Wet ashing of whole fish arid standard mammalian liver samples for metal determinations is effectively achieved through low power pulse microwave treatment using a domestic grade microwave oven. The reaction is carried out in an open Erlenmeyer flask while held within a much larger sealed container. The latter may be any inexpensive vessel that is microwave proof. The power setting is approximately 70 watts. The oven is programmed to deliver microwaves for 10 seconds every three minutes for a total of 19 minutes. Efficiency of recovery is generally within 10% of the known amounts. The pulse microwave protocol avoids the high temperatures and pressures that create the risk of explosions.