# Use Custom Field to calculate the Relative Deviation between two injections for every sample

How can I use custom field to calculate the Relative Deviation between two injections for every sample. I try to calculate Average firstly by using the formula: U%.%..AVE(Area), but feedback every injection Area value rather than two injection.Also, I put Summarize Custom Fields Function into Sample Set, but didn't work.

• Use the syntax SAME for the Intersample Custom Field Calculation, and use the same label for each sample. For example, if you have 10 samples, label the first 2 as U1, the second 2 as U2..etc, the same logic if its just 2 injections of one sample- then your formula becomes:
SAME.%..%RSD(Area), and make sure to put Summarize Custom Fields as the last line in your sample set. Then when you process a sample set to generate a result set, you will get values for the RSD of the areas across each set of samples.
• Thanks for answer but something's wrong.
I've tried your way(including labeling and changing Sample Set), it feedback value: 0.00.And I replace %RSD to AVE, it calculated just one injection. Besides, there's another field I changed.(See the picture)

When I processed datas in Review Main Widow, the application crashed without warning or error.
Is possible the calculation too complex and lead to crash?
• Hi, no the calculation is a very simple one so it wouldnt be complex. I tried it out on some example data and it worked fine for me. Are you running separate injections of the same sample on different rows or vials or is it 2 injections from the same vial?
I had a sample set with 2 samples, 3 injections per sample. So i labelled the first sample U1 and the second sample U2. My formula was a peak, real custom field:

SAME.%..%RSD(Area) search order Result Set Only. I processed a sample set to generate a result set and the answer populated in the result set. Make sure your sample set has Summarize Custom Fields line as the last line in sample set and this is set to processing of Normal. if it worked for me, Im sure it will work for you as well.
• Hi, it's no longer output "0.0", but %RSD of two injections wasn't equal. The experiment is quantitative experiment. And calibration curve is Amount against Area (See the picture). Is there something wrong in setting?
• Set the search order to result set only, result set first will still search outside of your current sequence.
• as shaunwat says, result set first with an intersample summary function like AVE, MAX. MIN. PROD or %RSD will search for all the results in the project including the ones in your current result set and this will affect the final result. Typically, Empower crashes and burns if there are several samples of the same label and gives a result just generated before it crashed, which wont be accurate.
Result Set Only will confine the search to your generated result set.
• Hi, this time, this custom field got no figure (see the pictures). Can anyone fix it?
• Thats strange, I dont see anything wrong in your sample set layout. Did you process the sample set to generate a result set or did you process from the Injections or Channels tab? Result Set Only will only work if all the results are contained in one result set. Another thing is to make sure you process this sample set with the acquisition method set or a specified method set and not with just a processing method. If you only use a processing method, it will ignore Empower functions such as clear calibration and summarize custom fields. Make sure to process the sample set with a method set (that contains a processing method within it) and that should work for you.
• Hi, I see the difference between us. I process data from the Injections or Channels tab, and get Results rather than Results set. In this situation, Custom Field will not work? I hope I can get Custom Field calculation while processing data interactively.
• edited September 2023
Yes, the search order is the reason you didnt get results. Its cleaner to process a sample set to generate a result set. That way, all the results are bound together. If your policy forbids this, the only way to get it to work when processing from injections or channels is to change search order to result set first, highlight all the relevant channels together (generating results one by one wont work as you are asking Empower to consider multiple channels with the same label), so either select all the B01 together and process them from channels or select the whole set from Channels and process that way.

Also, its very important to use different labels per sample set if processing from Channels since Result Set First will search the whole project for that label and therefore include all values from previous B01 etc results which will skew your results and often lead to no results as Empower crashes trying to find all previous results. In that case your labels need to be unique such as B1 then next sample set B11, B111 etc!

As i said, much cleaner to process a sample set with a method set to generate a result set. The custom field will work if you do it that way.
• Thanks a lot!! And further more, there are some questions:
①How can I calculate RSD% among 5 injections of Controls(as system suitable test, SST.)?
②Also, how to calculate RSD% between 1 injection(as system validation, SV.) of Control and 5 SST injections?
③How to NOT to calculate Blank(as inject sample)in Custom Field? (just calculate unknown sample.)
In my Sample Set Method, they are in the following order:
Vial1: Blank(2 inj.),
Vial2 to Vial6: Standard 1(2 inj.) to Stardard 5(2 inj.),
Vial7: SST.(5 inj.),
Vial8: Sample 1(1st inj.),
Vial9: Sample 1(2nd inj.),
Vial10 to Vial13: Sample 2...etc.,
Vial7: SV.(1 inj.),
(End of Set: Conditional Column: Shutdown)
• 1. To calculate %RSD amongst the 5 injections of control, use the label for these 5 injections in your custom field formula, I presume you are calculating the %RSD of Area? If not replace with your desired field: SST.%..%RSD(Area) Search Order Result Set Only, process a sample set to generate a result set and you will get result in your result set.

2. To only pick the 1 injection of SV and the 5 injections of SST, you need two custom fields. The first one is a simple: Sample, Text custom field and call it something like CF_Ref and in the sample set against the 5 injections of SST make sure to add in the text Reference (or whatever is convenient) against those samples. Put in N/A for all other entries in sample set. Then create a second Peak, Real Custom field, search order Result Set Only and the formula is:
%.%.SAME.%RSD(Area*(EQ(CF_Ref,"Reference"))).
This CF will only calculate the %RSD of Areas in the sample set where the CF_Ref is populated with the word Reference, so in your requirement the SST and the SV rows. This is a flexible CF where you can move around the word Reference according to your needs, so for example if you wanted only the %RSD of Vial 8 and Vial 9, you would put Reference in those rows of the sample set, process your sample set and then the results would be generated in the result set.

3. I dont understand you here, can you elaborate on what exactly you are looking for in terms of the blank?
• Hi, Empower2019
1.-2. If I don't process whole Sample Set(to get a Result Set), just process partial sample, can I use your method to get RSD of SV&SST sample?
3. The blank sample means Blank control sample, which I don't want to calculate in Result Custom Field.