Spectrometric techniques optical emission spectrometry

In terms of this group of atomic spectrometric techniques, optical emission spectrometry (OES) is the oldest and most established. Atomic absorption spectrometry (A AS) and atomic fluorescence spectrometry (AES) are two other important types of atomic spectrometry techniques. In this section, AAS and AES will be discnssed only briefly elemental analysis based on ICP spectrometry will be discnssed in more detail, specifically ICP-OES... 

The basic instrumentation used for spectrometric measurements has already been described in the previous chapter (p. 277). Methods of excitation, monochromators and detectors used in atomic emission and absorption techniques are included in Table 8.1. Sources of radiation physically separated from the sample are required for atomic absorption, atomic fluorescence and X-ray fluorescence spectrometry (cf. molecular absorption spectrometry), whereas in flame photometry, arc/spark and plasma emission techniques, the sample is excited directly by thermal means. Diffraction gratings or prism monochromators are used for dispersion in all the techniques including X-ray fluorescence where a single crystal of appropriate lattice dimensions acts as a grating. Atomic fluorescence spectra are sufficiently simple to allow the use of an interference filter in many instances. Photomultiplier detectors are used in every technique except X-ray fluorescence where proportional counting or scintillation devices are employed. Photographic recording of a complete spectrum facilitates qualitative analysis by optical emission spectrometry, but is now rarely used. 

Today, as a direct solid-state analytical technique, dc GDMS is more frequently applied for multi-element determination of trace contaminants, mostly of high purity metallic bulk samples (or of alloys) especially for process control in industrial laboratories. The capability of GDMS in comparison to GD-OES (glow discharge optical emission spectrometry) is demonstrated in a round robin test for trace and ultratrace analysis on pure copper materials.17 All mass spectrometric laboratories in this round robin test used the GDMS VG 9000 as the instrument, but for several... 

Different analytical techniques such as ICP-OES (optical emission spectrometry with inductively coupled plasma source), XRF (X-ray fluorescence analysis), AAS (atomic absorption spectrometry) with graphite furnace and flame GF-AAS and FAAS, NAA (neutron activation analysis) and others, are employed for the trace analysis of environmental samples. The main features of selected atomic spectrometric techniques (ICP-MS, ICP-OES and AAS) are summarized in Table 9.20.1 The detection ranges and LODs of selected analytical techniques for trace analysis on environmental samples are summarized in Figure 9.15.1... 

Spectrometric techniques based on atomic absorption or the emission of radiation flame atomic absorption spectrometry (FAAS), electrothermal atomic absorption spectrometry (ETAAS), inductively coupled plasma-optical emission spectrometry (ICP-OES), inductively coupled plasma-mass spectrometry (ICP-MS), and cold vapor (CV)/hydride generation (HG), mainly for trace and ultratrace metal determinations. 

When compared with optical spectrometric techniques of elemental analysis, the techniques based on mass spectrometry provide an increase in sensitivity and in analytical working range of some orders of magnitude. For instance, the detection limits with ICP-MS are three orders of magnitude better than ICP-optical emission spectrometry (ICP-OES). Figure 1.45 shows the maximum sensitivity obtained for the different elements, using an ICP-MS coupling with a quadrupole. 

For determination of the elements, mainly spectrometric techniques are used here. Depending on the kind of element and the expected concentration level, the following methods are applied flame atomic emission spectrometry (flame AES), flame atomic absorption spectrometry (flame AAS), inductively coupled plasma optical emission spectrometry (ICP-OES), electrothermal atomisation (graphite furnace) atomic absorption spectrometry (ETA-AAS), inductively coupled plasma mass spectrometry (ICP-MS), spectrophotometry and segmented flow analysis (SFA). Besides, potentiometry (ion selective electrodes (ISE)) and coulometry will be encountered. In many cases, more than one method is described to determine a component. This provides a reference, as well as an alternative in case of instrumental or analytical problems. 

Atomic Spectrometric Techniques Optical Detection Atomic Emission Spectrometry Atomic Absorption Spectrometry Atomic Fluorescence Spectrometry Detection of Elemental Ions Comparisons of the Atomic Spectrometric Techniques... 

Plasma sources were developed for emission spectrometric analysis in the late-1960s. Commercial inductively coupled and d.c. plasma spectrometers were introduced in the mid-1970s. By comparison with AAS, atomic plasma emission spectroscopy (APES) can achieve simultaneous multi-element measurement, while maintaining a wide dynamic measurement range and high sensitivities and selectivities over background elements. As a result of the wide variety of radiation sources, optical atomic emission spectrometry is very suitable for multi-element trace determinations. With several techniques, absolute detection limits are below the ng level. 

In this chapter, we first present a theoretical discussion of the sources and properties of optical atomic spectra. We then list methods used for producing atoms from samples for elemental analysis. Finally, we describe in some detail the various techniques used for introducing samples into the devices that arc used for optical absorjHion, emis-, sion, and fluorescence spectrometry as well as atomic mass spectrometry. Chapter 9 is devoted to atormc.absorption methods, the most widely used of all the. atomic spectrometric techniques. Chapter 10 deals with several types of atomic emission techniques. Brief chapters on atomic mass spectrometry and atomic X-ray methods follow this discussion. 

Atomic absorption, plasma atomic emission, and atomic fluorescence spectrometry are all optical atomic spectrometric techniques developed rapidly during the past years. These methods are based on the measurement of absorption, emission, or fluorescence originated from the free, unionized atoms or atomic ions in gas phase. 

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