Enhancement of sensitivity in atomic-absorption spectrometry by addition of a graphite lid to a cup furnace.

By using a cup furnace covered with a graphite lid, it is possible to enhance the atomic-absorption signal for Cd, Zn, Sb, Pb, In, Cu and Fe in solution and for Pb in tin metal (directly atomized). When the analyte is atomized in the cup furnace, part of it condenses on the lid, from which it can be re-evaporated and atomized to give a second absorption signal and hence greater sensitivity. When the lid is small, so that the temperature lag is short, the initial atomic-absorption intensity is also enhanced. The enhancement is due to an increased residence time of the atomized analyte in the cup.