Tip #79, Reader question: How do you calculate the height of the valley point between two fused peaks?

Welcome back to Get Empowered! In the last Empower tip-of-the-week post for Empower CDS Software, we answered a reader-submitted question and learned how to quantitate impurities against the main component. (Tip #78)

(See the link at the bottom of our post to see previous questions, ask your own question, or to provide a tip of your own!)

In this week’s tip, I’ll answer a question as a follow-up to Tip #74 on using Empower’s System Suitability option to calculate the ratio of peak to valley height when there’s a valley between the chromatographic peaks.

Question: How can we calculate the height of the valley point between two fused peaks?

Another great question.

Let me show you how it is done.

Step 1

If we recall from Tip #74, the ratio of peak height to valley height is calculated as start p/v or end p/v.  The height of the relatively big peak at 1.005 minutes ends at a valley point, so Empower Software reports the end p/v.  The peak at 1.192 minutes starts at a valley point so Empower reports the start p/v (Figure 1).

Figure 1

Step 2

If we solve for valley height, the calculation would be valley height = peak height/start p/v or peak height/end p/v (Figure 2).

Figure 2

Step 3

This is a simple peak custom field in Empower (Figure 3).  (You can make a similar one substituting end p/v.)

Figure 3

Step 4

We see the result of the calculation in the peaks table in Review. The valley height is the same regardless of which calculation we use (Figure 4).

Figure 4

It’s that easy!

Final Notes: 

1. We will do a series of Empower Tips on Custom Fields later this year… Stay tuned!
2. This procedure can be followed using the QuickStart or Pro interface.

Please rate this Empower Tip of the Week

Previous questions we’ve answered:

• How can I calculate the ratio of peak height to valley height when I have a valley point between peaks?
• Why is the retention time of my peak slightly different than the retention time of the UV apex spectrum for the peak?
• How do you calculate impurity response when there are two APIs in the sample?
• How do you summarize specified and unspecified impurities in a sample and quantitate them against the main component?
• How do you quantitate impurities against the main component?

Next week in Empower Tip #80 – How to use the Result Audit Viewer

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