Antioxidant test procedures

The Antioxidant Test procedure for Superoxide is provided by the sup>pher of the test kit (Hipler and Knight, 2001). The amount of sample was optimised to obtain not more than 90% and typically 50% signal inhibition. This signal was then corrected for sample dilution 10 iL of sample was used, however, red wines and rose wines were first diluted with water (1 10) while white wines were not. 

Many methods are available for determining food antioxidant capacity, which is an important topic in food and nutrition research. However, there is a great need to standardize these methods because the frequent lack of an actual substrate in the procedure, the system composition, and the method of inducing oxidation could limit their accuracy. In fact, antioxidant activities in complex systems cannot be evaluated satisfactorily using a single test, and several test procedures may be required. The search for more specific assays that can be more directly related to oxidative deterioration of foods and biological systems should be the objective of future investigations. 

Since food additives are subjected to the most stringent toxicological testing procedures, only a few synthetic antioxidants have been used in foods for any length of time. Antioxidants are extensively tested for the absence of carcinogenity and other toxic effects in themselves, in their oxidised forms, and in their reaction products with food constituents, for their effectiveness at low concentrations, and for the absence of the ability to impart an unpleasant flavour to the food in which they are used. 

Let us now examine the antioxidant test results for the various phenols alkylated by a-olefins. They have been evaluated in several tests, but data are presented in Table III for only four different test procedures, chosen to illustrate the effect of increasing severity of test conditions. The least severe of these is the 140°C. stress-crack life test using a 65-mil thick molded bar. The 160 °C. oven-life test using the same molded bar is somewhat more severe. Increasing severity is shown by the 140°C. oven-life test and the 160°C. oven-life test using 5-mil film test pieces. The relatively thick bars used in the first two tests provide a reservoir of antioxidant to replace that lost from the surface. These tests probably measure the inherent effectiveness of the antioxidant. In the tests using... 

Methods of category (3) tract the capacity of the test compound to capture radicals or to inhibit radical formation rather than monitoring the actual oxidation product formation or substrate oxidation. Several new methods are developed based on this concept, and a variety of new parameters for expressing results are used. It is expected that a high correlation exists between these two types of measurements. It should be noted here that there are no standard units for reporting the antioxidant activity because such activity (assay, capacity, efficiency, effectiveness, etc.) is independent of the test procedure. Table 4 summarizes the methods available for measuring antioxidant activity and how the results of such determinations are expressed. 

Characterization of chemical additives such as antioxidants in plastics is often described as a daunting and challenging task. The need for complete compositional analysis of additive packages in industrial plastics for both research and quality control applications has led to the development of numerous analyte-specific test procedures in recent years. The methodology employed in these analyses must overcome many obstacles the relative instability and high reactivity of many types of additives, the residence of the additives in what is essentially an insoluble polymer material, and the relatively low concentration of these additives in the polymer matrix [1]. In addition, the analysis technique used must be specific and should not be susceptible to interference from other additives which may also be present in the polymer. 

Analysts in industry prefer in many cases to maintain consistent methods for their analyses. Recommended ASTM analytical procedures are quite well developed in the rubber and polymer industry. As an example, we mention the standard test method for determination of phenolic antioxidants and erucamide slip additives in LDPE using liquid chromatography [76]. However, the current industry standard test methods (ASTM, AOAC, IUPAC, etc.) use a large number of solvents in vast... 

The application should state the rationale for the design of the in-use stability tests performed. The procedures used should be fully validated. One key factor is that the test should simulate the use of the product as far as practicable. This should include any reconstitution or dilution prior to use. Aliquots should be removed in an appropriate manner following, as far as possible, the usage pattern that will be encountered in practice. Physical (color, clarity, closure integrity, particulate matter, and particulates/particle size), chemical (assays for active ingredient, antioxidants and... 

A technique for applying infrared measurements to insulating oil is available (ASTM D-2144), and considerable information about mineral oil composition can be gained from infrared spectroscopy. Oxygenated bodies formed when oil deteriorates can be recognized, and hence this procedure can be used for surveillance of oils in service. An infrared spectrum can also give information as to the aromaticity of an oil and can detect antioxidants such as 2,6 di-tertiary butyl p-cresol. A chemical test for the latter is, however, available and is preferable for quantitative purposes (ASTM D-1473). 

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