Micronebulization for trace analysis of lanthanides in small biological specimens by ICP-MS

This work deals with the development of a mass spectrometric method for the determination of lanthanides (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) at ng g−1 levels in small amounts of biological specimens by inductively coupled plasma-mass spectrometry (ICP-MS) after microwave digestion. Two different systems were investigated for introducing the aqueous solutions of the sample into the plasma: a desolvating system (APEX) with micronebulizer and a nano-volume flow injection system combined with a total consumption nebulizer (DS-5). Both solution introduction systems were used together with a quadrupole ICP mass spectrometer. The performances of the investigated nebulizers were compared to that of the MicroMist nebulizer, which was fitted to a mini cyclonic spray chamber. The solution uptake rate was: 700 μL min−1 for MicroMist, 330 μL min−1 for APEX and 8 μL min−1 for DS-5. By using the APEX and the DS-5 nebulizers the oxides formation rate is reduced compared to MicroMist nebulizer, but to a larger extent by APEX. The relative detection limits for lanthanides ranged from 0.57 to 6.1 ng L−1 and 30 to 170 ng L−1 for the APEX and the DS-5 nebulizer, respectively. The absolute detection limits were in the range of 6.7 to 54 pg for APEX and 3.1 to 7.6 fg for DS-5. The method was applied for lanthanides determination in mussel tissue (BCR 668) and in slugs organs. Good precision and accuracy were obtained with the use of APEX, since the oxide interference is markedly reduced. Slight interference was still observed with the use the DS-5 nebulizer, mainly by Ba oxides. By using the nano-volume flow injection nebulizer, lanthanide determination in small amounts of slug tissue was possible, only requiring 76 nL of digested sample solution into the plasma of ICP-MS.