Empower Tip: Custom Fields

In this tip, we explore a Custom Field solution for peptide mapping.

It is common to use a mass detector when doing peptide mapping methods. We want to compare the base peak value to the expected mass for each named component as a way to make sure the peaks are properly identified. Our goal in this case is to create custom fields that give us a pass/fail on a peak-by-peak basis and an overall pass/fail for the sample.

Let’s see how it is done!

In this example we have two named peaks and we can see the base peak for each.

The Components tab in the Processing Method displays the named peaks.

The MS Expected Mass tab in the Processing Method displays the expected masses for the two peaks. In this case we are doing Component-based processing.

A Peak Custom Field, data type Real instructs Empower to determine if the base peak is within a plus/minus of the expected mass.

A Peak Custom Field, data type Boolean instructs Empower to determine if the outcome of the of the Boolean expression in the previous custom field returns a ‘0’ or ‘1’. If it is equal to ‘0’ the peak fails and if it is equal to ‘1’ the peak passes. This provides a pass/fail on a peak-by-peak basis.

Finally, a Result Custom Field, data type Boolean instructs Empower to multiply the outcome of the Custom Field in Step 5 for each peak. If all peaks pass, then the product of multiple 1s is 1 and the sample passes. If one peak fails, the product of 0 x 1 = 0 and the sample fails.

In the first example both peaks pass, therefore, the overall sample passes.

In the second example one peak fails, therefore, the overall sample fails.

It’s that easy!