Determination of gadolinium in geological samples by inductively coupled plasma mass spectrometry and multivariate calibration

Gadolinium can be difficult to determine by ICP-MS. In a normal geological sample there are risks of spectroscopic interferences on all of its isotopes. In this study this problem has been solved by using partial least squares (PLS) regression. Two PLS models are investigated: the first is based on aqueous standards, and the second on reference materials. Both models are capable of determining Gd with good results in reference materials containing interfering elements. It was not necessary to correct for nonspectroscopic matrix interferences. PLS is compared to principal components regression (PCR), another multivariate calibration method. For the aqueous standards PLS leads to a simpler model, while similar results are obtained for the two methods in the model based on reference materials.