Tip #270: Exploring the difference between amount and concentration and the influence of injection volume on quantitation

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In this week’s tip for Empower Chromatography Data System (CDS), we continue our series on calculating Amount/Concentration and we will look at the difference between Amount and Concentration, as well as the influence of injection volume on quantitation. In last week’s tip, we explored Calibration Curve parameters within the Processing Method which affect the calculation of Amount and Concentration, Tip #269.

Empower calculates both Amount and Concentration for standards and samples.

• If you enter values for the standards in the component editor as amounts, Empower calculates concentration as the amount/injection volume.
• If you enter values for the standards as concentration, Empower calculates amount as concentration x injection volume.

Please Note: Units entered in the component editor do not affect the calculations and you should check your SOP for the required units. Once the sample set has been processed the samples are quantitated by reading the response from the calibration curve and determining either the corresponding amount or concentration for the components. Empower will calculate both amount and concentration for the components.

Let’s get started.

Step 1

Looking at the result for the sample from the end of Tip #269, we see the amount for Caffeine was determined to be 0.040102. The concentration is calculated as the amount divided by the injection volume, which is 2, therefore, the concentration is 0.020051. In this case, all standards and samples were injected at 2 microliters, and the amount in the standard vials varied in increasing amounts from standard 1 thru 5 (figure 1).

figure 1

Step 2

In the Paraben sample set, we have a stock solution at a concentration of 0.167000 mg/ml and we vary the injection volume for the standards (figure 2).

figure 2

Step 3

The Processing Method indicates that the calibration curve will be plotted as amount on the x-axis and area on the y-axis (figure 3).

figure 3

Step 4

The calibration curve is generated once the Sample Set is processed (figure 4).

figure 4

Step 5

The amount and concentration of the components have been calculated for the sample (figure 5).

figure 5

It’s that easy!

Final Note: This can be done with either the Pro or QuickStart interface.

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Next time in Empower Tip #271– we will pause the series on how Empower calculates Amount/Concentration to answer a reader question.

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