Lanthanide and actinide impurities in a total sample of 1 to 10 μg of transuranic matrix can be determined by employing the spark-source mass spectrograph and solution technique. A special source glove box permits safe manipulation of transuranium elements with α-emitting radioactivity up to 1012dpm. The minimum detection limit is about 1012atoms per electrode system and an exposure of 10−8coulomb. Relative sensitivity values for the lanthanides and actinides were established with respect to erbium, the internal standard.