Chromatography Forum

As I've mentioned, I'm trying to learn/use ChemStation coming from Empower.

My latest challenge is multi-level calibration Curves... In Empower I create an Integration method with the compounds names and retention times, Curve type, fit , weightings etc and if I want to average by level.

In the sample set I enter that it's a standard and the standard amounts for as many analytes as I want, and if I care, level IDs...
I enter the analytes and their amounts in a single 'spreadsheet' all at once which is very easy/fast.

In Empower levels are used to optionally average replicate standards for each amount, not necessarily ID different amounts and don't HAVE to be used. If you don't enter them and specify Average By Level then each sample/Amount pair is an independent data point for the regression.

At the end of the run, if I made any errors is setting up the Sample Set, I can change Unknowns to Standards Or QC's etc. and enter the amounts. In fact sometime in a hurry to get the run started I don't enter amounts (when using new standards solutions) until after the run. As i don't make new standard solutions for every run I use a Sample Set to make a Sample Set Template with so I don't have to reenter amounts (which vary a little because of weighing)

To do the calibration (among other ways) I can just process the sample set (or pick, the individual Channel data from a table/spreadsheet that has all data for all channels with sample name, date acquired, Sample Set name etc, which I can filter on any column as a batch) and it creates separate calibrations curves for each analyte ... I don't have to even look at the chromatography (though I can do it that way if i want) or load individual 'levels' from a sample set to do the calibration...

Then as long as I don't do another calibration with that integration method, I can keep processing samples with that integration method and it will keep using that set of calibration curves to calculate unknown amounts.

The whole process is quick and easy...

I did a run on Chemstation with 6 different standard concentrations, with 3 analytes in the standards (all analytes are not at the same concentration in the same standard solution).

First, because of a mistake setting up the sequence, I need to change one of the vials that was run from a Sample to a Standard... I can't seem to find a way to do it... i it possible? If so how?

Looking at the Agilent documentation, doing multilevel calibration in ChemStation looks amazing cumbersome and time consuming in comparison to Empower... and it's also not obvious how to simultaneously do multiple analytes as independ and calibration curves at the same time. I have to load individual signal to Calibrate? Can I do all 3 analytes at once, or do I have to go through that 3 times?

It's can't be that slow/cumbersome ... am I misunderstanding things?

Thanks,
- Karen

First, because of a mistake setting up the sequence, I need to change one of the vials that was run from a Sample to a Standard... I can't seem to find a way to do it... i it possible? If so how?

Go back into Sequence, Sequence Table. On the line you want to change, scroll to the right, in one column it will state "Sample". Click that and a little box will open giving you the choice of calibration standard or control sample as well. Then you can save the Sequence, switch to "Reprocessing Only", check the little box to the left of that to use Sequence table changes, and Reprocess.

When we do the automatic data calculations, we have an inital row in Sequence Table as Calibration, and Replace for response factor, so previous calibration date (like from last month) is not used. The next line/row would be the same except that we select "average" which averages the calibration data from the last injection detailed as replace with all the calibrations detailed as "average", and that average is used for all data calculations until any later calibration standard injections.

When we do the automatic data calculations, we have an inital row in Sequence Table as Calibration, and Replace for response factor, so previous calibration date (like from last month) is not used. The next line/row would be the same except that we select "average" which averages the calibration data from the last injection detailed as replace with all the calibrations detailed as "average", and that average is used for all data calculations until any later calibration standard injections.

Ok.. Thanks... so I have to process to edit the sample data that was originally entered.

Not intuitive but as Chemstation is not built on a database I can understand why it works that way even though it did not have to be. For me, processing to calculate results is logically different from editing entered sample data and so I did not make the connection.

But how so I handle standards standards with 3 different components for 6 concentration levels when the concentration of each analyte are not the same in each standard solution? Can it be set up to create 3 independent calibration curves and then apply those 3 curves to single injection to produce (and report) results for all 3 analytes all at once?

This assay is supporting 2 different projects that have some overlap in analytes and I can be running lots of samples from either project or both projects, in the same sequence and any sample can have any combination of or none of the analytes.

As i said I find it quick and easy to do that in Empower and it literally takes only a few seconds post run (asumming I entered the standard amount up front or using a curve set from a previous run), but it's awfully confusing to me in ChemStation and not clear to me if it can be done.

- Karen

There is a way to create a calibration table "manually" if you have different concentrations for different analytes in your ical.

Create a new calibration table, create three analytes, and insert 6 levels to each analyte. You can manually type in retention times, concentrations (analytes need not have the same concentrations), and the corresponding areas. You may have to print a report for each calibration run in order to get the areas so you can type it into the calibration table (only need the correct retention time inserted into the table for area counting). Then after the areas are inserted into the calibration table, save and reprocess to check your work.