Determination of long-lived radionuclides by inductively coupled plasma quadrupole mass spectrometry using different nebulizers

Different nebulizers (cross-flow, ultrasonic and two microconcentric nebuli zers) were used for sample introduction of radioactive solutions into a qua drupole-based inductively coupled plasma mass spectrometer (ICP-QMS). The b est sensitivity (from 420 to 850 MHz, which is about one order of magnitude higher in comparison with the crossflow nebulizer) for long-lived radionuc lides (Ra-226, Th-230, Np-237, U-238 and Am-241) was observed using the ult rasonic nebulizer. However, using the ultrasonic nebulizer, a significantly higher sample size (26-fold) in comparison with the micronebulizers is req uired. Sample introduction by micronebulization with a small sample size in the low picogram range is the method of choice for the determination of lo ng-lived radionuclides. The precision of determination of a 10 ng l(-1) con centration was in the low-% range (and sub-% range) for all measurements us ing different nebulizer types. The detection limits for the determination o f long-lived radionuclides in aqueous solutions applying the different nebu lizers were 0.01-0.6 ng l(-1). The flow injection analysis approach was opt imized for isotope dilution analysis of Th-232 (using 20 mu l of 5 mu g l(- 1) Th-230) by ICP-QMS. The isotopic abundance ratios of Th-230-Th-232 isoto pe mixtures (Th-230/Th-232 = 0.01, 0.001 and 0.0001) were determined using a microconcentric nebulizer and 1 mu g l(-1) Th solutions with a relative e xternal standard deviation of long-term stability measurements (over 20 h) of 0.17, 0.62 and 2.66%, respectively.