Peroxide Value Limit Test

Rancidity measurements are taken by determining the concentration of either the intermediate compounds, or the more stable end products. Peroxide values (PV), thiobarbituric acid (TBA) test, fatty acid analysis, GC volatile analysis, active oxygen method (AOM), and sensory analysis are just some of the methods currently used for this purpose. Peroxide values and TBA tests are two very common rancidity tests however, the actual point of rancidity is discretionary. Determinations based on intermediate compounds (PV) are limited because the same value can represent two different points on the rancidity curve, thus making interpretations difficult. For example, a low PV can represent a sample just starting to become rancid, as well as a sample that has developed an extreme rancid characteristic. The TBA test has similar limitations, in that TBA values are typically quadratic with increasing oxidation. Due to the stability of some of the end-products, headspace GC is a fast and reliable method for oxidation measurement. Headspace techniques include static, dynamic and solid-phase microextraction (SPME) methods. Hexanal, which is the end-product formed from the oxidation of Q-6 unsaturated fatty acids (linoleate), is often found to be a major compound in the volatile profile of food products, and is often chosen as an indicator of oxidation in meals, especially during the early oxidative changes (Shahidi, 1994). 

Lead Determine as directed for Method II in the Atomic Absorption Spectrophotometric Graphite Furnace Method under Lead Limit Test, Appendix IDB, using a 5-g sample. Peroxide Value Determine as directed in Method II under Peroxide Value, Appendix VII. 

To limit the total porosity of the coating, checking by the Iron Solution Value (ISV) test in which samples are immersed under standard conditions in a solution of sulphuric acid, hydrogen peroxide and ammonium thiocyanate, and the amount of iron dissolved is measured... 

Numerous specifications and control measures are employed to determine final product quality, the first of which is ensuring adequate quality of excipients and active ingredients. Excipient testing ensures compliance with compendial specifications, as well as specifications determined during development of the fill material and/ or shell formulation. Among these are limiting values for trace impurities, especially peroxides, aldehydes, some metals, and ionic salts. 

At all events, however, it will be reasonable, in practice, to consider a temperature 30 K lower than the value of the BAM test calculated herein for an organic liquid peroxide as the upper limit temperature for the safe handling of the peroxide. For instance, -10 °C will be the upper limit temperature for the safe handling of THPN, 10 °C for BPOD, 20 °C for TPIC, and so forth. 

The identification of those variables that have a major effect on plutonium peroxide precipitation was done in two ways. The first way used t-test values associated with each variable. The comparative magnitude of these values indicates the relative importance of the variable. The second way involved a subjective evaluation of the relative importance of each of the variables based on a visual comparison of the graphs constructed from the experimental data (Figures 1 through 12 plus a couple of dozen other comparable graphs that could not be included in this paper because of space limitations). The results of the subjective evaluation indicate that only the nitric acid concentration and the rate of hydrogen peroxide addition have a major effect on the relative filtration time. The other four variables influence the... 

The difficulty results, in part, from the fact that only a small fraction of the chemical bonds, generally less than one in a thousand, are involved in me-chanochemical processes. The concentration of connecting units is therefore at the detection limit and below for traditional analytical methods such as conventional nuclear magnetic resonance and infrared spectroscopy. The sensitivity can, of course, be enhanced by techniques such as cumulative, multiple scans, Fourier transform analysis, and difference techniques for detection to one part in ten thousand and better. It may yet be difficult to determine whether polymers are linked by chemical bonds or whether they are simply intimate mixtures. For this distinction, other tests can be of value. For example, the difference between blocks and blends for ethylene-propylene polymer systems has been distinguished by thermal analysis [5]. In many cases, simple extraction tests can distinguish between copolymers and blends. For example, for rubber milled into polystyrene, the fraction of extractable rubber is a measure of mechanochemistry. Conversely, only the rubber in this system is readily cross-linked by benzoyl peroxide after which free polystyrene may be conveniently extracted [6]. In another case, homopolymers of styrene and methyl methacrylate can be separated cleanly from each other and from their copolymers by fractional precipitation [7]. The success of such processes, of course, depends on both the compositions and molecular weights involved. 

An extensive literature on the examination of ether includes little on quantitative measurement of the impurities present, tests being devised mainly as limiting values. The impurities commonly present are water, ethanol, methyl ether, free acid, aldehyde, acetone and peroxides. The first four compounds are present from manufacture and the last three are formed by decomposition. Water and ethanol are not serious impurities and determine its weight per millilitre. 

Due to the inherent danger of peroxides in butadiene, specification limits are usually set for their presence. This test method will provide values that can be used to determine the peroxide content of a sample of commercial butadiene. 

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