Analytical tests

Analytical tests are important to material suppliers and processors. These tests provide basic information that is necessary for characterizing and qualifying the material. Analytical tests such as density and specific gravity tests are used as a 

Unlike metals and ceramics, plastics absorb water. The amount of water absorption depends upon the specific type of plastic. The key properties—mechanical, electrical, and optical—are seriously affected. Water also tends to act as a plasticizer and lowers the softening temperature of the part (1). Plastic materials that absorb a large amount of water normally affect the dimensional stability of the product. The plastic product designer must take into account the water absorption characteristics of the plastic materials to avoid premature failures. 

Another important and frequently used test throughout the industry is the moisture analysis test. This simple but effective test provides useful information regarding the processibility of plastic materials. Excessive moisture can cause many processing and visual problems such as splay marks. Bulk density tests and sieve analysis tests also help to predict the material s behavior during mixing, compounding, and processing. Chapter 7 discusses analytical tests often used in material characterization. 

Handbook of Plastics Testing and Failure Analysis, Third Edition, by Vishu Shah Copyright 2007 by John Wiley Sons, Inc. 

Specific gravity is defined as the ratio of the weight of the given volume of a material to that of an equal volume of water at a stated temperature. The temperature selected for determining the specific gravity of plastic parts is 23°C. 

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The haloform reaction using iodine was once used as an analytical test in which the formation of a yellow precipitate of iodoform was taken as evidence that a substance... 

A laboratory wishing to register under the CLP must perform certain analytical test procedures to the EPA s satisfaction. 

The objective of the FCC is to define food-grade chemicals in terms of the characteristics that estabUsh identity, strength, and quahty. It provides specifications in monograph form for some 900 food additives, together with analytical test procedures by which compliance with the specifications can be determined. The third edition was pubUshed in 1981 supplements followed in 1983, 1986, 1991, and 1993. The fourth edition is in preparation as of this writing and is to include monographs for almost 1000 food chemicals, including flavors. 

Analyses and Analytical Test Methods for P4SJQ. A typical analysis of P S q yields the following. 

Tables 16 and 17 Hst tke analytical test methods for different properties of interest. The Manufacturing Chemists Association, Inc. (MCA) has pubUshed the Chemical Safety Data Sheet SD 63, which describes in detail procedures for safe handling of use of toluene (46). The Interstate Commerce Commission classifies toluene as a flammable Hquid. Accordingly, it must be packaged in authorized containers, and shipping must comply with ICC regulations. Properties related to safe handling are autoignition temperature, 536°C explosive limits, 1.27—7.0 vol % in air and flash point 4.4°C, closed cup.

Although simple analytical tests often provide the needed information regarding a water sample, such as the formation and presence of chloroform and other organohaUdes in drinking water, require some very speciali2ed methods of analysis. The separation of trace metals into total and uncomplexed species also requires special sample handling and analysis (12). 

Table 5. Special Analytical Test Methods for Carbon Black...

Various analytical tests determine zeolite properties. These tests supply information about the strength, type, number, and distribution of acid sites. Additional tests can also provide information about surface area and pore size distribution. The three most common parameters governing zeolite behavior are as follows ... 

American Society of Testing and Materials (ASTM) is the organization that develops analytical tests and procedures to facilitate commerce. 

Table 15.9 Analytical tests on industrial phosphate coatings...

Analytical Tests for Nitriles (Ref 6J. 1) Redn to the corresponding amines with Na ale identifying the amines by the usual methods ... 

Product specification documents and analytical test methods—In preclinical development, these are important documents and they evolve along with the development phases. Drug substances and products for clinical trials are tested based on these documents, and so are the stability samples. It is critical to ensure that the analyst will perform the right tests against the right specifications with the correct version of the test method. Therefore a mechanism must be in place to control these documents. This can be done manually or with TIMS. A manually controlled system would require the analyst to sign out hard copies of the documents from a central location. After the testing is done, the analyst would have to return these controlled documents to the... 

BASF, Analytical Tests for the Sicovit and Sicomed Colorants, Technical Information, 8, 1996. 

In feature selection one selects from the m variables a subset of variables that seem to be the most discriminating. Feature selection therefore constitutes a means of choosing sets of optimally discriminating variables and, if these variables are the results of analytical tests, this consists, in fact, of the selection of an optimal combination of analytical tests or procedures. 

Direct and indirect competition formats, illustrated in Figure 1, are widely used for both qualitative and quantitative immunoassays. Direct competition immunoassays employ wells, tubes, beads, or membranes (supports) on to which antibodies have been coated and in which proteins such as bovine semm albumin, fish gelatin, or powdered milk have blocked nonspecific binding sites. Solutions containing analyte (test solution) and an analyte-enzyme conjugate are added, and the analyte and antibody are allowed to compete for the antibody binding sites. The system is washed, and enzyme substrates that are converted to a chromophore or fluorophore by the enzyme-tracer complex are added. Subsequent color or fluorescence development is inversely proportionate to the analyte concentration in the test solution. For this assay format, the proper orientation of the coated antibody is important, and anti-host IgG or protein A or protein G has been utilized to orient the antibody. Immunoassays developed for commercial purposes generally employ direct competition formats because of their simplicity and short assay times. The price for simplicity and short assay time is more complex development needed for a satisfactory incorporation of the label into the antibody or analyte without loss of sensitivity. 

Reports by the National Canners Association showed negative results on both taste tests and analytical tests for residual chlorides. Asparagus treated and canned in a manner comparable to the celery also gave completely negative results. 

The premarket notification application, 510(k), is reviewed by the FDA scientific staff. This evaluation takes into consideration tumor-associated analytes, test requirements, medical usefulness of the test system for a particular clinical claim, and its application (i.e., monitoring or treatment follow-up). The FDA determines the appropriate performance requirements for each tumor analyte category. The agency s staff considers factors, such as consequences of a false positive or false negative, and the importance or impact of an absolute versus a significant change in the results or values of the tumor marker tests. The performance criteria (parameters) of a particular tumor marker test are compared with those of previously... 

Both qualitative observations and quantitative measurements cannot be reproduced with absolute reliability. By reason of inevitable deviations, measured results vary within certain intervals and observations, mostly in form of decision tests, may fail. The reliability of analytical tests depends on the sample or the process to be controlled and the amount of the analyte, as well as on the analytical method applied and on the economical expenditure available. 

If an analytical test results in a lower value x, < x0, then the customer may reject the product as to be defective. Due to the variation in the results of analyses and their evaluation by means of statistical tests, however, a product of good quality may be rejected or a defective product may be approved according to the facts shown in Table 4.2 (see Sect. 4.3.1). Therefore, manufacturer and customer have to agree upon statistical limits (critical values) which minimize false-negative decisions (errors of the first kind which characterize the manufacturer risk) and false-positive decisions (errors of the second kind which represent the customer risk) as well as test expenditure. In principle, analytical precision and statistical security can be increased almost to an unlimited extent but this would be reflected by high costs for both manufacturers and customers. 

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