Chromatography Forum

Dear All
I have oil gas chromatogram in hard copy and the peak values in excel and I don’t have the chemstation file.

I need to calculate the area and height for another peak that did not include in my excel file. I could calculate the peak height from the response (Y axis) but I could not find a way to calculate the area.

Any help how to calculate the area of peak manually.

Thanks in advance.

You might have to go "old school" on this one.

If you have a paper copy of the chromatogram on standard copy paper. Cut a square of the paper (an area where there's no ink). If you know the surface area of your square, you can weigh the square on a balance. Now you know the cm^2/g for your paper.

Then, cut out the peaks (the one you know the Chemstation area for and your unknown). You can then use the known chemstation area, the cm^2/g for your paper, and the known masses for the cutouts of your peaks to determine what the chemstation area would have been for your unknown peak.

This is how we did it back in the day of strip-chart recorders (before pc's to acquire and manipulate data). Have fun!

You might have to go "old school" on this one.

If you have a paper copy of the chromatogram on standard copy paper. Cut a square of the paper (an area where there's no ink). If you know the surface area of your square, you can weigh the square on a balance. Now you know the cm^2/g for your paper.

Then, cut out the peaks (the one you know the Chemstation area for and your unknown). You can then use the known chemstation area, the cm^2/g for your paper, and the known masses for the cutouts of your peaks to determine what the chemstation area would have been for your unknown peak.

This is how we did it back in the day of strip-chart recorders (before pc's to acquire and manipulate data). Have fun!

That is definitely the easy manual way to do it. Of course the alternative would be to measure peak height, width, and slopes of the lines. Then manually do the integral to calculate a peak area for a known peak and the unknown peak and using the known peak's chemstation area calculate a conversion factor to calculate the chemstation area of the unknown peak.

Myself, I would stick with cut and weigh.

Or you could do a numerical integration of the peaks. Consider every data point within a peak to be a rectangle. Width = time between two datapoints, height = distance between baseline and datapoint. After that it's just a matter of calculating the surface of the rectangles and adding them all together.

Dear All
Thanks a lot for your help all of you.
All mentioned methods worked fine with me.
Thanks again.