For routine REE analysis of rocks and minerals, the detection limit is at or below chondrite levels. Zr is measured only as a check for complete dissolution of the sample. Samples are first ground in an iron bowl in a shatterbox swing mill. The instrumentation consists of a Sciex Elan model 250 ICP-MS equipped with a Babington nebulizer, water cooled spray chamber, and Brooks mass flow controllers. Plasma power is 1500 watts.
Most elements have more than one isotope.
For these elements the selection of the isotope for measurement is based on relative abundance and freedom from oxide and isobaric interferences. Table 1 lists the isotopes measured and their potential interfering oxides. Their elemental concentrations so derived are listed in table 2. Concentrations for the unknown samples are then computed from this curve. E is the mass weighted drift correction for the mass i of the element E, calculated using the internal standards 115In and 187Re.