Influence of pressure and atomizer length on absorption curves in ETA-AAS measurements for standardless analysis

A new method for standardless analysis in electrothermal atomic absorption spectroscopy has been recently proposed whose implementation requires the use of special atomizers and power supplies not available in the market. Up to now, with the proposed method, only volatile elements have been determined with good results because it can be applied only if all atoms injected are simultaneously present in the atomizer for a time interval sufficiently long that a good value of absorbance can be measured. This can be obtained if the heating rate is sufficiently high and the removal of atoms from the atomizer slow. From a theoretical model based only on diffusion, it can be deduced that the possibility of standardless analysis in the mode described above can be enhanced if the length of the atomizer is increased and the diffusion coefficient of the analyte is decreased. From the results obtained by comparing data from atomizers of 36 and 50 mm in length and at different pressures, it can be inferred that the removal mechanism is basically controlled by diffusion but that other mechanisms, like convection, are also present. Received: 2 May 1997 / Revised: 15 December 1997 / Accepted: 15 January 1998