Antioxidant mixtures

Direct liquid injection (DLI) has been used even less. Hirter et al. [579] have reported the early analysis of a synthetic antioxidant mixture (Irganox 1010/1076/1098) by means of iRPLC-DLI-QMS with Cl. In early studies, the HPLC effluent was vaporised by laser radiation [593] both El and solvent-mediated Cl spectra were obtained in the on-line mode from analytically difficult molecules. However, the instrumentation was complex the sensitivity was not as good as that obtained by GC-MS and thermal decomposition was observed with other compounds. This direct introduction approach with enrichment was used for the analysis of phthalates. 

As mentioned previously, in the AMD retina iron metabolism is compromised (He et al., 2007 Wong et al., 2007). Thus, it is of interest to determine the effects of potential antioxidants in the presence of iron. In an in vitro study of ARPE-19 cells, addition of a lipophilic iron complex led to about a ninefold increase in the photosensitized yield of 7a,(3-cholesterol hydroperoxides (Wrona et al., 2004). In the presence of the iron, ascorbate exerted pro-oxidant effects, while the effects of a-tocopherol, zeaxanthin, or their combination were still protective (Wrona et al., 2004). Thus, it appears that the effects of potential antioxidants are strongly dependent on the sources of oxidative damage. The same antioxidant may be protective under certain conditions and exert deleterious effects when the conditions are changed. Therefore a detailed understanding of the sources of the oxidative damage is required in order to design an adequate antioxidant mixture. 

Table 4 Comparison of the antioxidant performance (accelerated UV ageing) of synergistic mixture (melt grafted in presence of Tris) with a conventional antioxidant mixture based on the same antioxidant functions (at 1 1 w/w ratio)...

Pongracz G. Antioxidant mixtures for use in food. Int] Vitam Nutr Res 1973 43 517-525. 

Since there are synergistic effects between antioxidants, commercial preparations usually contain mixtures of these antioxidants. As oxidative rancidity is strongly catalyzed by some heavy metal ions, in particular QT+, antioxidant mixtures often contain sequestrants (e.g., citric acid and ethylenediaminetetraacetic acid (EDTA)) in order to complex these ions. Reductants such as ascorbic acid, which decrease the local concentration of oxygen, are also able to decrease the formation of peroxy radicals. 

Activity of Natural Antioxidant Mixtures against Lipid Oxidation.397... 

During the last years, appropriate SPME extraction techniques have been developed and successfully applied during oxidation of food related o/w emulsions in order to describe their volatile profile during oxidative deteroration. It has been found that the use of natural antioxidant mixtures has effectively inhibited the production of volatile aldehydes - and thereby protect the final products from their organoleptic and nutritional deterioration. Kiokias and Oreopoulou described the profile of certain aldehydes, extracted with SPME during oxidation of sunflower o/w emulsions. 

Actis-Goretta, L., Carrasquedo, R, and Fraga, C.G., The regular supplementation with an antioxidant mixture decreases oxidative stress in healthy humans. Gender effect, Clin. Chim. Acta, 349, 97-103, 2004. 

Catecholamine stock solutions. 0.1 mg/mL in antioxidant mixture (see Section 2.1., item 8). Prepare separate stock solutions of NAD, AD, and DA by dissolving 5 mg of each in 50 mL of filtered antioxidant mixture. Stored at 4°C in brown glass bottles or glass bottles covered with alummiun foil, the solutions are stable for 2 mo... 

Trace a baseline (see Note 11). If it is acceptable, inject a blank (e.g., Ringer s-antioxidant mixture see Note 12). If no interfering peaks are observed, inject the three standards of the CA and establish a calibration curve (see Note 13)... 

When working with an automated LC system, it is essential that stability of the monoamine samples be maintained during the duration of analysis (usually about 20 h). For the CA analysis, we observed that for larger amounts of DA in the dialysates (as is the case in samples from the striatum) the amount of antioxidant mixture (see Section 2.1., item 8) added to the samples must be increased. Therefore, for 40 uL dialysates from the striatum, we add 40 jjL of antioxidant mixture, whereas for 40 juL samples of the substantia nigra or hippocampus, only 10 juL of antioxidant is added. To ensure stability of the analytes, dialysates are collected into a vial already containing the appropriate volume of antioxidant mixture (see Notes 14 and 15). 

These types of DNA detection can also be applied to studies of antioxidative properties of various natural substances preserving DNA from damage [49, 50]. The detection scheme exploits quantification of the DNA portion that survives previous incubation of the biosensor in a mixture of the DNA cleavage agent and antioxidant/mixture of antioxidants under investigation. Using this approach, yeast polysaccharides, phenolic acids such as rosmarinic and caffeic acids, selected flavonoids, as well as aqueous plant extracts and tea extracts were studied [51]. 

Loliger, J. and Saucy, F. A synergistic antioxidant mixture. European patent 0326S29 (1989) ... 

The LD-MS of Compound 8, which contains the Wingstay 300 antiozonant and an aromatic antioxidant, has characteristic peaks at m/z 268, 211, and 183 representative of the antiozonant and new peaks present at m/z 352, 288, 274, and 260. These latter three peaks are thought to represent the three molecular ions of the components of the antioxidant mixture in Goodyear s Wingstay 100, an aromatic amine antioxidant. 

Strohecker [97] has worked out a procedure for quantitative determination of ascorbyl palmitate in oils and fats he oxidises with 2,6-dichlorophenol-indophenol and treats the reaction product with 2,4-dinitrophenylhydrazine. The 2,4-dinitroosazone of ascorbic acid is formed under these conditions and may be easily separated from other compounds containing phenolic groups such as tocopherols. He uses a silica gel H layer and chloroform-ethyl acetate (50 + 50) for TLC. After development, the brick red zone of the osazone is scraped off and determined colorimetrically in solution m sulphuric acid. Down to 0.001% of ascorbyl palmitate in antioxidant mixtures and in oils and fats can be determined with this procedure. 

---