Chromatography Forum

I am running a dual wavelength method (225nm and 248nm) that has a retention time adjustment factor. The retention time of a peak at 248 nm is subtracted from a constant. This number is the adjustment factor. This factor is then applied to all peaks in both channels giving us an adjusted retention time. I have been able to get the adjusted retention time to work for the 248nm channel but have not been able to get it to work for the 225nm.

Custom Fields so far:
Peak Field ..2487Channel 2(MP[RT]) Peak_RT this gives me the RT of my peak

Peak Cconst1-Peak_RT Adjust_Factor this is the adjustment factor

Peak Retention time-Adjust_Factor Adjust_RT this is the adjusted retention time.

Now here is the weird thing, when I process the samples the custom fields work correctly at the 248 channel but the 225 channel the Adjust_Factor column is returning Cconst1. For some reason it is not applying the Peak_RT to the equation.

Thoughts?

Thanks in advance for the help.

Double check the processing method for the channel that is not working... is the ccal ref set as with the other rocessing method?

On a side note, I've never heard of doing this sort of thing. Usually, unknowns are tagged as a function of their relative retention time as compared to a known peak. This minimizes instrument to instrument and run to run variation. Is what you're doing meant to accomplish the same thing?

The same processing method is used for both channels. I haven't tried separate processing methods for the channels, that may be something to try.

I have never heard of it either until I was handed the method earlier this week. In the original post I left out the other custom field of performing the RRT with the new adjusted RT calculated. I am not sure of the point of this calculation as opposed to the regular RRT that you described, but it is a client method that has been used for years so they are not wanting to change it.

Just recently the powers at be decided to move the calculations to Empower to save time on data checking and that is where I come in.

Figured it out.
In the method set where you specify which channel uses which processing method I had channel 1 on top. Channel 1 was being processed before the Adjust_Factor was created in the processing of channel 2. By flipping them and putting channel 2 on top everything works out fine.