How can I use different elemental composition settings for different compound masses?

You may wish to use different parameter sets for analytes with different properties when carrying out an elemental composition calculation. A good example might be to use one setting for low-mass compounds and another for high-mass compounds, especially given the potential difference in search time and complexity between such species.

As described in the main FAQ guide for elemental composition calculation, the currently selected parameter set will be used to calculate possible molecular formulae for all the currently shown compounds. However, it is possible to search different sets of compounds in different ways by altering which compounds are currently shown, through the use of tag filtering.

You can apply relevant tag filters to groups of compounds, update the filter to show only each group in turn, and apply a unique parameter set for elemental composition calculation to each one.

Example

An example of a representative data set filtered in this manner is provided below.

[1] In this case, all molecules with a known neutral mass are being considered, and that main filter has already been applied. At the Identify Compounds step, Elemental composition is then selected as the search method. Multiple parameter sets have been readied for this search type (e.g. Parameter set 1 as shown below).

[2] Compounds are ordered by ascending neutral mass.

[3] Compounds are selected using the table, and tagged into different mass range groups (one such tagging process shown).

[4] Filtering is carried out to show compounds belonging to one of the mass groups. The first parameter set can now be used for an elemental composition calculation, and only these compounds will be searched.

[5] This process can then be repeated by clearing the filter and selecting a different tag group and a new parameter set (not shown, as a repeat of step [4]).