Antioxidants separation techniques

Oleosomes of seabuckthom fruit flesh were isolated by physical separation techniques and their higher stabilities and antioxidant activities compared to solvent-extracted oil were demonstrated. ... 

Applications Conventional TLC was the most successful separation technique in the 1960s and early 1970s for identification of components in plastics. Amos [409] has published a comprehensive review on the use of TLC for various additive types (antioxidants, stabilisers, plasticisers, curing agents, antistatic agents, peroxides) in polymers and rubber vulcanisates (1973 status). More recently, Freitag [429] has reviewed TLC applications in additive analysis. TLC has been extensively applied to the determination of additives in polymer extracts [444,445]. 

J. McAndless, Defense Research, Ottawa The C-13 NMR technique seems quite good for identifying the major component in the rubber formulations, namely the rubber itself. Is the technique sufficiently sensitive to pick out the antioxidants and the processing oils without having to go through the normal separation techniques ... 

P. K. J. P. D. Wanasundara Agriculture and Agri-Food Canada, Saskatoon Research Center, Saskatoon, Saskatchewan, Canada, Antioxidants Science, Technology, and Applications, Novel Separation Techniques for Isolation and Purification of Fatty Acids and Oil By-Products. 

Antioxidant and antiozonant types most commonly used are aromatic amines or phenolics, though others are also employed, and can be determined using a variety of techniques such as UV-visible spectrophotometry, FTIR, near-infrared spectroscopy, TEC, GC (if the material can be volatilized), supercritical fluid chromatography, and HPLC. Identification of unknown antioxidants requires a separation technique like chromatography followed by mass spectrometry, NMR, ETIR, X-ray crystallography, etc. Standardized TEC methods are given in ASTM D3156 and... 

OIT/Tox measurements provide rapid and reliable results. Many materials contain a system of antioxidants, often a combination of a primary antioxidant (hindered phenol or amine) and a secondary antioxidant (phosphite, thioester, etc.). Thermal analysis provides no information about the concentration of the different antioxidants separately but rather an overall assessment of the stability. Extraction followed by chromatography (HPLC) is one of the main techniques for the determination of antioxidant concentration, but it is no doubt much more time-consuming than DSC/DTA. 

Despite these applications, disadvantages such as requirement of large sample amounts may restrict the use of TLC compared to column methods because such amounts are not always available. On the other hand, recovery of the antioxidant from TLC plates could also be challenging. In this sense, most TLC applications are restricted to the fractionation and preliminary separation of antioxidant flavonoids before they are separated, quantified, and identified by high-performance liquid chromatography (HPLC) or other high-performance separation techniques. 

More recently, the same author [41] has described polymer analysis (polymer microstructure, copolymer composition, molecular weight distribution, functional groups, fractionation) together with polymer/additive analysis (separation of polymer and additives, identification of additives, volatiles and catalyst residues) the monograph provides a single source of information on polymer/additive analysis techniques up to 1980. Crompton described practical analytical methods for the determination of classes of additives (by functionality antioxidants, stabilisers, antiozonants, plasticisers, pigments, flame retardants, accelerators, etc.). Mitchell... 

Polymer/additive analysis then usually proceeds by separation of polymer and additives (cf. Scheme 2.12) using one out of many solvent extraction techniques (cf. Chapter 3). After extraction the residue is pressed into a thin film to verify that all extractables have been removed. UV spectroscopy is used for verification of the presence of components with a chromophoric moiety (phenolic antioxidants and/or UV absorbers) and IR spectroscopy to verify the absence of IR bands extraneous to the polymer. The XRF results before and after extraction are compared, especially when the elemental analysis does not comply with the preliminary indications of the nature of the additive package. This may occur for example in PA6/PA6.6 blends where... 

Figure 12 Separation of Irganox 1076 and Irganox PS802 by size exclusion chromatography (duplicate solution injections of each antioxidant showing the reproducibility of the technique).

Step 3—In a separate step, styrene-acrylonitrile (SAN) resin is prepared by emulsion, suspension, or mass polymerization by free-radical techniques. The operation is carried out in stainless-steel reactors operated at about 75°C (167°F) and moderate pressure for about 7 hours. Tlie final chemical operation is the blending of the ABS graft phase with the SAN resin, plus adding various antioxidants, lubricants, stabilizers, and pigments. Final operations involve preparation of a slurry of fine resin particles (via chemical flocculation), filtering, and drying in a standard fluid-bed dryer at 121-132°C (250-270°F) inlet air temperature. 

The multiple functions of peptides in foods (antioxidants, antimicrobial agents, surfactants) and their role in the development of characteristic flavors (sweetness, bitterness), as well as the information they can provide about the genuineness of foods, make peptide analysis a necessity. Producers as well as government laboratories have considerable interest in the study of peptides, both for research purposes and for the control of raw materials and manufactured foods. For this reason, substantial attention is now being focused on the development of analytical techniques designed to separate, characterize, and quantify peptides. 

Hall et al. (127) compared free solution capillary electrophoresis (FSCE) and micellar elec-trokinetic capillary chromatography (MEKC) techniques with HPLC analysis. Four major food-grade antioxidants, propyl gallate (PG), BHA, BHT, and TBHQ, were separated. Resolution of the 4 antioxidants was not successful with FSCE, but was with MEKC. Separation was completed with excellent resolution and efficiency within 6 min and picomole amounts of the antioxidants were detectable using UV absorption. In contrast, reversed-phase HPLC separation was not as efficient and required larger sample amounts and longer separation time. 

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