Extraction of compound

Mendes, R.L. et al.. Supercritical carbon dioxide extraction of compounds with pharmaceutical importance from microalgae, Inorg. Chim. Acta, 356, 328, 2003. 

Various models of SFE have been published, which aim at understanding the kinetics of the processes. For many dynamic extractions of compounds from solid matrices, e.g. for additives in polymers, the analytes are present in small amounts in the matrix and during extraction their concentration in the SCF is well below the solubility limit. The rate of extraction is then not determined principally by solubility, but by the rate of mass transfer out of the matrix. Supercritical gas extraction usually falls very clearly into the class of purely diffusional operations. Gere et al. [285] have reported the physico-chemical principles that are the foundation of theory and practice of SCF analytical techniques. The authors stress in particular the use of intrinsic solubility parameters (such as the Hildebrand solubility parameter 5), in relation to the solubility of analytes in SCFs and optimisation of SFE conditions. 

SIMS is one of the only mass spectrometric techniques that allow solid samples to be analysed without any extraction of compounds or matrix addition. Generally, no specific preparation technique is required, and solid samples can directly be analysed if they are small enough to be fixed on the sample holder. In most cases, this means that the sample size must not be more than 1 cm. 

Inhibition of radicular growth was stronger with extracts of dry material than those of fresh material and the osmotic pressures of dry material extracts were higher than from fresh material, indicating better extraction of compounds. 

Figure 7.5a The response surface of the partition coefficient of the extraction of compound i used in the validation of the robustness...

Liquid carbon dioxide is a non-polar solvent much like hexane, but in its supercritical state the polarity increases with increase in pressure. By controlling pressure (or by the addition of a polar co-solvent) the selectivity of SC-CO2 can be adjusted for preferential extraction of compounds based on their polarity (19). 

Caro E et al (2006) Application of molecularly imprinted polymers to solid-phase extraction of compounds from environmental and biological samples. TrAC, Trends Anal Chem 25(2) 143-154... 

The most common analytical technique for the analysis of FFAs and their breakdown products has been chromatography. HPLC has been used for the analysis of FFAs (Christie, 1997 Lues et ah, 1998 Zeppa et ah, 2001). Analysis of short-chain fatty acids (C2-C4) may be relatively simple (Zeppa et ah, 2001). However, the analysis of long-chain fatty acids (>C6) may require derivatization. They are extracted using solvents, converted to bromophenacyl esters, and analyzed by reverse-phase HPLC. GC (with sample preparation and derivatization) has been the method of choice for analysis of fatty acids. An ideal but difficult procedure is to extract FFAs from the aqueous phase and organic phase and combine them (IDF, 1991). The challenge is to overcome the effects of partitioning and extraction of compounds that interfere with the analysis. ISO and IDF have detailed some of the extraction methods for lipids and liposoluble compounds in milk products (ISO, 2001b). Several other methods, which are mainly different in the extraction and derivatization steps, were reviewed by Collins et ah (2004). 

Figure 5.1.2 Matrix solid-phase dispersion (MSPD) extraction as a micro-preparative extraction technique for an on-flow LC-NMR-MS screening. Since the latter requires only sample amounts in the 0.5-2 mg range, the sample preparation can be achieved by fast small-scale extraction procedures, such as MSPD. This is a sample preparation technique that combines both sample homogenisation and extraction of compounds of interest in one single step starting from the intact sample material. Thus, it simplifies the extraction and clean-up steps, reduces the sample manipulation and is much faster than conventional techniques. It is therefore very well suited for a rough separation of extracts into classes of compounds of similar polarities, which can then be submitted to LC-NMR-MS analysis...

Of all the materials available for use as a supercritical fluid, CO2 has become the material of choice because of its chemical properties. Instruments have been developed to utilize the principles described to effect extractions of compounds from a variety of sample matrices including asphalt, plant material, and soils (Figure 25.1). The supercritical fluid is pumped through the sample, through a filter or column to a trap where the fluid vaporizes and solvent is added to transfer the analyses to a vial for analysis. More recent instruments combine the supercritical fluid extraction system with a variety of columns and detectors to acquire data from complex samples. 

Furthermore, to increase the efficiency of extraction of basic molecules such as amphetamine, methamphetamine and cocaine, methanol can be acidified with HC1 [151]. Methanol is a good extraction solvent that allows the simultaneous extraction of compounds sensitive to hydrolysis, such as cocaine and heroin, and very lipophilic compounds such as THC [148], A disadvantage of using methanol is an extract with a high level of impurities, which must necessarily be subjected to a subsequent cleanup [42],... 

In the case of selective extraction of compounds from steam distillate after pH adjustment, about 1.5 L distillate were collected by co-distilling 200 g of powdered nuts with 2.5 L of water. The basic, neutral and acidic compounds were extracted using either methylene chloride or ether and the solvent was removed by distillation. In the case of the acidic fraction, the ether extract was methylated by refluxing with methanol-sulphuric acid (50 1) reagent for 2 hours. The methylated samples were washed free of acid and extracted with redistilled hexane, dried and stored frozen. 

When extracting chondroitin sulfate from salmon head cartilage, collagen inevitably accompanies it. In this extraction process, from a pharmaceutical point of view, collagen is considered as an impurity. This is a kind of contradiction because if we administrate chondroitin sulfate and collagen simultaneously, the result will be beneficial and effective. Most marine bioresources contain many health beneficial compounds even in the same tissues. For this reason, we should design sequential extraction processes of those useful compounds from the most value added to the poorly valued compounds. For example, the first step for pharmaceutical use should be the mild extraction of compounds. And the final step should extract materials for fertilizers. 

SBSE can be successfully used in the analysis of environmental samples [93-97] and for food analysis [98, 99]. PDMS is the most commonly used polymer, primarily because of its thermal stability and durability. SBSE has been modified by application of derivatization with different reagents (acetic anhydride, BSTFA, etc) [100-104]. This approach is suitable for the extraction of compounds requiring derivatization. The use of multistep derivatization with several extraction elements (each reaction is performed on a different stir bar) allows efficient extraction, desorption, and chromatographic analysis of compounds with different functional groups (e.g., phenols, steroids, amines, thiazoles, ketones). Acetic anhydride (ester formation), ethyl chloroformate (reaction of acids and amines), tetraethyloborane, and sodium bis-trimethylotrifluoroacetamide have been used for extraction and simultaneous derivatization [105]. 

While analytical derivatizations are an effective way for extracting compounds, these often require additional steps in the analytical procedure and can introduce side products that may interfere with the analysis. Solid phase extraction has provided an alternative method to this process. The advantage of solid phase extraction is that the reagents, derivatives, and side products are maintained on the solid phase. As needed, these derivatives and side products can be selectively eluted after the desired derivative has been formed on the column. In addition, this method can eliminate potential problems associated with emulsion formulation that may occur with liquid-liquid extraction of compounds from the biological matrix. Finally, solid phase extraction is easily amenable to automation with other analytical detection methods such as gas and liquid chromatography. The phases used in solid phase extraction are the standard ones employed in other extraction methods. ... 

Supercritical fluids (SCF) have been used mainly for selective extraction of compounds the solubility of a compound in a given solvent is in many cases vastly different under ambient and supercritical conditions. Thus supercritical water dissolves both polar and nonpolar compounds, which may be explored in electrochemistry. When temperature and pressure approach the critical values, the internal structure of the solvent is loosened and the viscosity, the dielectric constant, and the density diminish the dielectricity constant e of water thus diminishes from 80 at 25°C to 5.2 at 647°C at 221 bar [441]. 

Biological matrices are not directly compatible with LC-MS analysis, since these samples tend to block LC columns and contaminate the ion source. Extraction of compounds of interest from biological fluids is required prior to LC-MS/MS analysis [20]. Sample extraction can be achieved off-line with protein precipitation (PP), liquid-liquid extraction (LLE), or solid-phase extraction (SPE) [21]. With the ease of use and sophistication of automated liquid-handling systems, sample extraction procedures in a 96-well format can handle microliter volumes with multiple sorbents per plate and can simplify and expedite SPE method development [22,23]. The technique can be used to routinely develop methods for multiple analytes and examine a set of eluent compositions for each analyte [16]. 

Examples of the use of these sorbents and their applications will be given in Chapter 7. Finally, a good review of examples of multiresidue extractions of compounds of environmental interest using polymeric and graphitized-carbon sorbents is given by Font and co-workers (1993). 

The selection and development of a reversed-phase method can be a straightforward process, and for this reason, many methods have been developed on reversed-phase SPE, especially the C-18 sorbent due to its reliable nature. The following examples describe the reversed-phase extraction of compounds of differing polarities from various matrices, as an indication of the broad extent to which reversed-phase SPE can be applied. 

Castioni, P, Christen, P., and Veuthey, J. L. 1995. Supercritical fluid extraction of compounds from plant origin, Analusis, 23 95-106. 

Palma, M. Taylor, L. T. Varela, R. M. Cutler, S. J. Cutler, H. G. Fractional Extraction of Compounds from Grape Seeds by Supercritical Fluid Extraction and Analysis for Antimicrobial and Agrochemical Activities , J. Agric. Food Chem., 1999,47,5044. 

---