Boxes 5 Analysis of a sample dilution factor

The method of calcLilation is most appropriately done as follows  

The expansion chamber (Fig. 27.7) has two functions. The first is concerned with aerosol generation the objectives of which are  

The second function involves the safe pre-mixing of the oxidant and fuel gases before they are introduced into the laminar flow burner. 

As AAS is used to monitor one metal at a time, the spectrometer used is termed a monochromator. Two optical arrangements are possible single and double beam. The latter is preferred as it corrects for fluctuations in the HCL caused by warm-up, drift and source noise, thus leading to improved precision in the absorbance measurement. A schematic diagram of the optical arrangement is shown in Fig. 27.8. The attenuation of the HCL radiation by the atomic vapour is detected by a photomultiplier tube (PMT), a device for proportionally converting photons of light to electric current. 

One of the main practical problems with the use of AAS is the occurrence of molecular species that coincide with the atomic signal. One approach to remove this molecular absorbance is by the use of background correction methods. Several approaches are possible, but the most common is based on the use of a continuum source, D2. In the atomization cell (e.g. flame) absorption is possible from both atomic species and from molecular species (unwanted interference). By measuring the absorption that occurs from the radiation source (HCL) and comparing it with the absorbance that occurs from the continuum source (D2) a corrected absorption signal can be obtained. This is because the atomic species of interest absorb the specific radiation associated with the HCL source, whereas the absorption of radiation by the continuum source for the same atomic species will be negligible. 

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