Application to waters and effluents

FLAMELESS ATOMIC ABSORPTION A. Application to waters and effluents 

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. 

Apart from its high sensitivity, the ETA method has a number of additional advantages in the analysis of water and effluents for metals, (a) Only very small samples (1—100 jul) are required for the analysis, (b) Since the sample is dried and ashed in the electrothermal atomiser, pretreatment procedures prior to analysis are often not required. It is possible to introduce waters containing a high level of organic matter directly into the atomiser. 

Since metals are determined at the jug l-1 level in water using the electrothermal atomiser, contamination is a potential problem. Consequently, cleanliness and use of ultra-pure reagents and distilled-deionised water is essential. 

Electrothermal atomisers fall into two classes, i.e. filaments and furnaces. The former category includes all devices in which an electrically heated filament, rod, strip or boat is used and where the atomic vapour passes into an unconfined volume above the viewing area on the other hand, furnaces usually consist of an electrically heated carbon tube into which the sample is injected. The optical axis of the hollow-cathode lamp light beam passes through the centre of this tube. Electrothermal atomisers are connected to a programmable power supply such that the sample can be dried, ashed and atomised at preset temperatures and times. 

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