Direct insertion of trace metals preconcentrated on activated charcoal into an inductively coupled plasma

Trace metals have been concentrated onto activated charcoal by using oxalic acid, iminodiacetic acid, and 8-hydroxyquinoline. The charcoal was directly analyzed in an ICP by placing several particles in a direct sample insertion (DSI) cup, or fabricating a DSI probe with an activated charcoal cap. Detection limits in the tens to hundreds of parts per trillion were found for Pb, Cd, Zn, and Cu. The recovery for Cu was 2-5% but may be improved by reactivation of the plasma-cleaned charcoal. Cleaning the charcoal, derived from wood, in the plasma prior to adsorption was necessary to remove trace metals.