The reason that I am asking is that "response" in the calibration generated does not seem to be the area of peak of interest. I see the a huge peak of IS in the chromatogram and I also see the high number of "correct area"(i.e. 10982323) in percent report. However, when I generated calibration curve using that chromatogram, that response is very small (i.e. 80000) compared to other peaks which seems smaller than IS peak in the chromatogram. Any ideas?
Thanks!
Contact Dr. Chandan S. Chanotia, an experienced GC-MS scientist: https://www.researchgate.net/profile/Chandan_Chanotiya2/info
You must input the correct units into the calibration table (e.g. ng/ul), specify which peaks are sample, std or ignored (with the correct windows) and also choose the correct report style to view them in ChemStation. BTW: I can not see anything in the screen images you posted. They are all blurry.
Thanks for the comments William Letter. yes my unit is mg/ml since the unit of IS is mg/ml and I choose quantitation report to xls. What I don't understand is that why area or response of IS peak is different using auto integrate and calibration, which I generated. it is not slight change but it is a lot more than 10 times difference. PS. is it still blur if you clicked the pictures?
A few comments:
You indicate that you are exporting "data" to Excel. The area calculated using one set of integration parameters will generate one result. Are you exporting the report to Excel (not the raw data)? Does the data in the exported report match the data in the raw integration table found in the ChemStation report? Did you set up your calibration table correctly in ChemStation? This is critical for everything to make sense.
BTW: Yes, the images are still blurry. I can almost see the table where you have the calibration Levels and concentrations filled it. It is hard to read, but looks like you have filled in the the wrong info for the "Levels" and "Concentration" values. They appear backwards. Levels are the #'s assigned to each type of std, not the concentration values. Example: If you had five stds of one compound, then you would number their "levels" as: #1, #2, #3, #4 and #5. Across from each Level would be the concentration expressed in the units you have chosen. Another item that I am having trouble reading is the window values for each Rt specified. If these values are too narrow (or wide), then many errors can result. Their is no "right" value for these as the best values must be based on the chromatography obtained for the specific compound.
Hope this info is useful, but apologize if it is off the mark as I do not have much to go on.
Thanks for the useful comments William. No, the data exported report does not match with the data in the raw integration table. I think calibration table is somehow incorrect. I will look into things you commented. How do you set up the calibration then? Could you give me details explanation how you set up? Now, I am thinking my setting up is not quiet right although I followed the manual and youtube. Apologize if I am very new on GCMS to try to complete my master project.
Thank!
ChemStation multi-point calibration table construction is not difficult to learn, but you need the basics first. *It is critical to learn how the different data and detection settings effect the results. Chose poor voltage values, bad calibration window limits for Rt or use an unreliable method and your results will be unscientific at best. The easiest part is curve fitting. It is all of the other parameters that you need to learn first that make the process time consuming. Keep in mind, most people who run these systems have several years of training and experience with the instrument and software. Teaching someone how to do all of this is outside the scope of a web forum.
I strongly suggest one or more of the following options (in no particular order): Take a professional training class to learn ChemStation multi-point calibration; Study the built-in demo examples provided in the software and try and learn on your own; hire a consultant who can teach you on-site with your own system; find an employee at your school with some experience in creating ChemStation calibration tables who can help you learn the steps.
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