Page 185 - An Introduction to Analytical Atomic Spectrometry - L. Ebdon

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B.4.6 References

1. Skoog, D.A. and Leary, J.A. (1992) Principles of Instrumental Analysis, 4th edn, Saunders College
Publishing, Orlando, Florida, USA.

2. Christian, G.D. (1994) Analytical Chemistry, 5th edn, Wiley, New York.

3. Alkemade, C.T.J. and Herrmann, R. (1979) Fundamentals of Analytical Flame Spectroscopy, Hilger,
Bristol.

4. Cresser, M. (1994) Flame Spectrometry in Environmental Chemical Analysis: a Practical Guide,
Royal Society of Chemistry, Cambridge.

5. Miller, J. C. and Miller, J.N. (1993) Statistics for Analytical Chemistry, 3rd edn, Ellis Horwood,
Chichester.

B.5 Graphite Furnace Atomic Absorption Spectrometry
B.5.1 Objectives.

Optimization of drying, ash and atomization temperatures; calibration and determination of Cu.
B.5.2 Introduction

The technique is prone to very severe interference effects unless certain precautions are taken. The
sample is dried, ashed and atomized according to the temperatures programmed into the instrument.
Each stage has its own potential problems, and therefore each stage must be optimized. If the drying
stage is too hot, the sample may boil vigorously and splatter across the tube, causing problems with
precision. If too low a temperature is used, the time required for drying increases to such an extent that
the entire programme is prohibitively long. The temperature used should be approximately 20°C higher
than the boiling point of the solvent, but in any case should lead to steady, even drying of the sample.
This can be observed by the use of a mirror.

If the ash stage temperature is incorrectly set, several problems may arise. If it is too low, the matrix
(i.e. the components in the sample that can lead to interferences) is not removed and hence they obscure
the light beam when atomic absorption is being measured. If it is too high, then the analyte may be lost
by volatilization as a salt (often chlorides) or by atomization. It is therefore necessary to construct an
'ash curve' to determine the optimum ash temperature.

The atomize temperature should also be optimized. If too low a temperature is used, the analyte will not
atomize and hence no signal will