of the combination of ASE (dynamic and static mode) and SFE (dynamic mode), was developed, with an extraction time longer than in ASE but shorter than in SFE, and... 

This article studied on a new extraction technique of dietary fiber from Sargassum fusiforme to provide theoretical bases for extensive application. 

Accelerated solvent extraction is a new extraction technique and is performed at high temperature and high pressure. It demonstrates high efficiency, short extraction time, and low solvent usage. Diatomaceous earth was extracted on an accelerated solvent extraction extractor [33] and different solvents (dichloromethane, -hexane, methanol, and ethanol/water (80 20)) are tested. The temperature... 

The miniaturization can be performed by two different approaches by reducing the dimension of the stabilized LLE procedure or by developing new extraction techniques and devices (for applications see Table 23.9). In the former case, the aim lies in the maximum reduction of the ratio between the organic solvent and the sample volumes, so that a better preconcentration factor is obtained. The organic solvent must be water-immiscible and the analytes solubility in the organic solvent should be higher than in the aqueous phase. 

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. 

Fernstrom 1, Johanasson B (1976) Percutaneous pyelolithot-omy. A new extraction technique. Scand J Urol Nephrol 10 257-259... 

Carrapiso, A.I. and Garcia, C., Development in Upid analysis Some new extraction techniques and in situ transesterification. Lipids, 35, 1167-1177, 2000. 

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