Thermal stabilization of tellurium in mineral acids solutions: use of permanent modifiers for its determination in sulfur by GFAAS.

The aim of this work is the study of the best conditions for thermal stabilization of tellurium in graphite furnaces under different experimental conditions, including highly concentrated nitric and hydrochloric acids solutions as those resulting of drastic dissolution procedures. The influence of different noble metals used as matrix modifiers in solution or as permanent layers on the graphite furnace will be assessed. Amongst the assayed matrix modifiers, iridium used as permanent has shown the best performance in high concentrations of mineral acids. The mass employed was 20 microg (for 1 ng of Te), with a maximal attainable pyrolysis temperature of 1400 degrees C without losses of the analyte or sensitivity (height, area and form of the atomization peak), being mo=20 pg. Some speculations on the mechanisms of thermal stabilization of tellurium in graphite furnaces will be discussed. The potentiality of ETAAS for tellurium determination in technical grade sulfur will be evaluated. Results involving characteristics mass, limit of detection and percentage of recovery of tellurium in a mineralized sulfur sample will be compared with those obtained through a working curve in absence of interferences.