[manypostcards]

Hi,

My professor has tasked us with data analysis of a chromatogram but before we can do any of that we need to plot it. The y-axis (Response in mV) has been given to us in a text file however we need to fill in the time values. I have found a few ways to fill a spreadsheet column with lots of numbers but I can't get the retention times to line up with the peaks (a PDF of the chromatogram was given with retention times, peaks, etc.).

Here's a link to the PDF:

http://i.imgur.com/tLpFt.png

Here's the text file:

https://dl.dropbox.com/u/9196973/68D%2BFAEE%2B.8%2BmL-min.RAX

Any help is appreciated.

[Borek]

Looks like the data points are separated with a constant dt - take the last peak (the one around 4.7 minutes), find it in the data (somewhere around point 3600) and try to calculate dt. Anything wrong with this approach?

Edit: chances are dt is stated somewhere in the data description, I have not analyzed everything that is present in th etext file.

[manypostcards]

Borek, thank you for your reply. I also noticed that the points appear to be evenly spaced. How would I solve for dt without t values? Anything to get me started would be appreciated.

[Borek]

I told you - find the last peak in the data, it is around point 3600. You can read the time from the plot that you were given. Then you will know how many points were registered in how many minutes.

[manypostcards]

Are you suggesting to eyeball the width of the last peak and then go from there? And if so, that gave me another idea: why not subtract the retention times from two different peaks to find dt?

[Borek]

Are you suggesting to eyeball the width of the last peak and then go from there?

Not the width, but its retention time.

I assume both the text data and plot start at zero.

And if so, that gave me another idea: why not subtract the retention times from two different peaks to find dt?

That's more or less what I am talking about, but to get the smallest error possible you need to have them separated by as much as possible. So either take a first and last peak, or assume plot starts at zero like I did.

Actually it now occurred to me that you an also try to assume data in the text file simply starts at zero and ends at 5.3

[manypostcards]

BRILLIANT! Thank you!