by
lmh » Mon Aug 05, 2013 9:42 am
LC Chemstation is a little different to GC (although the underlying idea is very much the same). You need to go, in the data-processing review, to the menu "Report" at the top of the screen, and "Specify Report"; this opens a window, at the top right of which is the method for calculating results: by external standard, internal standard, area percent etc. You need to select ISTD.
After you've done that, you should be able to open your calibration table, and in the "Overview" view (and probably in others too) their is a column marked "ISTD" in which you can enter "Yes" for all peaks that are internal standards. For all other peaks, you can enter the number of the internal standard that you wish to use with them, and I think it goes in the column just to the right of ISTD.
One difficulty is that when you create a new calibration table, Chemstation defaults to assuming all exactly coeluting peaks are signals related to the same compound, so if you use it with mass spec and isotopically labelled internal standards, it will assume that the signal from the ISTD and target compound belong together (one will have a number in its "#" column of the cali table, and the other will be blank). To get round this, open the cali table and use "Insert" to add the 2nd compound manually.
Exporting everything to excel is very, very easy (once you know how!). If you open your sequence in the batch mode (this means looking for a file ending .b in the folder created when you ran the sequence; the file will have the same name as your sequence.s file, but will be sequence.b), then you can reprocess the sequence using whatever method you like (when you open the batch file it will offer you a chance to open it with another method, and it will ask you what files you want to process). You can set up the batch output options to include output to excel, or as csv, or whatever, and it's all completely automated. The disadvantage of post-processing is that all files are processed using the current calibration, so if you want to do bracketing, it's manual). If you need more detailed help, do ask. One warning: if you reprocess data using a different method, never ever save the batch file (or at least give it a new name). If you do so, you will never be offered the chance to choose a new method when you reopen it.
Alternatively, instead of using the built-in, reliable, easy and quick features of Chemstation, you can spend ages writing a macro, or trust someone else's dubious macro. It's amazing how many people buy software and then rewrite it instead of learning how it works.
