The experience of the author and others with the evaporation method is described. The technique consists of evaporating trace amounts of impurities from the molten sample in an electrically heated crucible and condensing them on a water-cooled electrode, which is then arced or sparked. Temperatures used range from 1500 to 2000°C and element sensitivities from 20 to 0.02 ppm.
S. Mandelstam, "Spectrochemical Analysis by the Evaporation Method," Appl. Spectrosc. 11, 157-158 (1957)