Can you compare data between 2998 PDA and 2489 UV/Vis detectors? - WKB16155

ENVIRONMENT

• Empower
• 2489 UV/Vis Detector
• 2998 Photodiode Array Detector
• ACQUITY UPLC PDA Detector
• ACQUITY UPLC Tunable UV Detector

ANSWER

No, you cannot. Some of the reasons are as follows:

1. The 2998 and the 2489 use different detection measurement.  
The 2998 uses the formula:
Absorbance = -log [( Sn- Dn)/( Rn- Dn)]

where:

S = signal obtained during sample analysis 
D = signal obtained during dark current measurement 
R = signal obtained from reference spectrum 
n = diode number

The 2489 uses direct absorbance measurement (without any subtraction) by default.

2. The bandwidth on a 2489 (e.g., 5 nm) is different than the spectral resolution on a 2998 (the closest you can assign is 4.8 nm).

3. The detectors' flow cell and light alignment are different. The 2489 uses taper-slit, and the 2998 uses taper beam.

4. There is also a difference in the proximity of the flow cell to the light source. The lamp is much closer to the flow cell In a 2998.

Because of these differences and others, you cannot directly compare the data from a 2489 with that from a 2998.  
 

ADDITIONAL INFORMATION

If the peaks look different on the 2489 verses the 2998, try changing 2998 bandwidth to 4.8 nm.