The graphite furnace temperature program used for the trapping, pyrolysis and atomization of mercury is shown in Table 1. The graphite tubes were previously treated with gold as permanent modifier by pipetting 40.0 μL of a 1.0 g L− 1 gold standard solution into the tube, and submitting it to the temperature program based on a previous work [16], using pyrolysis at 160 °C, atomization at 900 °C and cleaning at 1000 °C. This procedure was repeated fifteen times, resulting in a total mass of 600 μg of gold deposited on the tube wall.