Tip #42: Calculating impurities in samples (Part 3)

Welcome back to Get Empowered! In the last tip-of-the-week blog for Empower Software, we discussed how to calculate impurities in samples.

• Tip 40: Calculating unnamed impurities in samples (part 1)
• Tip 41: Calculating impurities in samples by % adjusted area (part 2)

This week we continue the discussion and look at another example (Part 3).

Previously, we wanted to express the impurity response as % adjusted area while excluding certain peaks such as a system peak from the calculation. In this example, we are going to express impurity response as % area against the main peak. We could create a custom field to make the calculation or we could use the features in Empower Software that are designed just for this purpose.

Let me show you how.

Step 1

Let’s start by bringing a sample set into Review, open the processing method, click the processing method tool, and click the Impurity tab (Figure 1).

Figure 1

Step 2

For the Impurity Response, select % Area Against Main Component from the drop-down list (Figure 2).
The calculation is (area of peak / area of main peak) x 100.

figure 2

Step 3

Now let’s select the name of the main peak from the Main Component drop-down list (Figure 3).

Figure 3

Step 4

Return to the main window and click quantitate. The original %Area is next to the Impurity Response (Figure 4).  (I did adjust the precision for the %Area field from 2 to 3.)

Figure 4

If we look at Impurity E the original %Area is 0.561% and now, compared to the main peak, it is 0.568% – which makes sense, since the area of the peak is now compared to the area of the main peak, which less than the total area for all peaks. (Hint – remember that you can see the total area by going to the Results window within Review and check the middle table called Chromatogram Result.)

It’s that easy!

Final note:

This procedure can be followed using the QuickStart or Pro interface.

Please rate this Empower Tip of the Week

Next week in Empower Tip #43: Calculating Impurities (Part 4), Working with thresholds

More resources:

• Want to learn more? Check out our Empower training courses and eLearning
• Get the latest Empower projects, options, and more. Check out the New Marketplace
• See all of our tips for using Empower CDS Software
• Comments? Connect with at #EmpowerTips or @WatersCorp on Twitter.
• Submit an Empower 3 Review with Select Science.  Write a review.