Electrotherm al Atomic Absorption Spectrom etry of

Electrothermal atomic absorption spectrometry has five major advantages for measurements of trace metals in biological materials, in comparison to measure­ ments by conventional flame atomic absorption analysis: (1) Trace metal contami­ nation is minimized by avoidance of preliminary chemical extractions and addi­ tions of reagents; (2) Sample volumes are small (1 to 50 /*1). The entire sample is vaporized in electrothermal atomization, whereas in most flame nebulization systems only a small fraction of the sample enters the flame; (3) Atoms are re­ leased in higher concentrations. In electrothermal atomization, the atom cloud is released into a relatively small volume of gas. In contrast, in flame atomization, the atom cloud is diluted by the high flow rate of gases and by expansion of gases during combustion; (4) Molecular recombination of atoms is retarded by the at­ mosphere of inert gas which restricts chemical reactions (e.g., oxidation). In contrast, in flame atomization, oxidation occurs very rapidly; and (5) By pro­ grammed increments in. temperature, electrothermal atomization permits or­ ganic constituents to be pyrolyzed prior to vaporization and atomization of metals. Despite these advantages, electrothermal atomic absorption is particularly subject to interferences and sources of imprecision which necessitate critical evaluations in the prospective analyst’s laboratory before an electrothermal method can be confidently employed for diagnostic measurements of a specific trace metal in body fluids.