Chromatography Forum

I know you can create a custom field to get the AVERAGE area over 2 injections of a sample but is it possible to create one that calculates the difference between the area of 2 injections?
I have a standard that is injected twice after my samples and my criteria is the % Difference cant be more that 2%. Any ideas?

Hi EmpowersBane,

Yes, there has to be a way to do this via InterSample Calculation. One of these days (or weeks, I guess) I really need to re-learn what I used to know and learn a heck of a lot more about Custom Calculations. So much horsepower I (or any Empower user) has that goes mostly to waste. I hope someone has an answer. There's a company in Berlin, Germany, Beyontics. They sell a Really Nice Empower manual (slanted to Empower 3) as well as one for Custom Calculations alone...I know the former one as I've purchased it. Maybe the Custom Calcs one is worth looking into? I'd do it myself...my personal funds are low now, sadly.

Thanks for the reply mattmullaney,

Is the Empower book from Beyontics worth purchasing? Do they cover the usual like report methods, changes from Empower 2 and running samples etc? I know what you mean about forgetting. I think its something like Highest Area (from the 2 injs) divided by Lowest Area x 100 -100 to get the percent but I'm not sure do I put it in CCalRef or CCompRef!

Hi EmpowersBane,

For me, yes, it was absolutely a worthwhile purchase. My copy of the book is at work at the moment...I will respond again with a list of the table of contents. This will help you see what is inside a bit, I think.

Unfortunately, I don't think that a direct answer to the question you're asking is in the text that I have--maybe it would be present in the other text Beyontics sells...or certainly in the one-day course Waters offers. No one seems to have money to go to the training these days. Waters does have some online courses, these may be too brief in nature to really help.

I think it's already in there. When you review your standard curve, there's a deviation column. I think that's all you may need - current std deviation from running average (confirm the math on this). You may need to multiply by 10 to make a % of it.

Ah thanks Ill double check the maths on that one. I saw a very long custom field for this on one of the training websites but it was almost like an IF function in Excel and gave 2 scenarios depending on if the area of the first injection was larger than the second.
Is it possible to create a custom field multiplying the std deviation by 10 and throw it into a report method?

Hi ,

Worth trying multiple of 10

Try this is a custom field
Field type : Peak
Type : Real (0,0)

Area Ratio = (Area/CCompRef2(Area))*(CConst1/Cconst2)

For people who know more, I checked online and they suggested the following custom filed for calculating the percentage difference between area over 2 injections, bearing in mind the first area may be lower than the second.

Does this look right:

% Diff = Highest Area/Lowest Area *100 - 100.

Custom Field:

GT((.1.(CCompRef1[Area])),(.2.(CCompRef1[Area])))*((.1.((CCompRef1[Area]))/.2.(CCompRef1[Area])*100)-100)+ GT((.2.(CCompRef1[Area])),(.1.(CCompRef1[Area]))) *((.2.((CCompRef1[Area]))/.1.(CCompRef1[Area])*100)-100)

Hi ,

Maybe a long-wided way of doing this but if it works..all good
Could you also simplify by using ABS function ?

Hi EmpowersBane,

My apology for interrupting; I am late to respond, good to see that folks are suggesting solutions. For the Beyontics book I have, "Empower 3, A Compact User's Guide," here is what is inside. Note, this is for Feature Release 2 (FR2), from 2015.

Intro
Editions and Network Architecture
QuickStart Interface
Project Window
Data Acquisition
Data Processing
Reports
Data Import and Export
Configuration Manager
Custom Fields

Overall the book is very good for a beginner or as a refresher...and a pretty fair reference, I'd think, for a moderately experienced user. Beyontics sells a separate text on the Custom Fields...this you may be interested in. Beyontics is in Berlin, Germany. I like the book I have a lot.

Thanks a million for that mattmulaney I really appreciate that. That manual sounds like a fantastic guide/refresher for Empower 3, particularly when its laid out in logical order like that. I looked into Beyontics and yes,I saw the custom field book they offer, which might be worth getting as well because there is so much to it you could nearly do a masters on it!

Thanks again for the information.

I like the book I have...just no funds for the Custom Fields book.

Hi ,

I have both books mentioned

Very useful as reference and custom fields manual I would recommend

@ ydna1977,

I will continue to save my money for the purchase of the Custom Fields text. My thanks for your endorsement!