Injection antioxidants

FIGURE 31,14 (a) Schematic diagram of an FI system with the electrochemical detection of online generation of ABTS +. (b) Construction of a flow-through electrochemical detector, (c) FI signals obtained for water-soluble AOXs. The concentration of injected antioxidant solutions 250 pM for Tr, Asc, and uric acid 220 pM for reduced glutathione. (Modified from Milardovic, S., I. Kerekovic, and V. Rumenjak. 2007. Food Chem. 105 1688-1694.)... 

Labrinea, E. P. and C. A. Georgiou. 2005. Rapid, fully automated flow injection antioxidant capacity assay. J. Agric. Food Chem. 53 4341-4346. 

Processing. SAN copolymers may be processed using the conventional fabrication methods of extmsion, blow mol ding, injection molding, thermoforming, and casting. Small amounts of additives, such as antioxidants, lubricants, and colorants, may also be used. Typical temperature profiles for injection mol ding and extmsion of predried SAN resins are as follows (101). 

The three classes of PE, designated as A, B, and C, specify the color, amount, and type of antioxidants and other additives. Class A refers to naturally colored PE, Class B includes white or black polymer, and Class C covers weather-resistant black polymer containing no less than 2% carbon black. Typical characteristics of resins used for film manufacture, injection mol ding, and blow mol ding are given in Table 5. 

Dicyclopentadiene is also polymerized with tungsten-based catalysts. Because the polymerization reaction produces heavily cross-Unked resins, the polymers are manufactured in a reaction injection mol ding (RIM) process, in which all catalyst components and resin modifiers are slurried in two batches of the monomer. The first batch contains the catalyst (a mixture of WCl and WOCl, nonylphenol, acetylacetone, additives, and fillers the second batch contains the co-catalyst (a combination of an alkyl aluminum compound and a Lewis base such as ether), antioxidants, and elastomeric fillers (qv) for better moldabihty (50). Mixing two Uquids in a mold results in a rapid polymerization reaction. Its rate is controlled by the ratio between the co-catalyst and the Lewis base. Depending on the catalyst composition, solidification time of the reaction mixture can vary from two seconds to an hour. Similar catalyst systems are used for polymerization of norbomene and for norbomene copolymerization with ethyhdenenorbomene. 

As the above mentioned studies with high supplementation dosages exemplarily show, there is no known toxicity for phylloquinone (vitamin Kl), although allergic reactions are possible. This is NOT true for menadione (vitamin K3) that can interfere with glutathione, a natural antioxidant, resulting in oxidative stress and cell membrane damage. Injections of menadione in infants led to jaundice and hemolytic anemia and therefore should not be used for the treatment of vitamin K deficiency. 

Epinephrine is an inherently unstable chemical in aqueous solution, even at a low pH and in the presence of an antioxidant such as sodium metabisulfite, up to 1 mg/ ml. With the passage of time, the epinephrine dose gradually decreases due to degradation into inactive compounds. If the expiry date has passed, the epinephrine dose correlates inversely with the number of months or years past that date, and will likely be lower than the dose stated on the label even if the solution appears clear and colorless. Nevertheless, if this is the only source of epinephrine available for injection, it should be used in preference to not administering epinephrine at all [32]. 

David et al. [184] have shown that cool on-column injection and the use of deactivated thermally stable columns in CGC-FID and CGC-F1D-MS for quantitative determination of additives (antistatics, antifogging agents, UV and light stabilisers, antioxidants, etc.) in mixtures prevents thermal degradation of high-MW compounds. Perkins et al. [101] have reported development of an analysis method for 100 ppm polymer additives in a 500 p,L SEC fraction in DCM by means of at-column GC (total elution time 27 min repeatability 3-7 %). Requirements for the method were (i) on-line (ii) use of whole fraction (LVI) and (iii) determination of high-MW compounds (1200 Da) at low concentrations. Difficult matrix introduction (DMI) and selective extraction can be used for GC analysis of silicone oil contamination in paints and other complex analytical problems. 

C12 to C20, primarily Ci6 to ( is), used as surface lubricants in the manufacture of food-contact articles. The method, which uses ethyl palmitate (Eastman Chemicals No. 1575 Red Label) as an internal standard, has been validated at 200 ppm total FAME [185]. Other FAME standards (methyl palmitate, methyl stearate, methyl oleate, methyl linoleate and methyl linolenate) are available (Applied Science Laboratories) [116], Worked out examples of additive determinations are given in the Food Additives Analytical Manual [116], which also describes a great many of indirect food additives, such as BHA, BHT, TBHQ, l-chloro-2-propanol, DLTDP, fatty acid methyl esters, w-heptyl-p-hydroxybenzoate, propyl-gallate, sodium benzoate, sodium stearoyl-2-lactylate, sorbitol and phenolic antioxidants. EPA methods 606 and 8060 describe the CGC separation of phthalate esters (direct injection) (cf. Figure 4.2). 

Figure 4.25 Overlay of 12 injections of antioxidant standards gradient elution, UV detection at 230 nm. After Alden and Woodman [829]. Reproduced by permission of the authors...

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. 

Why do the resins used in rotational molding processes typically contain a higher level of antioxidants and thermal stabilizers than the resins used to manufacture parts, by injection molding ... 

Figures 10 and 11 show the structure of the hindered phenolic antioxidant Irganox 1010 (Ciba) and its negative ion APCI mass spectra, respectively. Separation was achieved under the following LC conditions Column Aqua Cl 8 (Phenomenex) 3 pm, 150x2.00 mm, 15% carbon loading, proprietary end capping. Column Temp 50°C. Injection volume 5 pi.

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).

Inhibitors can be injected into the system in order to kill active species present, for example, by neutralizing the catalyst or by capturing free radicals in a polymerization. For example, the Lewis acid, BF3-complex can be killed using gaseous NH3 since the inactive compound BF3 NH3 is formed, and the reaction stops for lack of active centers. An antioxidant such as hydroquinone can be used to capture peroxide radicals to control reactions involving vinyl-type monomeric substances. 

Parenterais The most important criterion for parenterals is that they have to be sterile for injection or infusion administration. Excipients are added to make parenterals isotonic with blood, improve solubility, and control pH of the solution. The solvent vehicles include water-for-injection, sterile sodium chloride, potassium chloride, or calcium chloride solution, and nonaqueous solvents such as alcohol, glycol, and glycerin. Preservatives, antioxidants, and stabilizers are normally added to enhance the properties of the drug product. 

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