AAS—See Atomic absorption spectroscopy

Atomic absorption spectroscopy (AAS) is complementary to atomic emission spectroscopy (see Section 3.5.3) and became available for a wide range of atoms in the mid-1950s. 

Atomic absorption spectroscopy (AAS) is the most prevalent analytical technique for measuring low levels of barium and its compounds (i.e., barium carbonate, barium sulfate, and barium chloride) in air, water, waste water, geological materials (calcium carbonate), unused lubricating oil, and diagnostic meals containing barium sulfate (see Table 6-2). 

For many years there was no sufficiently specific method for the identification of characteristic GSRs. One could not see metallic particles because of their small size (5-50 pm) and their presence was ascertained indirectly by means of colouring chemical reactions or such instrumental methods as atomic absorption spectroscopy (AAS), neutron activation analysis (NAA) or XRF. These methods, however, are... 

Atomic absorption spectroscopy (AAS) determination of solubilized soil metal content found the highest metal sorption for the roots of cultivars Montserrat and Feline (see Figure 2). 

Atomic absorption spectroscopy (AAS) - See Techniques for Materials Characterization, page 12-1. 

Why did dc polarography rapidly disappear from analytical laboratories in the mid-1950 s The main application of dc polarography in analysis was to heavy metal cation analysis and the detection limit here is about 10 mol dm - (ca 6 ppm for copper). In the mid 1950 s atomic absorption spectroscopy (AAS) became available and was routinely used to analyse for heavy metal cations at <1 ppm. Atomic absorption spectroscopy, although more expensive in initial costs, is an easier technique to use than polarography. Atomic absorption spectroscopy became rapidly established as the method of choice and has remained so until the present day. It is only in recent years that advanced forms of polarography using pulse techniques have begun to become competitive with AAS (see Section 3.0 and 4.0). 

Atomic emission spectroscopy (AES) and atomic absorption spectroscopy (AAS) are In a manner similar to our discussion of molecular spectroscopy, where we compared UV absorption with UV excitation and subsequent fluorescence, these two determinative approaches are the principal ways to identify and quantitate trace concentration levels of metal contamination in the environment. As the need developed to quantitate increasing numbers of chemical elements in the Periodic Table, so too came advances in instrumentation that enabled this to be achieved at lower and lower IDLs AES and AAS techniques are both complementary and competitive. Atomic fluorescence spectroscopy (AFS) is a third approach to trace metal analysis. However, instrumentation for this has not as yet become widespread in environmental testing labs and it is unlikely that one would see atomic or what has become useful x-ray atomic fluorescence spectroscopy. Outside of a brief mention of the configuration for AFS, we will not cover it here. 

Numerous procedures, by a variety of different instruments, are available to quantify the amount of thallium present in hair, blood, tissue, saliva, and urine (for reviews, see [9,81]). Instrumentation used includes emission spectrography, flame and flameless atomic absorption spectroscopy (AAS), voltammetry, neutron activation analysis, and field desorption mass spectroscopy [13,17,82-90]. Field desorption mass spectroscopy when combined with stable isotope dilution can detect fentomole quantities and has value in that no tissue preparation (other than homogenization) is required [65,82,89], The use of these two methods, however, is restricted to specialized laboratories. 

In 1C, the election-detection mode is the one based on conductivity measurements of solutions in which the ionic load of the eluent is low, either due to the use of eluents of low specific conductivity, or due to the chemical suppression of the eluent conductivity achieved by proper devices (see further). Nevertheless, there are applications in which this kind of detection is not applicable, e.g., for species with low specific conductivity or for species (metals) that can precipitate during the classical detection with suppression. Among the techniques that can be used as an alternative to conductometric detection, spectrophotometry, amperometry, and spectroscopy (atomic absorption, AA, atomic emission, AE) or spectrometry (inductively coupled plasma-mass spectrometry, ICP-MS, and MS) are those most widely used. Hence, the wide number of techniques available, together with the improvement of stationary phase technology, makes it possible to widen the spectrum of substances analyzable by 1C and to achieve extremely low detection limits. 

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... 

---