Studies on the long-term stabilities of the background of radionuclides in inductively coupled plasma mass spectrometry (ICP-MS)

The long-term stabilities of the ICP-MS background of nine radionuclides are studied, of which the signals are partially superimposed by polyatomic interferences or affected from carry-over and memory effects. The background generated by the ICP flame, by two pure waters, and by nitric acid (2% v/v) was investigated in detail. A minimum of 50 measurement points was used for each long-term investigation. The detection limits of the radionuclides of the masses 90 amu (⁹⁰Sr: 30 Bq/mL), 99 amu (⁹⁹Tc: 4 mBq/mL), 238 amu (²³⁸U: 10 nBq/mL), and 244 amu (²⁴⁴Pu: 0.6 Bq/mL) are calculated from the mean standard deviation of the background signals. For all nine radioisotopes, the calculated detection limits are between 0.8 and 6 pg/mL. While the detection limit of the mass 90 amu is blank limited, those of the mass 99 amu and the actinides are totally uneffected by the blank solutions. The detection limits are compared with those given in literature.