# Get Empowered: Review Window and the Processing Method | Tip #41

By October 31, 2017

## Tip #41: Calculating impurities in samples (Part 2)

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

This week we will continue the discussion (part 2).

Have you been tasked with identifying and quantifying impurities in your products? Do you have SOPs requiring numerous calculations for impurities? If so, there are features in Empower that you can use to make your life much easier.

Let’s start with a simple example where we need to express the impurity response as % adjusted area. Empower calculates %Area for every integrated peak, however, what if we wanted to exclude certain peaks (system peak for example) from the calculation? We could create custom fields to make the calculation – or we could use the features in Empower 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 Components tab (Figure 1). The Component Type field can be used to classify peaks that will be excluded from the adjusted total area calculation.

Figure 1

### Step 2

Assign component types as needed; for example, we have a system peak and a formulation peak (Figure 2).

Figure 2

### Step 3

Next, click the Impurity tab (Figure 3). This tab allows you to specify parameters to identify, calculate, group, and set limits for impurity peaks. It works in conjunction with the Components tab.

Figure 3

### Step 4

The Impurity Response defines how impurity values are calculated. Click the drop-down list and select % Adjusted Area (Figure 4).

Figure 4

### Step 5

In the Adjusted Total Area: Excluded Component Types select which type(s) of peaks to exclude for the adjusted total area calculation (Figure 5).

Figure 5

### Step 6

When we return to the main window and click quantitate, we don’t see the results of the calculation because the field is hidden. Right-click on the peaks table, select table properties, and unhide Component Type and Impurity Response (Figure 6).

Figure 6

### Step 7

I moved my %Area column next to the Impurity Response column for better comparison (Figure 7). Impurity B had a %Area of 0.06 and now the % adjusted area is 6.473.

Figure 7

### Step 8

Click the Results tool and look at the Chromatogram Result table. The Adjusted Total Area is a hidden field that you can add to the table. Here we see the comparison of the original total and the adjusted total (Figure 8). (%Adjusted Area is calculated as area of peak/adjusted total area x 100.)

Figure 8

It’s that easy!

Final note:

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

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Next week in Empower Tip #42: Calculating Impurities (Part 3)

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