Multi-element Atomic Absorption Spectrometry

Multi-element AAS has been reviewed [112], as well as ETAAS [104] and instrumental aspects of GFAAS [113]. Various monographs on analytical atomic absorption spectrometry are available [52,96,114,115], and on GFAAS [116] and ETAAS [117] more in particular. 

The most frequently applied analytical methods used for characterizing bulk and layered systems (wafers and layers for microelectronics see the example in the schematic on the right-hand side) are summarized in Figure 9.4. Besides mass spectrometric techniques there are a multitude of alternative powerful analytical techniques for characterizing such multi-layered systems. The analytical methods used for determining trace and ultratrace elements in, for example, high purity materials for microelectronic applications include AAS (atomic absorption spectrometry), XRF (X-ray fluorescence analysis), ICP-OES (optical emission spectroscopy with inductively coupled plasma), NAA (neutron activation analysis) and others. For the characterization of layered systems or for the determination of surface contamination, XPS (X-ray photon electron spectroscopy), SEM-EDX (secondary electron microscopy combined with energy disperse X-ray analysis) and... 

Atomic absorption spectrometry has been used to determine thallium in soil [220]. This element has also been determined in multi-metal mixtures by emission spectrometry (Sect. 2.55). 

The second major environmental application of FFF has been the use of an element-specific detector, usually in series with a UV detector, to provide elemental composition data along with the PSD. Graphite-furnace atomic absorption spectrometry has been used off-line on fractions collected from the FFF run. However, the multi-element detection, low detection limits and capability to function as an online detector have made inductively coupled plasma mass spectrometry (ICP-MS) the ideal detector for FFE85-86 The sample introduction system of the ICP-MS is able to efficiently transport micron-sized particles into the high-temperature plasma,... 

Jones JW, Capae SG and O Haver TC (1982) Critical evaluation of a multi-element scheme using plasma emission and hydride evolution atomic-absorption spectrometry for the analysis of plant and animal tissues. Analyst (London) 107 353—377. 

Miller-Ihli NJ (1988) Slurry preparation for simultaneous multi-element graphite furnace atomic absorption spectrometry. J Anal Atom Spectrom 3 73-81. 

Although originally FIA was conceived as a special technique for delivery of a sample segment into the instrument, the combination of flow injection as a sample pretreatment tool with atomic spectrometry has been shown to be of great potential for enhancing the selectivity and sensitivity of the measurements. Moreover, contamination problems are reduced due to the closed system used, making this interface suitable for ultratrace determination of metal species. Hyphenated techniques such as FIA/ SIA with flame atomic absorption spectrometry, inductively coupled plasma (ICP)-optical emission spectrometry, and ICP-mass spectrometry (MS) have been exploited extensively in recent years. The major attraction of FIA-ICP-MS is its exceptional multi-elemental sensitivity combined with high speed of analysis. In addition, the possibility of... 

W. N. L. dos Santos, J. V. S. Santos, L. O. B. Laiana, A. S. Araujo, V. A. Lemos, M. Miro and S. L. C. Ferreira, On-line simultaneous preconcentration procedure for the determination of cadmium and lead in drinking water employing sequential multi-element flame atomic absorption spectrometry, Int. J. Environ. Anal. Chem., 2011, 91(15), 1425-1435. 

Nowadays, atomic absorption spectrometry (AAS) systems are comparatively inexpensive element selective detectors, and some of the instruments also show multi(few)-element capability. There are flame (F AAS), cold vapor (CV AAS), hydride-generating (HG AAS), and graphite furnace (GF-AAS) systems. However, the use of AAS-based detectors for on-line speciation analysis is problematic. F AAS is usually not sensitive enough for speciation analysis at "normal" environmental or physiological concentrations and sample intake is high (4—5 ml/min), which complicates on-line hyphenations with LC an auxiliary flow is necessary. CV AAS and HG AAS use selective derivatization for matrix separation and increased sensitivity for the derivatized species. But, the detector response is species dependent and interferences can be a problem. GF AAS requires only a few microliters of sample and provides low detection limits, between 0.1 and 5 gg/1. Matrix interferences are widely eliminated by Zeeman correction and matrix modifiers nevertheless, quantification errors were reported as atomization temperature does not exceed 2900°C. The most critical problem in respect to speciation analysis is the discontinuous measiuement because of the temperature program operation employed, which takes a few minutes. Therefore, GF AAS is unsuitable for on-line hyphenations as chromatograms carmot be monitored with sufficient resolution. 

Determination of cadmium, lead and nickel by simultaneous multi element flame atomic absorption spectrometry in burned and unburned Venezuelan crude oils, Talanta, 47, 261-66. 

To a hmrted extent, atomic absorption spectrometry can also be used for multielement determinations. Several manufacturers introduced systems with multilamp turrets, where different lamps can be held under pre-heated conditions. Here, rapid switching from one lamp to another enables sequential multi-element determinations to be made by flame atomic absorption, for a maximum of around five elements. Simultaneous determinations are possible with multi-element lamps, however, the number of elements that can be brought together and used as a hollow cathode lamp with a sufficiently stable radiation output and lifetime is rather limited. The use of continuous sources facilitates flexible multi-element determinations for many elements in principle. It is necessary to use high-resolution spectrometers (e.g., echelle spectrometers) with multi-channel detection. CCDs of-... 

Wildhagen, D., Krivan,V., Gercken, B., and Pavel, J. (1996). Multi-element characterization of titanium(IV) oxide by electrothermal atomic absorption spectrometry, inductively coupled plasma atomic emission spectrometry, inductively coupled plasma mass spectrometry and total reflection x-ray fluorescence spectrometry after matrix-analyte separation./AMa/.Ar. Spectrom. 11(5), 371. 

Representative spectra from a lanthanide and an actinide are shown in figs. 21 and 22. The most abundant analyte peaks are from monatomic ions (M" ), and these are observed at sensitivities of 10 -10 count s per mg in solution. Ion count rates as low as 2counts s can be distinguished from the background, so the detection limits for most elements are of the order of 10-100 ng/ . At present, these powers of detection are superior to those obtainable with any other common multi-element technique. Atomic absorption spectrometry with electrothermal vaporization does provide detection limits in a similar range but is generally used only for single-element determinations. 

The linear dynamic range of an ICP-MS instrument is typically about 4-6 orders of magnitude, while the sensitivity is often 3 orders of magnitude better than the ICP-AES technique. While the detection limits for many elements with ICP-MS are better or comparable to AES and graphite furnace atomic absorption spectrometry, the simultaneous multi-elemental detection afforded by ICP-MS clearly places this technique in the lead for analytical utility and versatility. 

The potential for the employment of plasma emission spectrometry is enormous and it is finding use in almost every field where trace element analysis is carried out. Some seventy elements, including most metals and some non-metals, such as phosphorus and carbon, may be determined individually or in parallel. As many as thirty or more elements may be determined on the same sample. Table 8.4 is illustrative of elements which may be analysed and compares detection limits for plasma emission with those for ICP-MS and atomic absorption. Rocks, soils, waters and biological tissue are typical of samples to which the method may be applied. In geochemistry, and in quality control of potable waters and pollution studies in general, the multi-element capability and wide (105) dynamic range of the method are of great value. Plasma emission spectrometry is well established as a routine method of analysis in these areas. 

For rapid analysis during the production process atomic absorption is mainly of indirect value because, due to the sequential character of the technique, it cannot be used for complete steel or slag analysis in a two to three minute period. The analytical requirements for the testing of rapid continuous production processes are fulfilled by the techniques of emission and X-ray spectrometry. These techniques are characterised by great speed, high precision and simultaneous multi-element analysis. Accuracy must, however, be constantly checked with a variety of special calibration samples. This requires the determination of the true concentrations of the calibration samples with chemical methods of solution analysis, whose precision is often only equal to or, when compared with X-ray spectrometry, frequently poorer. Chemical analysis is, however, the basis of all comparisons, and must be repeated frequently for the determination of the true concentrations. Atomic absorption, with its relatively good precision, has greatly simplified the analytical control of numerous elements. 

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