Atomic spectroscopy elements requiring quantification

The selection of a technique to determine the concentration of a given element is often based on the availability of the instrumentation and the personal preferences of the analytical chemist. As a general rule, AAS is preferred when quantifications of only a few elements are required since it is easy to operate and is relatively inexpensive. A comparison of the detection limits that can be obtained by atomic spectroscopy with various atom reservoirs is contained in Table 8.1. These data show the advantages of individual techniques and also the improvements in detection limits that can be obtained with different atom reservoirs. 

ICP-OES continues to dominate the market because of its ease of use and relatively low maintenance cost. Inductively coupled plasma mass spectrometry (ICP-MS) is a very powerful state-of-the-art technique used for metal analysis of all kinds of samples but requires highly skilled operators. A vast amount of information is received that is not necessarily required as part of problem-solving or routine support. The cost difference and relative freedom from maintenance problems would favour ICP-OES. This book is aimed at practitioners requiring multi-elemental analysis in industrial, environmental, pharmaceutical and research laboratories, where information on identification and quantification is required on a regular basis. The main focus of this book will be on sample preparation, a topic overlooked in most books on atomic spectroscopy. It is aimed at most ICP-OES and ICP-MS users to show that the instrument is useless unless the sample is prepared in a suitable state that can be used to accurately and precisely quantify the metals present. 

X-ray fluorescence spectroscopy (XRF) has been used for many years for the measurement of major and minor elemental concentrations. Improvements made in the sensitivity in recent years now allow the technique to be applied to the analysis of trace elements. A problem is that the sensitivity of XRF decreases dramatically for lower atomic number elements so the technique cannot be used for quantification of elements with atomic numbCT Z < 9. When compared to XRF, modern AA or AE instruments are simpla- to use, less expensive, have similar precision of analysis and have bettCT sensitivity. Optical atomic spectroscopy is ideally suited to the analysis of solutions so the method requires complete dissolution of the powder in a liquid. In comparison, XRE is ideally suited to the analysis of solid samples, and this can be a distinct advantage for cCTamic powders that are commonly difficult to dissolve. Table 3.7 includes a summary of the main features of optical atomic spectroscopy and XRF. 

The previous example illustrates that quantification on entirely polymeric systems is difficult to achieve and often requires elaborate post-modification steps. XPS analysis, however, can provide straightforward information on the presence of hetero-atoms from the graft polymer (e.g., phosphorus, nitrogen, and sulfur) if the substrate polymer does not contain these elements. Moreover, complexation of metal cations such as Fe ", Ni ", and Cu " can also be investigated. XPS is therefore complementary to other analysis techniques, such as UV spectroscopy and ATR-IR spectroscopy. 

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