Helpful Empower Tools: Variations in Peak Retention Time - Tip338

Last updated
Save as PDF
Share
1. Share
2. Tweet
3. Share

Article number: 266842

OBJECTIVE or GOAL

Employ the Empower tools that assist with variations in peak retention time.

ENVIRONMENT

Empower
Empower Tip of the Week #338

PROCEDURE

It is not unusual to observe slight variations in peak retention time from injection to injection. If the variation in retention time becomes excessive, it can result in peaks not being identified properly and, consequently, components not being quantitated. Tools in Empower can help with variations in peak retention times.

STEP 1
We start with a standard containing four components, all identified properly (Figure 1).

STEP 2
In the sample chromatogram, Peak #3 has shifted and is not identified. The peak type is Unknown. The peak table also shows that Peak #3 is missing. Clearly, we see the peak at 8.033 minutes, but Empower has not identified it (Figure 2).

STEP 3
If the peaks are well separated, we can increase the retention time windows around the peaks, which would compensate for the shifts in retention time (Figure 3).

STEP 4
Another tool we have is the Retention Time Reference peak, or RT Reference as it is called on the Components tab of the Processing Method. A Retention Time Reference peak must be in every chromatogram and, ideally, should be well separated from the rest of the peaks. As long as Empower identifies the reference peak, it will properly identify any peaks referenced to it. In this example, we select Peak #2 as the reference peak (Figure 4).

STEP 5
This is the calculation for the temporary retention time used for peak identification. This does not change the expected retention time listed on the Components tab of the Processing Method (Figure 5).

STEP 6
Substituting in the real numbers: (4.842 / 4.889) x 8.146 = 8.068. The temporary expected retention time for the peak is 8.068 +0.091 minutes. Now, the peak at 8.033 minutes falls within the new retention time window and is identified properly (Figure 6).

ADDITIONAL INFORMATION

This can be done via the Pro or QuickStart interface.