2. Particle Compositions on an ICP-ToF

The simultaneous aquistion of elements by an ICP-ToF has major benefits over a quadrupole based instrument. One key advantage is the ability to determine particle compositions. In this example a mixture of gold, silver and gold-silver core-shell particles are analysed, and separated using clustering and compositional filtering.

  1. Download the required data file.

    The tof_mix_au_ag_auag.csv file can be found in the example_2_data.zip archive.

  2. Import the data file.

    In this example we are only interested in the gold and silver isotopes (Ag107, Ag109 and Au197). Using the Data Import wizard, filter out the unused isoptes (transition metals) by unchecking their columns.

  3. Select the Compositions view.

    A detailed description of the view can be found in the Processing Results section. In Fig. 2.1 we can see two clusters, representing pure gold and pure silever particles. The core-shell are fewer in number that the default cutoff (5% of the maximum cluster) so are hidden.

    ../_images/tutorial_tof_cluster_results_1.png

    Fig. 2.1 Composition clusters, only two are visible.

  4. Lower the minimum cluster size.

    The default parameters limit the minmum cluster size to 5% of the total particle count. In this example the number of AuAg core-shell aprticles is small so we need to decrease it. In the graph options dialog, set the Minimum cluster size to 100.

    ../_images/tutorial_tof_cluster_results_2.png

    Fig. 2.2 Three particle compositions are visible, gold, silver and gold-silver core-shell.

  5. Filter results to include only pure gold particles.

    We can use the clustering results to limit our analysis to a single particle type. Open the Filter Dialog and add a cluter filter for cluster index 2 (gold particles), see Filtering for details. The cluster index for each cluster can be found below the pie in the Composition View, as in Fig. 2.2.

    Note

    A similar result could be obtained by filtering for particles that contain no silver (Ag signal == 0).

  6. Switch to the Histograms view.

    The displayed histogram for gold is now free of interfering signals from core-shell particles.

    ../_images/tutorial_tof_cluster_filtered.png

    Fig. 2.3 Filtering (right) has removed the gold signals from core-shell particles, leaving only signals from pure gold particles.