Fingerprinting Materials

Fingerprinting materials, identification of bulk additives such as plasticisers and fillers. Non-destructive examination of samples... 

Infrared (IR) spectroscopy is commonly used to "fingerprint" materials by comparing the IR absorption spectra of unknowns against reference standards. 

Fingerprinting materials using valence band spectra... 

Cleaning, the removal of unwanted matter, is the beginning of the treatment cycle for metal. The unwanted matter may be carbon smut, welding flux, ink, oxidation products, oil, fingerprints, or other material. Cleaners may be classified as solvent-based or aqueous. Within the aqueous class there are many subclasses, the most important of which are the alkaline cleaners. There are also a variety of ways to apply cleaners. As of the mid-1990s, solvent-based cleaner usage is declining. 

One of the most common modes of characterization involves the determination of a material s surface chemistry. This is accomplished via interpretation of the fiag-mentation pattern in the static SIMS mass spectrum. This fingerprint yields a great deal of information about a sample s outer chemical nature, including the relative degree of unsaturation, the presence or absence of aromatic groups, and branching. In addition to the chemical information, the mass spectrum also provides data about any surface impurities or contaminants. 

A recent application of this type of fluid is assistance in the removal of ingested salt spray from jet aircraft compressors and the neutralisation of corrosive effects. Other types of water-displacing fluids are claimed to have fingerprint neutralising properties or to be suitable for use on electrical equipment. Some oil-type materials serve temporarily as engine lubricants and contain suitable inhibitors to combat the corrosive products of combustion encountered in gasoline engines. 

In the powder diffraction technique, a monochromatic (single-frequency) beam of x-rays is directed at a powdered sample spread on a support, and the diffraction intensity is measured as the detector is moved to different angles (Fig. 1). The pattern obtained is characteristic of the material in the sample, and it can be identified by comparison with a database of patterns. In effect, powder x-ray diffraction takes a fingerprint of the sample. It can also be used to identify the size and shape of the unit cell by measuring the spacing of the lines in the diffraction pattern. The central equation for analyzing the results of a powder diffraction experiment is the Bragg equation... 

Rycroft et al. (1999) identihed the major components of plants from six locations in western Scotland and four from the Azores using nuclear magnetic resonance (NMR) fingerprinting and GC-MS. The terpene P-phellandrene [129], which may be responsible for the aroma of material crushed in the held, was detected in all specimens. The major components, which appear in Fig. 5.6, were shown to be methyl eveminate [444], the four methyl orcellinate derivatives [445 8], the two 9,10-dihydrophenanthrene derivatives [449] and [450], the newly described phthalide killamiensolide [451], and the bibenzyl [453]. Methyl eveminate was the major compound in all 10 specimens other compounds were more varied in their occurrence. Killamiensolide was not isolated as such but was detected when extracts were acetylated yielding, among other compounds, [452]. The presence of the bibenzyl compound [453] in more than trace amounts in P. killarniensis raises the possibility that it represents contamination from P. spinulosa with which it was growing at the one site. 

Fig. 2e), virtually absent in perfect siUcalite-1 and immediately identified as a fingerprint of TS-1 material [37,52-55,63,70,71]. A qualitative correlation between the intensity of the infrared band at 960 cm and Ti content has been observed since the first synthesis of TS-1. Indeed, the occurrence of that band is one of the distinctive features of the material cited in the original patent [7]. However, the quantitative correlation has been reported only very recently by Ricchiardi et al. [52], owing to very serious experimental problems related to the saturation of the IR framework modes, hi the same work, the nature of the 960 cm band has been discussed in terms of theoretical calculations based on both cluster and periodical approaches. 

There have been a number of attempts to achieve this objective, but so far the challenge has not been fully met. This Chapter will examine some of the conventional approaches and then go on to consider how recent developments in the use of the Polymerase Chain Reaction (PCR) with DNA for the identification of species and individual organisms by DNA analysis, sometimes known as DNA Fingerprinting", have identified a yet unrealized need for a new dimension of certified reference materials. 

It is equally important for the manufacturer and regulator to know the level of additives in a polymer material to ensure that the product is fit for its intended purpose. Additive analysis marks sources of supply, provides a (total) process signature and may actually be used as a fingerprint of a polymeric material, in particular as molecular characterisation of the polymer... 

Ehret-Henry et al. [220] have shown that H NMR spectra can be used without chromatographic analysis, to shorten the total identification time necessary, and as a fingerprint of all the extractable nonvolatile compounds present in food packaging material (safety control). Figure 5.10 shows a H NMR spectrum (in CDCI3 with TMS as internal standard) of a Soxhlet extract of a 35 pirn PP film (after solvent evaporation). The assignments of the resonances of Irgafos 168 and its decomposition products were confirmed by a 31P- H 2D correlation NMR experiment [220],... 

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