what is the cause for the diffusing peak

[JM]

YM,
It seems the difference is setting of PDA detector and UV. Could you pls check , if you are using any reference wevlength in your PDA?? if yes turn it off and rerun your samples. I have seen if your peak of interest fall between reference wevlength range it will not show in PDA, whereas in UV there is no such setting.

JM

[ym3142]

JM,
Thank you for the asking and I am sorry to be late.
After I check my instrument method setup I failed to see any reference wavelength though I did see "interpolate 656nm". Is this you talking about? Or would you mind let me know how to do the check or turn on/off? Thanks again