With ACQUITY UPLC PDA Detector, the area value increases as the flow velocity decreases. Is this abnormal? - WKB224783
ENVIRONMENT
- ACQUITY UPLC PDA Detector
- 2489 UV/Vis Detector
- 2998 Photodiode Array Detector
- ACQUITY UPLC Tunable UV Detector
ANSWER
No, it's not abnormal.
For PDA (UV) detectors, the longer the sample stays in the detector cell, the larger the area value.
The reason is that the sample repeatedly absorbs and releases energy during the time it is in the detector cell.
If the flow velocity is high, the time will be short, but if the flow velocity is slow, the time will be long, so energy will be absorbed and released repeatedly, and the peak absorbance AU value will increase accordingly.
For this reason, the peak height and the area value also increase.
The figure above is an example of measurements with two peaks performed at 0.3 (red), 0.4 (blue), and 0.5 mL/min (green), respectively.
Area value of peak at 7.7 minutes (flow rate 0.5 mL/min): 61843
Area value of peak at 8.7 minutes (flow rate 0.3 mL/min): 104818
Even with the same peak, the area value increases about 1.6 times when the flow velocity changes from 0.5 to 0.3 mL/min.
ADDITIONAL INFORMATION