Chromatography Forum

Hi All

Thanks in advance for any help you can offer.

We use chemstation / chemstore at work (no choice in this). I have been playing with the custom calculations but I can't figure out how to enter a calculation that works out a result for more than one line in a table.

eg (table)
batch area assay
1 xxxx
2 xxxxx etc Where the assay result is calculated for each batch. I know how to do it for one batch at a time, but would like to be able to take the stds and sample data, and work out the assay.

I worked out a basic calculation to be

sample table.area * std table wt *all dils istds etc /mean (std area from table)*sample wt

if i remove the sample bits or enter them manually it works, but if i use a table containing data for all batches/injections, i get no results

I know you can do this in chemstation using the cal tables, but for technical reasons need to be able to do this another way. Basically, the std contains peaks that need subtracting from the impurities in a second std before working out the impurity results (if that makes sense)


Also when I create a table i always get three lines for each section ie

inj name area
1 A xxxxxx
1 A
1 A
2 A xxxxxx
etc

But 2 of the 3 lines are always empty except for names and location data. How do I prevent this?.

While I am at it, is there a wildcard option for fields....like in linux where you can search for *.txt and get all txt files as a result?


Thanks again

Are you using the Sequence Summary Report function? We use that to automatically calculate the results for us in percent, and to calcualte the system suitability data, all automatically.

Hi!

It's a little bit fuzzy. Are you calculate in ChemStation or Chemstore?
What is this "table", the sequence table?
Or is it an external excel sheet?

Did you work out a calculation, so you are in macro programming?
Inside the ChemStation multipliers or dividers only usable in ESDT% or ISTD% calculations.

I'm confused.

OK will explain some more......

We do use chestation to work out some of our results......what I am trying to use is chemstore, using the custom calculation.

The tables are what you get in the custom calc.

The reason I want to do it this way is due to the specifics of this one test.

In short the method is rubbish, but licensed so nothing we can do to change it. We us 2 standards, one for the assay (in duplicate with a standard recovery worked out using both, i managed to do this using the custom calc, but all my tables allways have 3 rows for each entry, see first post)

The second standard is for impurities, you add 3 impurities, plus some of the compound standard used for the assay stds. This means when you inject them you get the sample peak plus the 3 impurities. Although not specified, I assume this is to show seperation as 1 imp is very close to main peak.

The issue is that the compund std also contains some impurities, typically 0.7% to 0.3%....So this makes the peak areas of the impurities in the Imp std high. So we normalise and subtract the peak areas from an average obtained from the assay std injections (of the impurities).

What I was trying to do was write a calculation in chemstore to work all this out for multiple batches (at once) and print them on a report, with the peaks and other data.

I am pretty sure I can get a calculation working that does this for one batch at a time, by excluding all other batches in chemstore review window and running the calculation / report for each one. This would still be easier and quicker than manual calculations, just not really as elegant.

The data I am using to play with isn't the best as i didnt enter any amounts in the sequence before the run....and entering during reprocessing does't get picked up.

The problem I have is my computer language isn't very good (I am very good with hardware, and point and click programs), so i am having to rely on the wizards to build the data.

As I said i managed to take the areas for the main peak from 5 std A's and 2 std B's, average the areas, and use them in the following calculation
in chemstore (using a custom calculation)

Area A * wt B* 100 / Area b *wt A


The 3 lines in all tables I use for custom calcs is annoying, but doesn't appear to change the results....its only names that get repeated, peak areas and weights appear once, and the mean results appear to be correct


Hope that helps explain what I am trying to acheive (basical do with chemstore custom calc what can be achieved using chemstation, and work out a result for multiple batches in one got)

ps sorry for the txt wall, not the easiest of things to explain in a few short lines

OK think I may know why i get 3 lines for each injection in the custom calc tables.....we use 3 detection wavelenghts, so need to add an extra filter, to only select the results for the correct wavelenght.


I think I may be able to solve my other issue by transposing the colums, after doing the area / wt for each batch, transpose that column, and use the the calculations on it

Hi!

Basically I have no idea what and where it is "custom calc tables". Maybe we have a different version of ChemStation.
Nevertheless I'm happy you can solve the problem by yourself.

OK Solved this issue...

If you want to find the custom cal, check chemstore......