3.4 Stability measurements 63
depending on their mass to charge ratio. In the system used in our laboratory
a Quadrupole Mass Spectrometer is installed. The system exploits a Radio
Frequency, RF, quadrupole eld, created by four rods, to lter the ions. The
ltered ions are nally detected and a signal can be analysed by the software.
The raw data for ICP-MS is therefore a set of intensities for each mass to
charge ratio, but with calibration runs of known standards the intensities can
be converted into concentrations.
It is a highly sensitive technique where most elements can be analysed down
to sub-ppb (part-per-billion) levels. An overview of the detection limit for all
the elements can be seen in gure 3.14. In this project mainly Mn, Ti and Au
have been measured, all of which have detections limits below 10 ppt (partper
trillion). The instrument used for this project was from Thermo Fisher
Scientic, the model iCAP-QC ICP-MS. For each measurement a calibration
with three known concentrations was carried out.
Figure 3.14: A periodic table specifying the detection limits of ICP-MS for each
element in the periodic table. The dierent colors indicate the detection limit, while
white indicate that ICP-MS is not suitable for detection. Figure taken from 206.