Solvent Extraction and Distillation Techniques

T. H. Parliment, Solvent Extraction and Distillation Techniques. In Techniques for Analyzing Food Aroma R. Marsili, Ed. Marcel Dekker New York, 1997 pp 1-26. 

A comprehensive overview of the techniques most commonly used for instrumental analysis of flavor compounds in food has been recently reported [3]. Several methods used for sample treatment are described, as well as the following techniques for extraction prior to GC analysis solvent extraction and distillation techniques, headspace methods, and solid-phase microextraction. The use of GC-olfactometry and of ion-trap MS in food aroma analysis is also described. 

Th. H. Parliment, Solvent extraction and distillation techniques, Techniques for Analyzing Food Aroma (R. MarsiU, ed.), Marcel Dekker, Inc., New York, 1997, p. 1. 

Aumann and Giiner (1999) used PC-RNAA to determine 1 in soil. The combustion technique was used to pre-concentrate iodine that was collected on charcoal, then removed by heat and finally trapped in a quartz vial. Postirradiation purification consisted of solvent extraction and distillation. Szidat et al. (2000) used the same pre-concentration technique... 

The caprolactam obtained must meet die specifications of permanganate number, volatile bases, hazen color, UV transmittance, solidification point, and turbidity in order to be used for repolymerization alone or in combination witii virgin CL.5 Reported CL purification methods include recrystallization, solvent extraction, and fractional distillation. One solvent extraction technique involves membrane solvent extraction. Ion exchange resins have been shown to be effective in the purification of aqueous caprolactam solutions. In one such process,... 

Distillation is probably the most widely used separation technique in the chemical process industries, and is covered in Chapter 11 of this volume, and Chapter 11 of Volume 2. Solvent extraction and the associated technique, leaching (solid-liquid extraction) are covered in Volume 2, Chapters 13 and 10. Adsorption, which can be used for the separation of liquid and gases mixtures, is covered in Chapter 17 of Volume 2. Adsorption is also covered in the books by Suziki (1990) and Crittenden and Thomas (1998). 

Acetic acid is an important intermediate organic tonnage chemical that may be produced by the petroleum industry and fermentation. The latter process requires the recovery of acetic acid from water solutions, and several techniques have been applied to this separation, including solvent extraction, azeotropic distillation, and extractive distillation. A comparison of economics between azeotropic distillation and solvent extraction combined with azeotropic distillation (Table 10.3) shows that the introduction of... 

Solutions must be concentrated or the constituents must be isolated before trace amounts of the various organics present as complex mixtures in environmental water samples can be chemically analyzed or tested for toxicity. A major objective is to concentrate or isolate the constituents with minimum chemical alteration to optimize the generation of useful information. Factors to be considered in selecting a concentration technique include the nature of the constituents (e.g., volatile, nonvolatile), volume of the sample, and analytical or test system to be used. The principal methods currently in use involve (1) concentration processes to remove water from the samples (e.g., lyophilization, vacuum distillation, and passage through a membrane) and (2) isolation processes to separate the chemicals from the water (e.g., solvent extraction and resin adsorption). Selected methods are reviewed and evaluated. 

The precipitation technique is often applied in the primary step and/or the final step of a procedure in which another technique of rapid separation, such as recoil, solvent extraction, or distillation, is used. 

Extraction of Essential Oils from Plants. Essential oils are aromatic substances widely used in the perfume industry, the pharmaceutical sector, and the food and human nutrition field. They are mixtures of more than 200 compounds that can be grouped basically into two fractions a volatile fraction, which constitutes 90-95% of the whole oil, and a nonvolatile residue, which constitutes the remaining 5-10%. The isolation, concentration, and purification of essential oils have been important processes for many years, as a consequence of the widespread use of these compounds. The common methods used are mainly based on solvent extraction and steam distillation. SFE has been used for the extraction of essential oils from plants, in an attempt to avoid the drawbacks linked to conventional techniques (57). Such is the case with the extraction of flavor and fragrance compounds, such as those from rose (58), rosemary (59), peppermint (60), eucalyptus (61), and guajava (62). The on-line coupling of the extraction and separation ietermi-nation steps (by SFE-GC-FID) has been proposed successfully for the analysis of herbs (63) and for vetiver essential oil (64). 

Moldoveanu, S.C., J.L. Roles, and Q. Zha Study of the volatile compounds from tobacco using steam distillation-solvent extraction and other extraction techniques 50th Tobacco Chemists Research Conference, Program Booklet and Abstracts, Vol. 50, Paper No. 42, 1996, pp. 44-45. 

As mentioned previously, many instrumental methods can handle a sample as it is. Sometimes processing is called for to comply with standardized procedures or to create conditions for the specific determination of a substance. In trace analysis, sample processing is performed to concentrate a trace constituent to a level at which it can be determined by a given instrumental technique or to eliminate interfering constituents, or both. Some of the techniques used are solvent extraction, evaporation, distillation, precipitation and ashing. 

Frequently a concentration step is desirable in the pretreatment of a sample. If the sample can be placed in solution, several concentration techniques are available, including precipitation, ion exchange, solvent extraction, and electrolysis. Concentration steps are more difficult if the sample must remain a solid some possibilities for solid powder samples include high-temperature distillation, flotation, and magnetic separation. 

Tassios, D.P., Rapid screening of extractive distillation solvents Predictive and experimental techniques, in Extractive and Azeotropic Distillation, Advances in Chemistry Series No. 115, American Chemical Society, Washington, DC, 1972. Chapter 4. 

Reports about static HSGC and flavour research of fats and oils are scarce. HSGC can be used to good advantage when the primary aim of an analysis is quantification of target components, for example pentane or hexanal in oxidized oils. For an in-depth investigation of lipid-related flavours more sensitive techniques have to be used (Reineccius, 1989). Dynamic HS, simultaneous distillation and solvent extraction and high-vacuum... 

Fermentation-derived lactic acid can be separated by several recoveiy processes, which include calcium precipitation, solvent extraction and electrodialysis.Other recovery techniques have also been reported such as direct distillation, adsorption, liquid surfactant membrane extraction, chromatographic approaches, ultrafiltration, reverse osmosis, drying, conventional electrodialysis as well as bipolar membrane electrodialysis. ... 

In many production processes, a wet chemical procedure is unavoidable. In general, solvent extraction and ion-exchange techniques are commonly used, but occasionally methods like coprecipitation, adsorption, wet distillation, electrodeposition etc., are preferred. The separation procedure finally adopted often depends on the speciality of a laboratory. 

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