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 absorp tion spectroscopy has been recently proposed whose implementation requ ires the use of special atomizers and power supplies not available in the market. Up to now, with the proposed method, only volatile element s have been determined with good results because it can be applied onl y 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 theoreti cal model based only on diffusion, it can be deduced that the possibil ity of standardless analysis in the mode described above can be enhanc ed if the length of the atomizer is increased and the diffusion coeffi cient of the analyte is decreased. From the results obtained by compar ing data from atomizers of 36 and 50 mm in length and at different pre ssures, it can be inferred that the removal mechanism is basically con trolled by diffusion but that other mechanisms, like convection, are a lso present.