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3.8 Applications
Electrothermal atomization is particularly useful when the amount of sample is very small, when very
low levels of detection are required and when the matrix is dilute or volatile. These criteria often apply
to clinical samples (a pin-prick sample of blood produces only 50-100 mm of whole blood, but this is
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sufficient for analysis using an electrothermal atomizer, hence it is not essential for an intravenous
sample to be taken). For such samples, often pretreatment is not required, and body fluids and
biological tissues can be ashed in situ in the furnace. This also applies to some foods, although others
may need some preliminary wet ashing.
Oils can be injected directly or in a dilute form, e.g. diluted with xylene. Organometallic standards are
recommended.
Metallurgical samples are perhaps not as amenable to electrothermal atomization as some types of
sample, but as high sensitivity is often only required for the most volatile elements, useful information
can be obtained. Problems may be encountered from chloride when using aqua regia to dissolve
samples. An interesting application is the placing of weighed solid samples directly into the furnace for
ultra-trace analysis of volatile elements. This procedure is, however, notoriously imprecise, as the
accurate weighing of samples of less than 10 mg is difficult.
Waters are the subject of a voluminous literature, and various methods have been proposed to
overcome some of the interferences encountered, e.g. by adding ascorbic acid or lanthanum to remove
interferences when determining lead in hard water. Saline waters present particular problems (e.g. from
background absorption), and a preliminary separation may be advisable.
Air particulates are usually dissolved before analysis, but again, solid samples (e.g. on glass-fibre
filters) have been analysed directly in furnaces.
The standard addition method of calibration (see Chapter 1) is often used to combat the uncertainties
of varying interference effects in electrothermal atomization. However, care should be taken with this
approach, as errors from spurious blanks and background may go undetected. It must also be
emphasized that the technique of standard additions does not correct for all types of interference.
The literature on applications of electrothermal atomizers is now extremely large and, because of the
details of the furnace programmes used, is well worth consulting. The tables in the Atomic
Spectrometry Updates reports (see Appendix C) offer the best way of accessing this information.
Q. Why is electrothermal atomization widely used in clinical applications?
Q. What are the advantages and disadvantages of the standard addition method for the above
applications?
