Resonance Ionization Mass Spectrometry (RIMS) has nowadays reached the stat
us of a routine method for sensitive and selective ultratrace determination
of long-lived radioactive isotopes in environmental, biomedical and techni
cal samples. It provides high isobaric suppression, high to ultra-high isot
opic selectivity and good overall efficiency. Experimental detection limits
are as low as 10(6) atoms per sample and permit the fast and sensitive det
ermination of ultratrace amounts of radiotoxic contaminations. Experimental
arrangements for the detection of different radiotoxic isotopes, e.g. Pu23
6-244, Sr-89,Sr-90 and Tc-99 in environmental samples are described, and th
e application of RIMS to the ultrarare long-lived radioisotope Ca-41 for co
smochemical, radiodating and medical purposes are presented.