Comparison of INAA and RNAA methods with thermal-ionization mass spectrometry for iridium determinations in atmospheric tracer studies

The sensitivity and precision of instrumental neutron activation analysis ( NAA), radiochemical neutron activation analysis (RNAA), and thermal ionizat ion mass spectrometry (TIMS) are compared for the determination of Ir in am bient size-fractionated aerosol particulate samples. The results of the TIM S analyses indicated high analytical precision (0.2% at >50 pg Ir), but the sensitivity of detection was limited by blank values (300-500 fg). The sen sitivities for INAA and RNAA were comparable, i.e., 60 to 90 fg in size-seg regated particulate samples.