Elemental organic microanalysis

For such light elements, atomic absorption spectroscopy (unusable due to a lack of suitable sources) or of X-ray fluorescence spectroscopy (lack of sensitivity due to radiation of low energy) are inappropriate. 

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Elemental organic microanalysis is one of the main methods for purity verification of organic and organoelement compounds and polymers. 

E. Pella, Elemental Organic Microanalysis Yesterday and Today, Short Notes, Carlo Erba Strumentazione, Milan, 1978. 

Microanalysis, the detection and identification of materials present in small size but relatively high concentration, is distinct from trace analysis, which is concerned with the characterization of small concentrations of material. Organic microanalysis is usually taken to mean elemental analysis (primarily C, H, O, N, P, S, Cl, Br, 1, and Si), and functional group analysis (acetyl, carboxyl, benzoyl, amino, nitro, hydroxy, etc.) on samples usually 1-10 mg in size. The semiquantitative results, accurate to about 10%, serve as a measure of impurities, or inhomogeneity, or for structure determination in solid organic substances. Accurate results of 1 % or better may be expected when large (1 g) samples are taken for analysis and the entire chemical apparatus is scaled upward in size. However, small samples take less time to analyze, so the micro methods are more popular than macro methods. 

LIMS is primarily used in failure microanalysis applications, which make use of its survey capability, and its high sensitivity toward essentially all elements in the periodic table. The ability to provide organic molecular information on a microanalyt-ical scale is another distinctive feature of LIMS, one that is likely to become more important in the future, with improved knowledge of laser desorption and ionization mechanisms. 

The simplest formula for an organic compound is called its empirical formula. This shows the elements present in the compound and the simplest ratio of the atoms of these elements in the compound. For example, ethane (C H ) has an empirical formula of CHj, whereas benzene (C H ) has an empirical formula of CH. Empirical formulae can be determined by a technique known as elemental microanalysis and you will find out more about this on p. 72. 

A number of experimental techniques are carried out in organic chemistry to confirm that the correct compound has been synthesised during a reaction, or to identify unknown compounds. Some of these techniques are laboratory-based and are discussed in the Researching Chemistry section. Organic chemists rely heavily on a number of other techniques to identify compounds. These include elemental microanalysis, mass spectrometry, infrared spectrometry and NMR spectrometry. 

Elemental microanalysis is used to determine the masses of the elements present in a sample of an organic compound to work out its empirical formula. 

Elemental microanalysis (or combustion analysis) can be used to determine the empirical formula of an organic compound. 

ANALYSIS (Organic Chemical). Various techniques are used in the chemical analysis of organic substances both in microanalysis and macro laboratory procedures. As contrasted with the determination of total carbon content or the amounts of other specific chemical elements, the representative analytical techniques described here are directed toward the determination of presence and amount of various functional groups (radicals). These groups also are described elsewhere in this volume and, in several instances, additional analytical procedures are related. 

Characterization of polymers 5-9 was achieved by XH and 31P NMR spectroscopy, gel permeation chromatography, differential scanning calorimetry, UV/visible and infrared spectroscopy, and elemental microanalysis. All the polymers were soluble in common organic media, such as tetrahydrofuran, acetone, and methylethyl ketone. 

Muir, M.D., Spicer, R.A., Grant, P.R. and Giddens, R., 1974. X-ray microanalysis in the SEM for the determination of elements in modern and fossil micro-organisms. In J.V. Sanders and D.J. Goodchild (Editors), Electron Microscopy 1974, Vol. II Biological, 8th International Congress on Electron Microscopy, Canberra, The Australian Academy of Science, Canberra, pp. 104—105. 

Ingram, G. (1962). Methods of Organic Elemental Microanalysis. Reinhold, New York. 

G. Ingram,Afef/jods of Organic Elemental Microanalysis, Chapman and Hall, London, 1962. 

Material properties often depend on the constituents of inclusions as small as a few micrometers large or surface layers with a thickness of 0.1-100 nm. From the 1970s onward, microanalysis has become a major challenge. Initial methods such as electron probe X-ray microanalysis (EPXMA) or dynamic secondary ion mass spectrometry (SIMS) determine elements at the microscopic scale, but charge buildup and beam-induced sample damage hamper their application to nonconducting organic materials. 

TOF-SIMS Hme-of-flight SIMS Surface microanalysis of organic/molecular and elemental species Secondary ions and molecules [Pg.152]

Many of the preparations noted for SEM and TEM also can cause artifacts for microanalysis in these same instruments. Note the various factors in Table 7.8 that describe the details and limits of energy and wavelength dispersive microanalysis. Contamination can cause problems, especially in the case of light element analysis. The source of foreign material is usually organic material on the specimen surface or in the vacuum system. The polymer microscopist has the added difficulty of working with polymers that are often the source of the contamination as the electron beam damages... 

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