Below is the original Table 4, in which Mass 8, for which no isotope exists, was used to hold a correction factor. The red part of the equation at Mass 8 is the C value on the current lanthanide oxide correction page. This method worked fine in 90% of the analyses, but in 10% it produced horrible results with large depletions of several lanthanides and even large negative concentrations. PerkinElmer was contacted and data sent to them, and they contacted Sciex in Canada. The answer is that, for reasons I cannot fathom, the the Elan software does not always do the corrections in the same sequence. If The Mass 8 equation is not evaluated first, all the rest of the correction equations have the wrong Mass 8 values and yield incorrect results. The current lanthanide oxide correction page solves this problem in a not very elegant way by having the correction vactor C typed into the equation for each analyzed isotope.

 

Table 4 (disposessed). Interference correction equations including isotope overlaps (discussed here) and the oxide interference corrections. Mass 8 is simply a place in the data table where the correction factor C is kept for use by all of the other equations. In red is the numerator of Equation 2, and in blue is the denominator of equation 2. The part in red should be determined prior to each analytical run for lanthanides.
Element Mass Isotope overlap corrections Oxide interference corrections
- 8   - mass 8 + ((measured 158Gd/146Nd ratio) / 0.02540)
Ba 137    
La 139    
Ce 140    
Pr 141    
Nd 146   - ((mass 8 * 0.00002) * 137Ba)
Eu 151   - ((mass 8 * 0.00132) * 137 Ba)
Sm 152 - (0.00805 * 158Gd) - ((mass 8 * 0.00167) * 137 Ba) - ((mass 8 * 0.00002) * 140Ce)
Gd 158 - (0.00402 * 163Dy) - ((mass 8 * 0.00329) * 140Ce) - ((mass 8 * 0.00058) * 141Pr) - ((mass 8 * 0.02540) * 146Nd)
Tb 159   - ((mass 8 * 0.00014) * 140Ce) - ((mass 8 * 0.00004) * 141Pr) - ((mass 8 * 0.01174) * 146Nd)
Dy 163   - ((mass 8 * 0.00041) * 146Nd) - ((mass 8 * 0.00235) * 152Sm)
Ho 165   - ((mass 8 * 0.00010) * 146Nd) - ((mass 8 * 0.00222) * 152Sm)
Er 166   - ((mass 8 * 0.00560) * 146Nd) - ((mass 8 * 0.00119) * 152Sm)
Tm 169   - ((mass 8 * 0.00018) * 152Sm) - ((mass 8 * 0.00067) * 151Eu) - ((mass 8 * 0.00002) * 158Gd)
Yb 174   - ((mass 8 * 0.01256) * 158Gd) - ((mass 8 * 0.00001) * 163Dy)
Lu 175 - (0.00594 * 178Hf) - ((mass 8 * 0.00073) * 158Gd) - ((mass 8 * 0.01235) * 159Tb)
Hf 178   - ((mass 8 * 0.00677) * 163Dy) - ((mass 8 * 0.00004) * 166Er)
Ta 181   - ((mass 8 * 0.00012) * 163Dy) - ((mass 8 * 0.00655) * 165Ho)

 

Kurt Hollocher

Geology Department

Union College

Schenectady, NY  12308

U.S.A.