Indium atomic absorption signals from non-pyrolytic and pyrolytically coated graphite furnaces in electrothermal atomization atomic absorption spectrometry

In the ETAAS determination of In, double and single peak signals were observed when non-pyrolytic and pyrolytic graphite (PG) furnaces, respectively, were used. Since Arrhenius plots for the single peak signal in the PG furnace were composed of two straight line segments, it was proposed that the single peak signal possibly comprises two unresolved pulses. The effects of Zr- and W-treated furnaces, and O2 and CO additives, on the charring temperature, atomic absorption response, pulse shape, appearance temperature of atomic absorption response and kinetic data were investigated. The following processes were proposed as atomization mechanisms in both furnaces: for the first pulse, direct heterogeneous reduction of In2O(g) on the hot graphite wall to form In(g); for the second pulse, direct reduction of In2O3 on the hot graphite wall to form the metal followed by atomization via gaseous In dimers. It was also found that the sensitivity loss reaction, proposed as the thermal dissociation of In2O3(s) to form In2O(g), is catalyzed by carbon atoms from the furnace wall.