Sample preparation for electrothermal atomisation—AAS

According to Stoeppler et al. [15], severe errors up to a factor of two may result from ETA—AAS analysis of biological materials without some form of sample pretreatment. The approaches that will be discussed here are (a) the use of diluent solutions to minimise matrix and molecular absorption interferences (b) partial decomposition techniques in which metals are extracted from proteins with acids (c) dissolution of tissue samples without complete oxidation (d) complete oxidation procedures such as dry ashing, wet digestion at ambient and elevated pressures, and low temperature ashing with reactive gases at low pressures. 

A few simple chemical reagents may be added to biological samples in order to minimise molecular absorption interferences by providing a more complete oxidation within the atomisation cell, or to minimise the effect of the matrix upon analyte sensitivity either by modifying the volatility of the analyte, or the matrix, or both. 

Other volatile elements, e.g. As, Se, may be converted to the less volatile arsenides and selenides by the addition of Ag or Ni salts. Ashing temperatures of up to 1200°C for Se and 1400°C for As may then be used without volatilisation losses [19, 21, 22]. 

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