Extractability testing principles

Figure 20.3—Gas-svlid extraction. The principle of a gas-solid extraction column is shown as well as the chemical reaction used to derivatise an aldehyde in an atmospheric pollution test (adapted from a Supelco Inc. document). Examples of extraction tubes and a passive badge to trap gas samples are shown. (Reproduced by permission of Supelco Inc.. USA.)...

The test principle is such that the extraction of migratable substances from a sample of the plastics is determined as the mass of non-volatile residue after evaporation of the solvent following immersion. Test specimens of at least 1 dm2 (single side considered) are immersed in the extraction solvent at the specified test conditions and then... 

The difficulty in the dansyl chloride extraction test resides in the visual scoring of fluorescence extraction. Also, dansyl chloride has been shown to cause some cases of allergic reactions. For these two reasons, Pierard et al. [78] have proposed a variant to that test by using another skin surface marker, dihydroxyacetone which stains the skin in light brown. The principle of the test is exactly the same as above with the exception that dye extraction can, in this case, be measured instrumentally by using a reflectance colorimeter like the Minolta Chroma Meter . 

The principles covering the design of extraction tests proposed by various authorities are reviewed in Chapter 1. Chapters 2 and 3 review the types of polymers and elastomers, respectively, used in the packaging and the types of deliberately added or adventitious compounds that can occur in plastics and can be extracted into the packaged commodity. 

Ailanthus altissima (tree of heaven) grows in pure stands, hence, secretion of a toxic principle is implied. Mergen (98) prepared aqueous extracts of the foliage and found growth inhibition produced in 45 of 46 species of test plants. 

Subcase b2 This case, called the paired f-test , is often done when two test procedures, such as methods A and B, are applied to the same samples, for instance when validating a proposed procedure with respect to the accepted one. In practicular, an official content uniformity" 5 assay might prescribe a photometric measurement (extract the active principle from a tablet... 

The underlying problem in testing the validity of the additivity principle in corrosion, mineral extraction, and electroless plating is that the electrode metal itself forms part of one of the half-reactions involved, e.g., zinc in equation (5) and copper in equations (8) and (12). A much better test system is provided by the interaction of two couples at an inert metal electrode that does not form a chemical part of either couple. A good example is the heterogeneous catalysis by platinum or a similar inert metal of the reaction... 

For multi-analyte and/or multi-matrix methods, it is not possible to validate a method for all combinations of analyte, concentration and type of sample matrix that may be encountered in subsequent use of the method. On the other hand, the standards EN1528 andEN 12393 consist of a range of old multi-residue methods. The working principles of these methods are accepted not only in Europe, but all over the world. Most often these methods are based on extractions with acetone, acetonitrile, ethyl acetate or n-hexane. Subsequent cleanup steps are based on solvent partition steps and size exclusion or adsorption chromatography on Florisil, silica gel or alumina. Each solvent and each cleanup step has been successfully applied to hundreds of pesticides and tested in countless method validation studies. The selectivity and sensitivity of GC combined with electron capture, nitrogen-phosphorus, flame photometric or mass spectrometric detectors for a large number of pesticides are acceptable. 

Principles and Characteristics A first step in additive analysis is the identification of the matrix. In this respect the objective for most polymer analyses for R D purposes is merely the definition of the most appropriate extraction conditions (solvent choice), whereas in rubber or coatings analysis usually the simultaneous characterisation of the polymeric components and the additives is at stake. In fact, one of the most basic tests to carry out on a rubber sample is to determine the base polymer. Figure 2.1 shows the broad variety of additive containing polymeric matrices. 

Garlic supplements - powder tablets or capsules, steam-distilled oil, vegetable oil macerate extract, or extract aged in dilute alcohol - are widely available and are taken by millions. Since the active principle, allicin, is not present in garlic bulb, the supplements rely on the presence of precursor alliin and enzyme alliinase. In tests on 24 commercial brands of enteric-coated tablets, all except one gave low dissolution allicin release 83% of the brands released less than 15% of their potential allicin.78,79 Relevant factors were impaired enzyme activity caused by excipients and slow tablet disintegration. Caveat emptor ... 

Where neither defined active principles nor active markers are known, certain constituents of the botanical raw material and their extracts are chosen as candidates for quantitative determination. These markers aid in the positive identification of the article to be tested. In addition, maintaining a minimum content or a specified range of the analytical markers helps achieve standardization of the plant extract and arrive at suitable expiration date during stability studies. 

The principle behind the test method(s) is that antibodies are made of proteins that recognize and bind with foreign substances (antigens) that invade host animals. Synthetic antibodies have been developed to complex with petroleum constituents. The antibodies are immobilized on the walls of a special ceU or filter membrane. Water samples are added directly to the cell, while soils must be extracted before analysis. A known amount of labeled analyte (typically, an enzyme with an affinity for the antibody) is added after the sample. The sample analytes compete with the enzyme-labeled analytes for sites on the antibodies. After equilibrium is established, the cell is washed to remove any um-eacted sample or labeled enzyme. Color development reagents that react with the labeled enzyme are added. A solution that stops color development is added at a specified time, and the optical density (color intensity) is measured. Because the coloring agent reacts with the labeled enzyme, samples with high optical density contain low concentrations of analytes. Concentration is inversely proportional to optical density. 

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