Direct current inductively coupled spectrometry

Despite the absence of any known biological roles for strontium, analysis of trace amounts of the alkali earth metal in many environmental and industrial samples and, especially, in radioactive waste is of critical importance. Techniques applicable for analyzing strontium in environmental or biological material are atomic absorption spectrometry (AAS), inductively coupled plasma atomic emission spectrometry (ICP-AES), direct-current plasma echelle spectrometry, neutron activation analysis and X-ray fluorescence. For most applications, the first two mentioned methods are of interest because, in general, they allow... 

Inductively coupled plasma (icp) emission, direct current plasma (dcp), and inductively coupled plasma mass spectrometry (icp/ms) have taken over as the methods of choice for the simultaneous detection of metallic impurities in hafnium and hafnium compounds (29,30). 

Inductively coupled argon plasma (icp) and direct current argon plasma (dcp) atomic emission spectrometry are solution techniques that have been appHed to copper-beryUium, nickel—beryUium, and aluminum—beryUium aUoys, beryUium compounds, and process solutions. The internal reference method, essential in spark source emission spectrometry, is also useful in minimizing drift in plasma emission spectrometry (17). Electrothermal (graphite... 

There are two popular types of plasma sources l) the direct current plasma (DCP), and 2) the inductively coupled plasma (ICP). In the commercial version of the former plasma source (marketed by Spectrometries, Inc.), the sample is aspirated with argon through a small orifice into a chamber where the large droplets settle out and the fine mist is conveyed by the argon stream through a chimney to the vertex of a plasma which is in the form of... 

The most suitable techniques for the rapid, accurate determination of the elemental content of foods are based on analytical atomic spectrometry, for example, atomic absorption spectrometry (AAS), atomic emission spectrometry (AES), and mass spectrometry, the most popular modes of which are Game (F), electrothermal atomization (ET), and hydride generation (HG) AAS, inductively coupled plasma (ICP), microwave-induced plasma (MIP), direct current plasma (DCP) AES, and ICP-MS. Challenges in the determination of elements in food include a wide range of concentrations, ranging from ng/g to percent levels, in an almost endless combination of analytes with matrix speci be matrices. 

Figure 3.2 Direct-current arc (after G.L. Moore, Introduction to Inductively Coupled Plasma. Atomic Emission Spectrometry, p. 35. C 1989, with the permission of Elsevier Science, Amsterdam).

As shown in Table 28-1, several methods are used to atomize samples for atomic spectroscopic studies. Inductively coupled plasmas, flames, and electrothermal atomizers are the most widely used atomization methods we consider these three methods as well as direct current plasmas in this chapter. Flames and electrothermal atomizers are widely used in atomic absorption spectrometry, while the inductively coupled plasma is employed in optical emission and in atomic mass spectrometry. 

Inductively coupled plasma (ICP) and direct current plasma (DCP) atomic emission spectrometry have become widely accepted techniques for simultaneous multielemental analysis. These techniques are highly sensitive and have a very wide dynamic range. A wealth of information is contained in the emission signal, including several atomic and ionic emission lines for each element in the sample. In even the simplest sample, there are thousands of observable spectral lines. To make full use of this enormous spectral information the analyst requires an instrument capable of observing a very wide spectral range simultaneously, preferably from 190 nM to 800 nM with a resolution of approximately 0.01 nM. 

Techniques under this heading obviously include the most common and popular one of inductively coupled plasma atomic emission spectrometry (IGPAES), also at times simply denoted plasma emission spectrometry, but can also be extended to include direct current plasma atomic emission spectrometry (DGPAES) and graphite furnace IGPAES as well as variants. 

Mass Spectrometric Detection. The very small volumetric flow rates of less than 1 pi,/min from electrophoresis capillaries make it feasible to couple the effluent directly to the Ionization source of a mass spectrometer. The most common sample-introduction and ionization interface for this purpose is currently electrospray (Section 20B-4), although fast atom bombardment, matrix-assisted laser desorption-ionization (MALDI) spectrometry, and inductively coupled plasma mass spectrometry (ICPMS) have also been used. Because the liquid sample must be vaporized before entering the mass spectrometry (MS) system. 

Inductively coupled plasma-atomic emission spectroscopy (ICP-AES) is used for multi-element determinations in blood and tissue samples. Detection in urine samples requires extraction of the metals with a polydithiocarbamate resin prior to digestion and analysis (NIOSH 1984a). Other satisfactory analytical methods include direct current plasma emission spectroscopy and determination by AAS, and inductively coupled argon plasma spectroscopy-mass spectrometry (ICP-MS) (Patterson et al. 1992 Shaw et al. 1982). Flow injection analysis (FIA) has been used to determine very low levels of zinc in muscle tissue. This method provides very high sensitivity, low detection limits (3 ng/mL), good precision, and high selectivity at trace levels (Fernandez et al. 1992b). 

The roots of ICP-MS began in the mid-1960s with the advent of a technique called inductively couple plasma—atomic emission spectrometry (ICP-AES). For decades, prior to this, atomic emission spectrometry (flame, direct current-arc, and controUed-waveform spark) was the predominant method used for elemental analysis. The work of Greenfield et al. (1964) and work done essentially simultaneously by Wendt and Fassel (1965) introduced an emission spectrometric technique that provided high sensitivity trace element analysis with a multielement detection capability. This technique is still widely used today and can be studied in publications by Boumans (1987) and Montaser and Golightly (1992). 

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