Destructive methods

A new, non destructive method has been developed for testing high strength bolts which is based on measuring the magnetic stress on the head of a bolt. The forces originating in the body of the bolt can be determined in this way since these forces are proportional to the stress state in the head of the bolt. 

Oxides (Ln Oj), fluorides (LnF ), sulfides (Ln S, LnS), sulfofluorides (LnSF) of lanthanides are bases of different functional materials. Analytical control of such materials must include non-destructive methods for the identification of compound s chemical forms and quantitative detenuination methods which does not require analytical standards. The main difficulties of this analysis by chemical methods are that it is necessary to transform weakly soluble samples in solution. 

The thickness of the absorbent on the TLC plates could be between 0.2mm to 2mm or more. In preparative work, the thicker plates are used and hundreds of milligrams of mixtures can be purified conveniently and quickly. The spots or areas are easily scraped off the plates and the desired substances extracted from the absorbent with the required solvent. For preparative TLC, non destructive methods for visualising spots and fractions are required. As such, the use of UV light is very useful. If substances are not UV active, then a small section of the plate (usually the right or left edge of the plate) is sprayed with a visualising agent while the remainder of the plate is kept covered. 

This is a destructive method in which the resin is ground and pelleted as a KBr disc and analysed by FT-IR analysis. This method works best for systems where disdnct ftinctional group transformations (C=0, C-OH, C=C, etc) are expected. No special equipment is needed. 

Destruction methods, including incineration and biological gas purification... 

The technologies used in the control of gaseous organic compound emissions include destruction methods such as thermal and catalytic incineration and biological gas treatment and recovery methods such as adsorption, absorption, condensation, and membrane separation. The most common control methods are incineration, adsorption, and condensation, as they deal with a wide variety of emissions of organic compounds. The most common types of control equipment are thermal and fixed-bed catalytic incinerators with recuperative heat recovery, fixed-bed adsorbers, and surface condensers. The control efficiencies normally range between 90% and 99%. 

Another destructive method for the deterrmnation of organic fluonne is oxygen-flask combustion [3, 16, 17]... 

Crystalline material will diffract a beam of X-rays, and X-ray powder diffractometry can be used to identify components of mixtures. These X-ray procedures are examples of non-destructive methods of analysis. 

Some information relevant to the choice of appropriate methods is given in condensed form in Table 1.1, which is divided into three sections the classical techniques a selection of instrumental methods some non-destructive methods. 

It must be stressed, however, that the whole object may be the analytical sample, e.g. a specimen of moon-rock. Ideally this sample would be analysed by non-destructive methods. Occasionally the bulk material may be homogeneous (some water samples) and then only one increment may be needed to determine the properties of the bulk. This increment should be of suitable size to provide samples for replicate analyses. 

For this particular product, in addition to a decrease in analysis time, a non-destructive method is especially desirable because of other physical tests that are also required on each sample By FNAA, the total nitrogen content of a sample is first detd and then related to compn of the mixture. Since Octols contain no ingredients other than pure TNT (18.50% N) and pure HMX (37.84%), the following linear relationship is derived from the ealed nitrogen content of each ingredient ... 

Various destructive and non-destructive methods of analysis have been tested and H-l and C-13 NMR have, among other techniques provided valuable structural information on soluble humic acids and fulvic acids 48, Humin, on the other hand has withstood detailed non-destructive analysis. 

The first option is to improve the calcination process, usually by a two-step calcination. Other different mild template-destructive methods have been proposed. 

All the analytical methods mentioned to separate, identify, and quantify chlorophylls and derivatives consume time, money, and samples. As alternatives, industries have been employing non-destructive methods for surface color measurements that are not only indirectly related to chlorophyll content, but may also estimate the pigments directly in tissues, leaving the sample intact and enabling serial analyses in a relatively short time. Eood color affects consumer acceptance and is an important criterion for quality control. Color vision is a complex phenomenon that depends on both the total content and number of pigments and also on absorption, reflectance and emission spectra of each compound present. 

Analytical techniques for the quantitative determination of additives in polymers generally fall into two classes indirect (or destructive) and direct (or nondestructive). Destructive methods require an irreversible alteration to the sample so that the additive can be removed from the plastic material for subsequent detention. This chapter separates the additive wheat from the polymer chaff , and deals with sample preparation techniques for indirect analysis. 

The use of differential UV spectroscopy is a facile analytical tool, providing a rapid, non-destructive method for determining the course and extent of degradation of PC films during accelerated or natural weathering. 

Dinkelaker B., Hahn G., Romheld V., Wolf G.A, Marschner H. Non-destructive methods for demonstrating chemical changes in the rhizosphere 1. Description of method. Plant Soil 1993 155/156 67-70. 

A fourth technique used for the characterization of molecules is mass spectrometry. It is included in this chapter because the structural information it provides is similar to that obtained from the other techniques although the principle is entirely different. It is a destructive method in which the fragmentation pattern of sample molecules is used to determine empirical formulae and molecular weights, and to identify structural features. 

It is obvious that the simpler a method of analysis, the easier it will be to automate. Non-destructive methods which involve a minimum of sample treatment are the most attractive. X-ray fluorescence, for example, has been successfully applied to the continuous monitoring and control of process streams. However, the scope of automated analysis is wide and methods have been designed with a basis in nonspecific properties (pH, conductance, viscosity, density) as well as those characteristic of the che-... 

There is constant development and change in the techniques and methods of analytical chemistry. Better instrument design and a fuller understanding of the mechanics of analytical processes enable steady improvements to be made in sensitivity, precision, and accuracy. These same changes contribute to more economic analysis as they frequently lead to the elimination of time-consuming separation steps. The ultimate development in this direction is a non-destructive method, which not only saves time but leaves the sample unchanged for further examination or processing. 

Destructive methods, often called pyrolysis, are also used to determine components in soil. This commonly involves heating soil to a high temperature and analyzing the components given off. Often, analysis is by GC, mass spectrometry, or a combination of the two, although spectroscopic analysis is also possible [16]. 

The aspects which relate to the homogeneity of the sample have to be considered in the context of the nature of the analytical process. Also the nature of the analytical process is determined by the characteristics of the sample to be analysed. Hence the two groups of analytical methods, destructive and non-destructive, should be considered separately. Although both groups have wide applicability, the analytical chemist has a tendency to prefer the non-destructive methods. Since such methods act directly upon the sample, they have the advantage of partly—and with some precautions, totally—eliminating the risk of contamination of the sample. 

The choice of one or other of the methods depends on the nature of the sample. Generally, the non-destructive methods are applied to samples with relatively simple composition. However, for more complex samples or when the determination of major and minor components is required, preliminary separation of the components and concentration of the minor or trace components are necessary, before the actual determination may be performed. It follows therefore, that the analytical chemist must resort in many cases, willingly or not, to destructive methods of analysis. 

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