Other Analytical Techniques

In addition to the analysis techniques discussed in Chapters 13 through 19, many other approaches, methods, and techniques are used to perform system safety analyses. 

Some of these different techniques actually represent new or unique approaches or methods. Others are variations of different names for common techniques. 

This chapter describes some of these techniques that may be of value in specific system safety efforts and those that the system safety practitioner is likely to encounter in system safety literature. 

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In comparison with most other analytical techniques, radiochemical methods are usually more expensive and require more time to complete an analysis. Radiochemical methods also are subject to significant safety concerns due to the analyst s potential exposure to high-energy radiation and the need to safely dispose of radioactive waste. 

Other analytical techniques ate also available for the determination of maleic anhydride sample purity. For example, maleic anhydride content can be determined by reacting it with a known excess of aniline [62-53-3] in an alcohol mixture (170). The solution is then titrated with an acid to determine the amount of unconsumed aniline. This number is then used to calculate the amount of maleic anhydride reacted and thus its concentration. Another method of a similar type has also been reported (171). 

The emitted P particles excite the organic molecules which, in returning to normal energy levels, emit light pulses that are detected by a photomultiplier tube, amplified, and electronically counted. Liquid scintillation counting is by far the most widely used technique in tritium tracer studies and has superseded most other analytical techniques for general use (70). 

The analytical techniques covered in this chapter are typically used to measure trace-level elemental or molecular contaminants or dopants on surfaces, in thin films or bulk materials, or at interfaces. Several are also capable of providing quantitative measurements of major and minor components, though other analytical techniques, such as XRF, RBS, and EPMA, are more commonly used because of their better accuracy and reproducibility. Eight of the analytical techniques covered in this chapter use mass spectrometry to detect the trace-level components, while the ninth uses optical emission. All the techniques are destructive, involving the removal of some material from the sample, but many different methods are employed to remove material and introduce it into the analyzer. 

LIMS analytical applications may be classifted as elemental or molecular survey analyses. The former can be further subdivided into surface or bulk analyses, while molecular analyses are generally applicable only to surface contamination. In the following descriptions of applications, a comparison with other analytical techniques is presented, along with a discussion of their relative merits. 

An especially significant application of NRA is the measurement of quantified hydrogen depth profiles, which is difficult using all but a few other analytical techniques. Hydrogen concentrations can be measured to a few tens or hundreds of parts per million (ppm) and with depth resolutions on the order of 10 nm. 

NRA is an effective technique for measuring depth profiles of light elements in solids. Its sensitivity and isotope-selective character make it ideal for isotopic tracer experiments. NRA is also capable of profiling hydrogen, which can be characterized by only a few other analytical techniques. Future prospects include further application of the technique in a wider range of fields, three-dimensional mapping with microbeams, and development of an easily accessible and comprehensive compilation of reaction cross sections. 

Quantitation in high performance liquid chromatography, as with other analytical techniques, involves the comparison of the intensity of response from an analyte ( peak height or area) in the sample under investigation with the intensity of response from known amounts of the analyte in standards measured under identical experimental conditions. 

The development of a quantitative method involving LC-MS is, in principle, no different from developing a quantitative method nsing any other analytical technique the intensity of signal from the analyte(s) of interest in the unknown sample is compared with that from known amounts of the analyte. The task of the analyst is to decide how this is best achieved knowing the resources available and the purpose for which the results are required. 

Where specific drugs have been demonstrated to Interfere with chemical reactions, patients should be maintained free of these drugs for at least 72 hours before collecting the specimen. Other analytical techniques, e.g. column chromatography and radioimmunoassay procedures, can also be substituted for an affected method. 

It should be pointed out that no other analytical technique has the capability to provide multi-element data non-destructively, often with good detection limits and... 

The advantages of immunoassay technology relative to other analytical techniques have been discussed in several reviews, and include the following ... 

Semiconductor chemical sensors are characterized by low cost, small size, extra high sensitivity (often unattainable in other analytical techniques) as well as reliability. Moreover, concentration of particles detected is being transformed directly into electrical signal and electronic design of the device is the simplest one which can be arranged for on the active part of the substrate. 

Marchetto, A., Mosello, R., Tartari, G. A., Muntau, H., Bianchi, M., Geiss, H., Serrini, G. and Fanza, G. S., Precision of ion chromatographic analyses compared with that of other analytical techniques through intercomparison exercises, /. Chromatogr. A, 706, 13, 1995. 

In an acetone extract from a neoprene/SBR hose compound, Lattimer et al. [92] distinguished dioctylph-thalate (m/z 390), di(r-octyl)diphenylamine (m/z 393), 1,3,5-tris(3,5-di-f-butyl-4-hydroxybenzyl)-isocyanurate m/z 783), hydrocarbon oil and a paraffin wax (numerous molecular ions in the m/z range of 200-500) by means of FD-MS. Since cross-linked rubbers are insoluble, more complex extraction procedures must be carried out (Chapter 2). The method of Dinsmore and Smith [257], or a modification thereof, is normally used. Mass spectrometry (and other analytical techniques) is then used to characterise the various rubber fractions. The mass-spectral identification of numerous antioxidants (hindered phenols and aromatic amines, e.g. phenyl-/ -naphthyl-amine, 6-dodecyl-2,2,4-trimethyl-l,2-dihydroquinoline, butylated bisphenol-A, HPPD, poly-TMDQ, di-(t-octyl)diphenylamine) in rubber extracts by means of direct probe EI-MS with programmed heating, has been reported [252]. The main problem reported consisted of the numerous ions arising from hydrocarbon oil in the recipe. In older work, mass spectrometry has been used to qualitatively identify volatile AOs in sheet samples of SBR and rubber-type vulcanisates after extraction of the polymer with acetone [51,246]. 

For the identification of mineral fillers in EPs, XRD was compared with various other analytical techniques (Table 8.55). Both IR and XRF allowed identification... 

The main advantages of plasma-source mass spectrometry (PS-MS) over other analytical techniques, such as PS-AES and ETAAS, are the possibilities of quantitative isotope determination and isotope dilution analysis the rapid spectral scanning capability of the mass spectrometer and semiquantitative determinations to within a factor of two or three. Several labelling methods are used for the quantification of analytes present in complex mixtures. In these methods, the sample is spiked... 

Activation analysis is based on a principle different from that of other analytical techniques, and is subject to other types of systematic error. Although other analytical techniques can compete with NAA in terms of sensitivity, selectivity, and multi-element capability, its potential for blank-free, matrix-independent multielement determination makes it an excellent reference technique. NAA has been used for validation of XRF and TXRF. 

Groundwater models and other analytic techniques are available to assist in proper pump siting, choosing pump capacities, and calculating the movement of the contaminant plume. The characteristics of the aquifer, the flow of groundwater, and the size of the plume should be known. 

The first thing to understand about NMR is just how insensitive it is compared with many other analytical techniques. This is because of the origin of the NMR signal itself. 

This is the easiest case for NMR (and other analytical techniques). What we are looking for is the relative proportion of compounds in a mixture. To do this, we identify a signal in one compound and a signal in the other. We then normalise these signals for the number of protons that they represent and perform a simple ratio calculation. This gives us the molar ratio of the two compounds. If we know the structure (or the molecular weight) of these compounds, then we can calculate their mass ratio. 

CL as an analytical tool has several advantages over other analytical techniques that involve light (mainly absorption spectroscopy and fluorometry) high detectability, high selectivity, wide dynamic range, and relatively inexpensive instrumentation. 

Identification of the component peaks of a chromatogram, which may be numerous, can be achieved in two ways comparison of retention times (discussed below) trapping the eluted components for further analysis by other analytical techniques such as infrared and mass spectrometry or by direct interfacing of these techniques with a gas chromatograph. This latter approach is discussed on p. 114. 

Combination of Gas Chromatography with Other Analytical Techniques... 

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