Custom field: Peak Lambda Max.

balu1978

Dear Sir, 
I have a spectrum from 200 to 300 nm. Can I extract a limited range (265-280nm) as a derived channel and get the lambda max of this channel? I tried several versions of custom fields but I couldn't do it. Is it possible in some way?
Many thanks for your help.

Empower2019

I dont think you need a CF for this. Create a derived channel using the "Timed Wavelength" PDA option from the dropdown list in the Derived Channel first tab. Pick a start and an end wavelength, call the derived channel a suitable name and then apply method set on an injection. Search in 2D channels tab for the derived channel and add Peak Lambda Max option to the peak review window and this will show the lambda max value for each peak in this channel. 

balu1978

Yes, you're right, but I would like to create a Pass/Fail judgement CF too. There is 2 lambda max in the spectrum and I need only the second between 265-280 nm. That was the reason why I need help. Do you have any idea? Thanks for all

Empower2019

Yes, you could create a peak, bool CF for this but are you just looking for the 265-280nm lambda max value to be returned? I presume you have your normal channel of data and this derived data with the 265-280nm channel, and you only want an answer if the peak lambda max is from the derived channel? Can you explain a bit more your calculation. 

balu1978

Yes  I have the normal spectra between 200-300nm, and derived channel from 265 to 280 nm. I need the lambda max of the derived channel but it seems that Label.Injection.Channel(Peak Lambda Max.) syntax doesn't work. The normal spectra has 2 lambda max, and I need the second, the little one to further CF calculation.

Empower2019

I tried the syntax on some PDA data and it worked for me. My Label was U1, one injection, channel name (the name of the derived channel, make sure you type this exactly as you named it when you derived it in method set) and the field:

U1.%.PDA Derived(Peak Lambda Max) (name of my CF was Peak_Derived)

My search Order was Result Set Only so be advised you need to generate a result set to see results. 

balu1978

I tried your solution on caffeine data, and doesn't work for me. I attached some pictures as a pdf file, I'm sure, that the issue is by me, but I can't explain what can cause it.
1. Sample set label: S0501
2. Method Set: Range273; Derived Channel from 265 to 280
3. CF: HK_LMAX1; S0501.%.Range273(Peak Lambda Max.)
4. After reprocess tha result is nothing. The channel name and derived channel is OK (2D channel tab page), but no result (peak tab page).

I do something wrong, but I haven't any idea. If you have any observation, please let me know. Thank you so much for you help.

Empower2019

I actually made a timed wavelength derived channel and not total plot, as total plot will return the average absorbance over the stated wavelength region, so make sure that's what you need.

It wont affect the formula either way as I checked with both timed wavelength and total plot as my derived channel and I got results for both when I processed the sample set. It must be something missing in your sample set- is your label definitely S0501 as numbers and not the letter O? When you process the sample set, are you using "Acquisition Method Set" option? Is there definitely a processing method associated with the derived channel in your method set, double check that? Are you selecting the correct method set? Maybe process with the "Use selected method set" option and then pick your method set from the drop down list. Don't process the sample set with the last option of "use specified processing method" as this wont work with 3D PDA data. 

Is the processing column set to Normal or if not the correct label associated with Quantitate? Is the name of the channel in your CF formula definitely correct? If even a space is off or different, it wont work. 
If I managed to do this with both derived channels, it can definitely be done. The answer lies in your sample set/labels or the way your processed the sample set. Remember, unless a result set is generated, no results will be visible. You need to process a sample set to get a result set and not just save results in the review screen as you process.