Electrothermal atomisation, ETA

In addition to the normal requirements of a good atomic absorption spectrometer two parameters are of paramount importance when employing a furnace as the atomising source. These are (a) the response time of the signal handling circuitry must be sufficiently rapid to capture the transient absorption signals which are characteristic of furnace atomisers, and (b) the 

Certainly all of the development work using these devices and indeed much of today s routine analyses were performed using a chart recorder to display the analytical peaks. The value of such a dynamic visual display cannot be overemphasised, for the following reasons. 

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Flameless atomic absorption using an electrothermal atomiser is essentially a non-routine technique requiring specialist expertise. It is slower than flame analysis only 10—20 samples can be analysed in an hour furthermore, the precision is poorer (1—10%) than that for conventional flame atomic absorption (1%). The main advantage of the method, however, is its superior sensitivity for any metal the sensitivity is 100—1000 times greater when measured by the flameless as opposed to the flame technique. For this reason flameless atomic absorption is employed in the analysis of water samples where the flame techniques have insufficient sensitivity. An example of this is with the elements barium, beryllium, chromium, cobalt, copper, manganese, nickel and vanadium, all of which are required for public health reasons to be measured in raw and potable waters (section I.B). Because these elements are generally at the lOOjugl-1 level and less in water, their concentration is below the detection limit when determined by flame atomic absorption as a result, an electrothermal atomisation (ETA) technique is often employed for their determination. 

The disadvantages of electrothermal atomisation (ETA) — atomic absorption spectrometry (AAS) are the physical, chemical and spectral interferences, these being more severe than with flame atomic absorption spectrometry (FAAS), and which depend critically upon the experimental and operational conditions within the atomiser and the nature of the chemical pretreatment used. It is not intended to discuss here the theoretical aspects of these interferences which have been reviewed excellently elsewhere [2], but it is pertinent to consider briefly how these interferences affect the various stages of the analysis and how they may be minimised. 

Atomic absorption spectrophotometry (AAS) is one of the most widely used methods. Either flame atomisation or electrothermal atomisation (ETA) using the graphite furnace is employed. Some useful references are given in the Bibliography. 

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