Atomic absorption spectrophotometry instrumentation

Zeeman effect splitting of atomic absorption lines. (Redrawn from Concepts Instrumentation and Techniques in Atomic Absorption Spectrophotometry (R. D. Beaty and J. D. Kerber). Perkin-Elmer,... 

Elemental composition An 89.15%, 0 10.86%. Gold(III) oxide is acid digested, the acid extract diluted appropriately with water and analyzed for gold by atomic absorption spectrophotometry or other instrumental techniques (see Gold). 

Tin can be measured readily at trace concentrations in aqueous solutions by flame or furnace atomic absorption spectrophotometry. For flame AA measurement, air-acetylene flame is suitable. The metal can be identified accurately at 224.6 nm. Tin also can be measured by other instrumental techniques such as ICP-AES, ICP/MS and neutron activation analysis. 

Atomic absorption spectrophotometry was developed in the 1950s by Dr. Alan Walsh.1 The instrumentation of this method is shown in Figure 6.1. In general, chemical compounds are converted into their atomic constituents, and then the light absorption at a wavelength characteristic of a particular atomic species is determined... 

A wide array of laboratory techniques and instrumentation is used in forensic studies. This includes ultraviolet, infrared, and visible spectrophotometry neutron activation analysis gas chromatography and mass spectrophotometry high pressure liquid chromatography and atomic absorption spectrophotometry. The techniques and instrumentation chosen depend on the type of sample or substance to be examined. 

R.D. Beaty, Concepts, Instrumentation and Techniques in Atomic Absorption Spectrophotometry ,... 

Marr and coworkers have described a procedure for the microdetermination of antimony in organoantimony compounds by atomic absorption spectrophotometry. They compared air-acetylene and air-hydrogen flames and prefer the latter on account of the lower noise. The effects of varying instrumental and chemical parameters were also studied. 

One limitation of atomic absorption spectrophotometry is that the samples generally have to be in solution, preferably aqueous. Thus, either the sample must be directly soluble in a suitable solvent or some type of pretreatment, such as acid digestion, is necessary. One exception is that some instruments using a graphite furnace can be modified for direct injection of solids. Another limitation is that only one metal can be analyzed at a time. There are four primary methods of accomplishing this ... 

The technique of flame atomic absorption spectrophotometry accomplishes this by aspirating the sample solution into a burner chamber, where it is mixed with a fuel gas and an oxidant gas. The mixture is then burned in a specially designed burner head (Fig. 2). The light beam is directed lengthway down the burner, and the absorption of the analyte atoms in the flame is measured. The most commonly used gas mixtures are air with acetylene and nitrous oxide with acetylene. Experimental conditions are well-defined in the literature, and cookbook conditions are available from most instrument manufacturers. In addition, many instruments are computer-controlled, and typical conditions are available directly on the operating screen. 

Fig. 3 Typical operation screen for copper using flame atomic absorption spectrophotometry (Courtesy of Perkin-Elmer Instruments.)...

The instrumentation for atomic absorption spectrophotometry is very well-defined and can range from a relatively simple manually operated instrument to a completely automated system that is on line to a central database. In addition, accurate results can be obtained on a wide range of samples. The future lies in using this technique to solve problems rather than to further develop instrumentation. For example, the FDA published new guidelines for the aluminum content of products used in total parenteral nutrition. 

After transport to a laboratory, gases are introduced into an analytical instrument for quantitative determination of the constituents of interest. Soil air in a container is introduced directly to the instmment, whilst adsorbed gas is released by thermal of chemical desorption. The instrumental methods most widely used for gas analyses include gas chromatography, mass spectrometry and atomic absorption spectrophotometry. For quantifying the radiation scars on film, image analysis methods are employed. 

Compare flame emission and atomic absorption spectrophotometry with respect to instrumentation, sensitivity, and interferences. 

Chemical analysis of hazardous substances in air, water, soil, sediment, or solid waste can best be performed by instrumental techniques involving gas chromatography (GC), high-performance liquid chromatography (HPLC), GC/mass spectrometry (MS), Fourier transform infrared spectroscopy (FTIR), and atomic absorption spectrophotometry (AA) (for the metals). GC techniques using a flame ionization detector (FID) or electron-capture detector (BCD) are widely used. Other detectors can be used for specific analyses. However, for unknown substances, identification by GC is extremely difficult. The number of pollutants listed by the U.S. Environmental Protection Agency (EPA) are only in the hundreds — in comparison with the thousands of harmful... 

Analytical Methods for Atomic Absorption Spectrometry, PerkinElmer, Inc. Shelton, CT, 1994. Beaty, R.D. Kerber, J.D. Concepts, Instrumentation and Techniques in Atomic Absorption Spectrophotometry, PerkinElmer, Inc. Shelton, CT, 1993. 

For flame atomic absorption spectrophotometry, the detection limit Is defined as the concentration that produces absorption equivalent to twice the magnitude of the background fluctuation. No mention is made of the blank or blank correction. This definition implies an instrument detection limit rather than a detection limit of a complete analytical procedure. Finally, no mention Is made of the need to determine the variability of responses. 

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