170135_inorganicventures_flipping

16.6 ICP-MS Measurement

Isobaric Interferences:

• Isobaric interference is a result of equal mass isotopes of different elements present in the sample solu6on. (Low (R=300) resolu6on instruments cannot dis6nguish between the isotopes.) • This is analogous to direct spectral overlap in ICP-OES. • There are a number of monoisotopic elements. There are no elemental singly charged isotopes that overlap with monoisotopic elements ( 9 Be, 23 Na, 27 Al, 45 Sc, 55 Mn, 75 As, 89 Y, 103 Rh, 127 I, 133 Cs, 141 Pr, 159 Tb, 165 Ho, 169 Tm, 197 Au, and 232 Th). • Avoid the problem if possible by using another isotope of that element. There is almost always another interference free isotope.

16.7 ICP-MS Measurement

Isobaric Interferences:

• Perform a mathema+cal correc+on. ( If the interference is from an isotope with roughly the same or lower peak intensity, it is possible to perform a correc+on by measuring the intensity of another isotope of the interfering element and subtrac+ng the appropriate correc+on factor from the intensity of the interfered isotope.) • If you are working with an unknown sample composi+on, a semi- quan+ta+ve analysis is suggested with low-resolu+on instruments using a quick scan of the sample and the rather sophis+cated semi- quan+ta+ve programs available on current instrumenta+on. • Iden+fy any background polyatomic species before aAemp+ng a mathema+cal correc+on.