Chromatography Forum

I am looking for an IC method development book....
This is what I am looking to learn:
I am developing a method for testing sweeteners via IC (I know there are a couple out there, but not with an ICS-5000)...just go with it. I need to figure out how many injections I need to make in order to prove that there is no significant difference in rt for an anaylte. So basically I need some stat help, but stats for chemistry.
Can anyone point me to a book or web site?
Thanks!!!

This should be right up your alley. In fact, they actually use ion chromatography for their examples:
http://www.americanlaboratory.com/1403- ... Chemistry/

Thank you so much!!!

I am at my wits end with this, and really hope someone can help.
I am trying to write my thesis on testing for artificial sweeteners by ion chromatography.
Where do I start? How many injections is enough to show no significant difference in RT for each compound? I have 4 compounds I am looking for.
My prof is not helpful at all, he makes me so frustrated and then I am worse off then when I spoke to him.
I have read as much as I can, but am making no headway.
How do you design experiments? Do you randomly pick a number? Are there calculations I should do?
I am quickly running out of time, so any help? Please.
Thanks!

Calculations for significance of difference are from statistics. If you know how much of a difference is the limit you can have and the standard deviation from a few injections, you can compute the number of injections required to be able to detect that difference. (the power of an experiment) Or the other way around with that is you can determine how likely you are to be able to detect a statistically significant difference with some practical number of injections.

Does that help?

The kind of statistics that you need is not specific to ion chromatography, or even to chemistry, it is just basic statistics. You need to compare the mean retention time of sets of injections under whatever different conditions you are experimenting on. You estimate the mean and the standard deviation from the raw data. A t test is probably what you need, but I am not sure that I understand what it is that you are trying to do - if there are no significant differences in the retention times of four compounds then you do not have a separation, and the method does not work.

Yes, there are calculations that you should do. You can do them with Excel.

Keep in mind that you can get large differences in retention time, but still not have statistical significance, if large variations in retention time are due to a poor method or sloppy operator technique. Two equally poor methods might not have a significant difference in retention if their retentions are not repeatable, but two good method with repeatable retentions might have a significant difference.

Peter