Solvent extraction from coatings

Soybeans. Vktuady ad soybeans processed in the United States are solvent-extracted with hexane to recover the od. This traditional process is outlined in Figure 4. Beans arriving at the plant are cleaned and dried, if necessary, before storage. When the beans move from storage to processing, they are cleaned further and may be dried and adowed to equdibrate at 10—11% moisture to facditate loosening of the seed coat or hud. They are then cracked. 

Solid phase extraction (SPE) is a very simple, rapid and reproducible cleanup technique that is now widely accepted as an alternative to the time-consuming liquid-liquid extractions. Additionally, SPE uses relatively small volumes of solvents, and is easy to automate. It is available in a number of different formats, including cartridges, disks, loose material, well plates or SPME using film-coated capillaries. SPE can be considered as an extraction technique when used for isolation and concentration or a cleanup technique when used to remove co-extractives from solvent extracts. The use of SPE for cleanup is discussed later. 

Applications SFE-SFC solves problems in such diverse areas as polymers/monomers, oils/lubricants, foods, pharmaceuticals, natural products, specialty chemicals, coatings, surfactants and others. Off-line SFE-SFC survives alongside on-line determinations of additives, because of the need for representative sample sizes. Off-line SFE-SFC was used for extraction of AOs from PP [102]. In cases where the analyst wishes to perform further analysis on the extracted species, it is useful to be able to isolate the extract from the solvent. The ability to remove the solvent easily is particularly important when SFE is coupled on-line to chromatographic techniques, but is equally important for trace analysis when it is useful to concentrate... 

Inks, another contaminant of secondary fibers, may be removed by heating a mixture of secondary fibers with surfactants. The removed inks are then dispersed in an aqueous medium to prevent redeposition on the fibers. Continuous solvent extraction has also been used to recover fibers from paper and board coated with plastics or waxes. 

SPME is a sample-preparation technique based on absorption that is useful for extraction and concentration of analytes either by submersion in a liquid phase or exposure to a gaseous phase (Belardi and Pawliszyn, 1989 Arthur et al., 1992). Following exposure of the fiber to the sample, absorbed analytes can be thermally desorbed in a conventional GC injection port. The fiber behaves as a liquid solvent that selectively extracts analytes, with more polar fibers having a greater affinity for polar analytes. Headspace extraction from equilibrium is based on partition coefficients of individual compounds between the food and headspace and between the headspace and the fiber coat-... 

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