Model calculation of the characteristic mass for convective and diffusive vapor transport in graphite furnace atomic absorption spectrometry

A combination of former convective-diffusive vapor-transport models is described to extend the calculation scheme for sensitivity (characteristic mass - m(0)) in graphite furnace atomic absorption spectrometry (GFAAS). This approach encompasses the influence of forced convection of the internal furnace gas (mini-flow) combined with concentration diffusion of the analyte atoms on the residence time in a spatially isothermal furnace, i.e., the standard design of the transversely heated graphite atomizer (THGA). A couple of relationships for the diffusional and convectional residence times were studied and compared, including in factors accounting for the effects of the sample/platform dimension and the dosing hole. These model approaches were subsequently applied for the particular cases of Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Mo, Ni, Pb, Sb, Se, Sn, V and Zn analytes. For the verification of the accuracy of the calculations, the experimental mo values were determined with the application of a standard THGA furnace, operating either under stopped, or mini-flow (50 cm(3) min(-1)) of the internal sheath gas during atomization. The theoretical and experimental ratios of mo(mini-flow)-tomo(stop-flow) were closely similar for each study analyte. Likewise, the calculated mo data gave a fairly good agreement with the corresponding experimental mo values for stopped and mini-flow conditions, i.e., it ranged between 0.62 and 1.8 with an average of 1.05 +/- 0.27. This indicates the usability of the current model calculations for checking the operation of a given GFAAS instrument and the applied methodology. (C) 2015 Elsevier B.V. All rights reserved.